liposomes, niosomes and nanotechnology

PAPER – 930102 CHAPTER – 5 LIPOSOMES,NIOSOMES

& NANOTECHNOLOGY

LIPOSOMES, NIOSOMES AND NANOTECHNOLOGY

GUIDED BY: - Dr. R. K. Parikh PRESENTED

BY:- Jignasha R. Bhuria M. Pharm Sem-III Batch:2010 Roll no:-05

DEPARTMENT OF PHARMACEUTICS AND PHARMACEUTICAL TECHNOLOGY, L.M.COLLEGE OF PHARMACY.

L.M.COLLEGE OF PHARMACY,AHMEDABADPage 37


& NANOTECHNOLOGY

CONTENTS 1. Definition2. Why Use Liposomes?3. Classification of Liposomes4. Manufacturing of Liposomes 4.1 Materials 4.2 Issues to Consider while Selecting Lipids 4.3 Mechanism of Liposome Preparation 4.4 Methods of Liposome Preparation 4.5 Drug Loading into Liposomes5. Quality Control Assays of Liposomal Products6. Drug Release from Liposomes7. Pharmaceutical Technology: Hurdles8. Recent Advances9. Chemical Abstracts10. Liposomal based Pharmaceuticals in Market or in Clinical trials

DEFINITION Definition of Liposome: A liposome is a microvesicle composed of a bilayer of

lipid amphipathic molecules enclosing an aqueous compartment. Liposome Drug Products (LDPs) are formed when a liposome is used to

encapsulate a drug substance either within the lipid bilayer or in the interior aqueous space of the liposome.

Liposomes are microscopic spheres made from fatty materials, predominantly phospholipids.

Liposomes are made of molecules with hydrophilic and hydrophobic ends that form hollow spheres which can encapsulate water-soluble ingredients in their inner water space and oil-soluble ingredients in their phospholipid membranes that are made up of one or more concentric lipid bilayers, and range in size from 50 nanometers to several micrometers in diameter.


Fig. 2 A micrograph view of a liposome.


& NANOTECHNOLOGY

WHY USE LIPOSOMES ? Direction:

Liposomes can target a drug to the intended site of action in the body, thus enhancing its therapeutic efficacy (drug targeting, site-specific delivery).

Liposomes may also direct a drug away from those body sites that are particularly sensitive to the toxic action of it (site-avoidance delivery).

Duration: Liposomes can act as a depot from which the entrapped compound is slowly

released over time. Such a sustained release process can be exploited to maintain therapeutic (but nontoxic) drug levels in the bloodstream or at the local administration site for prolonged periods of time.

Thus, an increased duration of action and a decreased frequency of administration are beneficial consequences.

Protection: Drugs incorporated in liposomes, in particular those entrapped in the aqueous

interior, are protected against the action of detrimental factors (e.g. degradative enzymes) present in the host.

Conversely, the patient can be protected against detrimental toxic effects of drugs

Internalization: Liposomes can interact with target cells in variousways and are therefore able to

promote the intracellular delivery of drug molecules that in their ‘free’ form (i.e. non-encapsulated) would not be able to enter the cellular interior due to unfavorable physicochemical characteristics (e.g. DNA molecules).

L.M.COLLEGE OF PHARMACY,AHMEDABAD9


& NANOTECHNOLOGY

Amplification: If the drug is an antigen, liposomes can act as immunological adjuvant in vaccine

formulations. CLASSIFICATION OF LIPOSOMES

Based on Composition & Application:

i) Conventional liposomes These can be defined as liposomes that are typically composed of only

phospholipids (neutral and/or negatively charged) and/or cholesterol. Most early work on liposomes as a drug-carrier system employed this type of liposomes.

Conventional liposomes are a family of vesicular structures based on lipid bilayers surrounding aqueous compartments.

Conventional liposomes are characterized by a relatively short blood circulation time due to rapid uptake by MPS system.

They are useful for macrophage targeting, as local depot and for vaccination purpose.

ii) Long-circulating liposomes The fast and efficient elimination of conventional liposomes from the circulation

by liver and spleen macrophages has seriously compromised their application for the treatment of the wide range of diseases involving other tissues.

The advent of new formulations of liposomes that can persist for prolonged periods of time in the bloodstream led to a revival of interest in liposomal delivery systems at the end of the 1980s.

In fact, the long-circulating liposomes opened a realm of new therapeutic opportunities that were up to then unrealistic because of efficient MPS uptake of conventional liposomes.

Perhaps the most important key feature of long circulating liposomes is that they are able to extravasate at body sites where the permeability of the vascular wall is increased. Fortunately, regions of increased capillary permeability include pathological areas such as solid tumors and sites of infection and inflammation.

L.M.COLLEGE OF PHARMACY,AHMEDABAD0


& NANOTECHNOLOGY

It is illustrative for the importance of the long-circulation concept that the only two

liposomal anticancer products that are approved for human use are based on the use of long-circulating liposomes for tumor-selective delivery of antitumor drugs (Doxil,DaunoXome).

At present the most popular way to produce long-circulating liposomes is to attach hydrophilic polymer polyethylene glycol (PEG) covalently to the outer surface.

iii) Immunoliposomes Immunoliposomes have specific antibodies or antibody fragments (like Fab9 or

single chain-antibodies) on their surface to enhance target site binding. They are useful for site specific targeting.

iv) Cationic liposomes These delivery systems are under development for improving the delivery of

genetic material. Their cationic lipid components interact with, and neutralize, the negatively-

chargedDNA, thereby condensing the DNA into a more compact structure. The resulting lipid–DNA complexes, rather than DNA encapsulated within liposomes, provide protection and promote cellular internalization and expression of the condensed Plasmid.

v) Temp.-sensitive immunoliposomes The heat induced drug release concept is based on the large increase in the

permeability of liposomal bilayers around their phase transition temperature. Local heating of tumor tissue up to this phase transition temp. will enhance drug

release from liposomes present in the heated area. Both the degree of extravasation and the rate of drug release increases in this case.

vi) pH-sensitive immunoliposomes pH sensitive IL targeted to internalizing receptors will end up in endosomes,

where acidification will trigger liposome destabilization and possible fusion with endosomal membrane.

They have been successfully applied in vitro for the delivery of antitumor drugs into cytoplasm of tumor cells.



& NANOTECHNOLOGY

Based on Pharmaceutical Aspects:

MANUFACTURING OF LIPOSOMES Materials Issues to Consider while Selecting Lipids Mechanism of Liposome Preparation Methods of Liposome Preparation Drug Loading into Liposomes

Materials

Various lipids and amphiphiles are available as liposome raw materials or additives that are required for the formation of lipid bilayers.

Phospholipids Synthetic Phospholipids Glycerolipids Sphingolipids Glycosphingolipids Steroids



& NANOTECHNOLOGY

Polymeric material Charge-inducing lipids

PhospholipidsNatural Phospholipids: Phosphotidylcholine Phosphotidylserine Phosphotidylethanolamine Phosphotidylinositol Synthetic Phospholipids:1, 2-Dilauroyl-sn-Glycero-3-Phosphocholine (DLPC)1, 2-Dioleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (DOPS)Dipalmitoylphosphotidylcholine DistearoylphosphotidylcholineDipalmitoylphosphotidylserineDipalmitoylphosphotidylglycerol1,2-Dilauroyl-sn-Glycero-3-Phosphocholine (DLPC)Unsaturated 1-Stearoyl-2-Linoleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt)Dioleaylphosphotidylcholine

Sphingolipids: Shingomyelin Glycosphingolipids: Gangliosides Steroids: Cholesterol Polymeric material: Lipids conjugated to diene, methacrylate,& thiol group Charge-inducing lipids: Dioctadecyldimethyl ammonium bromide/chloride (DODAB/C) Dioleoyl trimethylammonium propane (DOTAP ) Other Substances: Stearylamine & Dicetylphosphates, Polyglycerol & polyethoxylated mono & dialkyl amphiphiles

Issues to Consider while Selecting Lipids:

1. Phase transition temperature



& NANOTECHNOLOGY

The phase transition temperature is defined as the temperature required to

induce a change in the lipid physical state from the ordered gel phase, where the hydrocarbon chains are fully extended and closely packed, to the disordered liquid crystalline phase, where the hydrocarbon chains are randomly oriented and fluid.

There are several factors which directly affect the phase transition temperature including hydrocarbon length, unsaturation, charge, and headgroup species.

When developing a new product, procedure, or method, controlling the transition temperature of the lipid could be useful.

Using a high transition lipid when filtration is necessary could present some technical problems.

2. Stability The long term stability or shelf-life of a drug product containing lipids can be

dramatically affected by the lipid species used in the formulation. Generally, the more unsaturated a compound, the easier the product is oxidized, and thus the shorter the shelf life of the product.

Lipids from biological sources (e.g., egg, bovine, or soybean) typically contain significant levels of polyunsaturated fatty acids and therefore are inherently less stable than their synthetic counterparts.

While saturated lipids offer the greatest stability in terms of oxidation, they also have much higher transition temperatures and thus present other difficulties in formulation.

3. Charge The charge is generally imparted by the presence of anionic phospholipid

species in the membrane. The major naturally occurring anionic phospholipids are phosphatidylserine, phosphatidylinositol, phosphatidic acid, and cardiolipin.

The charge may provide a special function for the membrane. Several steps of the blood coagulation cascade require a lipid membrane. The assembling of protein aggregates on the surface of platelets requires a negatively charged surface.

4. Lipid mixtures In many cases, a single lipid species does not yield the exact physical

properties needed for a particular system, or does not adequately mimic the natural system for which it is intended to replace or reproduce.

For these issues, consider a complex lipid mixture composed of two or more individual lipid species, the composition designed to create or reproduce a particular charge ratio, unsaturation ratio, phase transition temperature, or biological function.

5. CholesterolCholesterol is a membrane constituent widely found in biological systems which serves a unique purpose of modulating membrane fluidity, elasticity, and permeability.



& NANOTECHNOLOGY

It literally fills in the gaps created by imperfect packing of other lipid species

when proteins are embedded in the membrane. Unfortunately, cholesterol presents certain problems when used in human

pharmaceuticals. Purity sources Stability problem for lipid based drug products

6. Source There are two basic sources of phospholipids: synthetic and tissue-derived.

Tissue-derived lipids are generally either egg-derived or bovine-derived. For clinical applications, either of these sources is not suitable due to stability

problems and the possibility of viral or protein contamination. The U.S. Food and Drug Administration issued a letter restricting the source

of bovine tissue used to isolate pharmaceutical products to countries and animals certified to be free of bovine spongiform encephalopathy (BSE).

Egg sources are not currently restricted, however, additional testing for viral contamination may be required for pharmaceutical products.

Mechanism of Liposome Preparation:

1. The budding theory Stress induced hydration of phospholipids. Organization in to lamellar arrays. Results in to budding of lipid bilayer leading to down sizing.

2. The bilayer phospholipids theory.

Liposomes (lipid vesicles) are formed when thin lipid films or lipid cakes are hydrated and stacks of liquid crystalline bilayers become fluid and swell.

The hydrated lipid sheets detach during agitation and self-close to form large, multilamellar vesicles (LMV).

Once these particles have formed, reducing the size of the particle requires energy input in the form of sonic energy (sonication) or mechanical energy (extrusion).

4. Methods of Liposome Preparation:



& NANOTECHNOLOGY

Properties of liposomal formulations can vary depending on the composition (cationic, anionic, neutral lipid species) and method of preparation. Reproducible results can be obtained only with validated SOPs in combination with appropriate quality control procedures.

Steps involved in preparation of liposomes are as follow:a. Preparation of lipid for hydrationb. Hydration of lipid film/cakec. Sizing of lipid suspension

i. Sonication ii. Extrusion

Methods of Preparation

Conventional liposome preparation methods. Traditionally, the series of sequential unit processes is followed to produce

liposomes. First the bilayer forming elements are mixed in volatile organic solvent or

solvent mixture. eg. Chloroform, ether, ethanol, or a combination of these. Solution of lipid components is prepared and filtered to remove minor

insoluble components. Ultrafilterred to lower pyroburden. Solvent is subsequently removed under conditions like pressure and

temperature that ensures that no phase separation of the components of mixture take place.

The obtained dry lipid mixture is hydrated by exposure to an aqueous medium containing dissolved solutes, including buffer, salts, chelating agents and drugs to be entrapped.

Liposomes produced during hydration are generally heterogeneous in size that can be “down sized” extrusion or mechanical fragmentation.

Now the uncapsulated drug is removed by various techniques like – centrifugation, dialysis or diafiltration.

The product is passed through sterile filters (0.22 micron) to ensure removal of any bacteria that might be present.


http://www.avantilipids.com/extruder.html

http://www.avantilipids.com/UltrasonicCleaner.html

PhospholipidsCholesterol Antioxidant

Lipid component compounding Lipid solvent

Pyrogen Ultrafilteryes

No

Filter

Solvent removal

Drug Salt Antioxidant Buffer WFI

Filter

HydrationSolvent recovery

Extrusion Down sizing

Free drug removal

Prefilter

Sterile filter

Vial filling

Free drug recovery

Aseptic processingLyophollization seal packageSeal / package


& NANOTECHNOLOGY

Methods for preparation of small unilamellar vesicles (SUV)1 Sonication.2 High shear fragmentation.

.3 Solvent injection method.a. Injection of water immiscible solvent. i. Ether infusion ii. Fluorocarbon injection b. Injection of water miscible solvent. i. Ethanol injection. ii. Modified ethanol injection method.

Sonication


Aqueous samples

Piston

Cell body

Rubber-O-ring

Closure plug

Pressure relief valve valve

Outlet

Fig. French pressure cell


& NANOTECHNOLOGY

MLV, Oligolamellar vesicles or LUV preparations obtained by other methods

are sonicated to form SUVs. Sonication is carried out either with a batch sonicator or a probe sonicator

under an inert atmosphere. Disadvantages with use of sonicators.

Particle sheddingDifficulty with energy regulationHeat-exchange problemsHeat productionDegradation of lipids

High shear fragmentation Dispersion of MLVs can be converted into SUVs by passage through a small

orifice under high pressure. French pressure cell is used. An MLV dispersion is placed in the French press and extruded at about

20,000 PSI at 4C. Multiple extrusion results into progressive decrease in the mean particle

diameter. Reciprocating piston homogenizers are also used to produce SUVs.

Solvent injection methoda) Injection of water immiscible solvent

This method includes injection of water immiscible solvents containing a mixture of bilayer forming lipids in to aqueous medium.

Produce relatively uniform unilamellar and oligolamellar vesicles.

i) Ether infusion Liposomes are prepared by slowly introducing a solution of lipids dissolved in

diethyl ether in to warm water. The lipid mixture is injected into an aqueous solution of the material to be

encapsulated by using a syringe type infusion pump at 55- 65C or under reduced pressure.


TB

Vacuumpump

Mix

Gasket

Ether/lipidsolution

Mechanical drive

Infusion pump

Aqueousphase


& NANOTECHNOLOGY

TB: - Temperature controlled bathii) Fluorocarbon injection

To overcome the hazardous associated with diethyl ether the fluorocarbon solvents are used for injection. Eg. Freon 21 (CHFCl2).

The advantage over ether infusion method includes- Useful for heat liable molecules because the solvent is infused into

cool water under lower pressure.

b) Injection of water miscible solvent Water miscible solvents such as ethanol, glycerin and polyglycols are used. Principle :-

During infusion the solvent containing the lipid is diluted by an excess amount of aqueous phase.

As solvent concentration reduces liposomes formed.

i) Ethanol Injection Ethanol is used to dissolve the lipids and solution is rapidly injected into an

excess of buffer solution. SUVs form spontaneously. Method is restricted to the production of relatively dilute SUVs suspension. Removal of residual ethanol is also present a problem. This can be done by

ultrafilteration or vacuum distillation.

ii) Modified ethanol injection method A modified ethanol injection method for liposomes containing soybean

phosphatidylcholine (SPC), cholesterol (Ch), ß-sitosterol ß-D-glucoside (Sit-G) and oleic acid (OA) was developed, that can produce homogeneous unilamellar liposomes without the use of sonication and dialysis.

In this method, water is poured into a concentrated lipid-ethanol solution and then ethanol is removed in an evaporator.

Dilution with water causes spontaneous formation of small and homogenous unilamellar vesicles from micellar aggregate.



& NANOTECHNOLOGY

iii) Other water miscible solvents Polyhydric alcohols such as glycerol, polyglycerol, propylene glycol, ethylene

glycol and glycerol esters such as monolectins are useful as lipid solvent and in preparation of liposomes.

Advantages with use of water miscible solvents These organic solvents are relatively safe. They can be left in formulation. Protect the product during freezing.

Large and Intermediate sized unilamellar vesicles (LUVs and IUVs) LUV means any structure larger than 100 nm. LUV means vesicles bounded by a single bilayer membrane that are above

100 nm in diameter.Methods used to prepare LUV and IUV

Detergent dialysis. Water in oil emulsion technique. Freeze thaw cycling. Slow swelling in non electrolytes. Dehydration followed by rehydration. Dilution or dialysis of lipids in the presence of chaotropic ions.

1 . Detergent dialysis or Detergent Removal method The detergent depletion method is used for preparation of a variety of

liposomes and proteoliposome formulations. Detergents can be depleted from a mixed detergent-lipid micelles by various

techniques which leads to the formation of very homogeneous liposomes The most popular detergent is sodium cholate, alkyl(thio)glucoside, and

alkyloxypolyethylenes. The use of different detergents results in different size distributions of the

vesicles formed. A faster depletion rate produces smaller size liposomes. The use of different detergents also results in different ratios of large

unilamellar vesicles/ oligolamellar vesicles/multilamellar vesicles.

Detergent depletion is achieved by of four following approaches:I. Dialysis: The dialysis can be preformed in dialysis bags immersed in large

detergent free buffers (equilibrium dialysis) or by using continuous flow cells, diafiltration and cross filtration.

II. Gel filtration: In this method the detergent is depleted by size exclusive chromatography. Sephadex G-50, Sephadex G-100, Sepharose 2B-6B and Sephacryl S200-S1000 can be used for gel filtration. The liposomes do not penetrate into the pores of the beads packed in a column.

III. Adsorption: Detergent adsorption is achieved by shaking of mixed micelle solution with beaded organic polystyrene adsorbers such as XAD-2 beads and Bio-beads SM2. The great advantage of the using detergent adsorbers is that


Lipid in solvent solventsolvent solution

Two-phase system Water in oil

emulsion

Solvent removal removalGel formation formationREV liposomes


& NANOTECHNOLOGY

they can remove detergents with a very low critical micelle concentration (CMC) which are not completely depleted by dialysis or gel filtration methods.

IV. Dilution: Upon dilution of aqueous mixed micellar solution of detergent and phospholipids with buffer the micellar size and the polydispersity increases dramatically, and, as the system is diluted beyond the mixed micellar phase boundary, a spontaneous transition from polydisperse micelles to monodisperse vesicles occurs.

2. Reverse phase evaporation techniqueThe phospholipids are first dissolved in organic solvent (either single or a

mixture of solvents) having same density as that of water for easy emulsification. The compound to be entrapped present in aqueous phase is added directly to the phospholipids solvent mixture.

Two phases are emulsified by sonication to form w/o emulsion and then organic phase is removed slowly under partial vacuum( so, called reverse phase evaporation)Mechanism involved in liposome formation is given below.

4.4.3.3 High pressure extrusion. MLVs on repeated extrusion through very small pore diameter polycarbonate

membrane under high pressure produces intermediate sized unilamellar vesicles.



& NANOTECHNOLOGY

4. Freeze drying SUVs dispersion. Freeze-dried liposomes are formed from preformed liposomes. Very high

encapsulation efficiencies even for macromolecules can be achieved using freeze-dried hydration method.

The aqueous phase containing the molecules to be encapsulated is mixed with preformed suspension of SUVs and the mixture is freeze dried by conventional means.

Large MLVs are formed when the dry lipid is rehydrated, usually with a small volume of distilled water.

Drug Loading into Liposomes:

1 Encapsulation The physicochemical properties of the drug itself, especially solubility and

partition coefficient, are important determinant of the extent of its incorporation in liposomes.

It is useful for water-soluble drugs (doxorubicin, penicillin G), the encapsulation is simple hydration of a lipid with an aqueous solution of drug.

The formation of liposomes passively entraps dissolved drug in the interlamellar spaces, essentially encapsulating a small volume.

2 Partitioning A drug substance that is soluble in organic solvents (cyclosporine) will go

through partitioning. It is dissolve along with phospholipid in a suitable organic solvent.

This combination is dried first after than added directly to the aqueous phase and solvent residues remove under vacuum. The acyl chains of the phospholipids provide a solubilizing environment for the drug molecule. This will be located in the intrabilayer space.

3 Reverse loading The reverse-loading mechanism uses for certain drugs (5-fluorouracil,

mercaptopurine) may exist in both charged and uncharged forms depending on the ph of the environment.

This type of drug can be added to an aqueous phases in the uncharged state to permeate into liposomes through their lipid bilayers. Then the internal pH of the liposome is adjusted to create a charge on the drug molecules.



& NANOTECHNOLOGY

Once, charged the drug molecules no longer is lipophilic enough to pass

through the lipid bilayer and return to the external medium.

QUALITY CONTROL ASSAYS OF LIPOSOMAL PRODUCTS



& NANOTECHNOLOGY

DRUG RELEASE FROM LIPOSOMES

The lipid bilayer of the liposome can fuse with other bilayers (e.g. cell membrane) thus delivering the liposome contents. By making liposomes in a solution of DNA or drugs (which would normally be unable to diffuse through the membrane) they can be delivered past the lipid bilayer.

PHARMACEUTICAL TECHNOLOGY: HURDLES



& NANOTECHNOLOGY

Raw materials:

Phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) from natural sources are often used as phospholipids for parenteral liposome preparations. These phospholipids have a source-dependent composition of acyl chains and in some cases also batch dependent. In the early 1980s the quality of lipids of several suppliers could vary considerably; both in quantitative and qualitative terms. Nowadays, a few suppliers provide the global market with high-quality products. Quality is ensured by improved purification schemes, the introduction of validated analytical techniques and a better insight into lipid degradation mechanisms.

Physicochemical properties: Liposome behavior in vitro and in vivo strongly depends on their size,

bilayer rigidity, charge and morphology (i.e. unilamellar, multilamellar, multivesicular).

Therefore, a full physicochemical characterization of pharmaceutical liposomes is required in early stages of research.

In a later development stage, the outcomes of the listed quality control assays can be used to obtain regulatory approval for the liposome product. A selection can then be used to ensure batch-to-batch consistency.

Pay load: After finishing the hydration stage of the liposome preparation process,

non- liposome-associated drug is removed. Polar drugs and drugs that don’t have an electric charge opposite to the

(usually negatively charged) bilayer show poor encapsulation after hydrating the lipids: there is ‘a pay load’ problematic.

Shelf- life: For a pharmaceutical product, a minimum shelf-life of two years,

preferably without refrigerator cooling, is a primary requirement. Liposome shelf-life may be limited because of two factors. First, physical

instability – drug leakage from or through the bilayer and liposome aggregation or fusion.Second, chemical instability – hydrolysis of the ester bonds or oxidation of unsaturated acyl groups.

Oxidation can be prevented by excluding oxygen from the injection vial, by addition of an anti-oxidant (e.g. vitamin E) or by selection of saturated acyl-chains in the phospholipid.

Minimizing hydrolysis is possible by selecting an environmental pH of 6.5 and low temperatures. If those conditions cannot be met, (freeze) drying may be considered. Liposomes can be successfully freeze dried if the proper lyoprotectant is used and proper freeze-drying conditions are chosen.

Disaccharides are excellent lyoprotectants. They prevent aggregation and fusion upon reconstituting the cake.



& NANOTECHNOLOGY

Scale-up:

Most of above mentioned methods are useful for only lab-scale liposome preparation. If possible, the use of a high shear homogenizer for the production of small vesicles is a first choice. No organic solvents are required to dissolve the lipids first, nor are detergents necessary to hydrate the lipids, and there is easy access to the appropriate (commercially available) equipment.

Issues that are related to the parenteral administration of liposomes are the product sterility and the absence of pyrogens.

The preferred way of sterilizing liposomes is by autoclaving. This is a realistic option; if the pH conditions are optimal, the drug is heat stable and lipophilic. Otherwise, reliance on filtration through membranes with 0.2 mm pores or aseptic production procedures are necessary.

Standard procedures for pyrogen-free production of parenterals can be utilized.Limulus amoebocyte lysate (LAL) tests on pharmaceutical liposomes should be thoroughly validated.

Safety data: For the present generation of pharmaceutical liposomes containing highly potent drugs with a narrow therapeutic window (e.g. cytostatics and fungicides) no safety problems directly related to the liposomes have been observed. However, changes in their side-effect profile may occur. For example, the ‘hand-and- foot’ syndrome (see below) observed after administration of long-circulating doxorubicin liposomes is not found after administration of free doxorubicin in standard protocols.

Approved Liposome Drug Products

RECENT ADVANCES

1. Provesicles in drug delivery systemsTo overcome the limitations (especially chemical and physical stability) of

vesicular drug delivery systems like liposomes, niosomes, transferosomes, and pharmacosomes, provesicular approach was introduced.This includes-

1.1 Proliposomes



& NANOTECHNOLOGY

Proliposomes are the products which are mixed with water phase containing

drug before use, liposomes formed automatically and load the drug. Three different types of proliposomes are formulated.

1.2 Dry granular liposomes Dry, free flowing granular product, which can be hydrated immediately before

use. Composed of water soluble porous powder coated with drug and lipids. Dry granular type of liposomes has been studied for effective delivery of

various drugs like 5-fluorourasil, ibuprofen, indomethacin, adriamycin, doxorubicin, glyburide, and hydrocortisone.

1.3 Mixed micellar proliposomes Mixed micelles contain bile salts, cholesterol, and phospholipids, which upon

dilution, undergo micelles to vesicle transition to form liposomes. Liquid crystalline proliposomes. Involves organization of lipid/ethanol/water mixture into lamellar structure.

1.4 Protransferosomes Protransferosomes are proultraflexible vesicles, which can be converted into

ultraflexible vesicles.

1.5 Characterization of provesicular system Morphology. Angle of repose. Size and size distribution. Rate of hydration. Entrapment efficiency. Degree of deformability and permeability measurement. In vitro release rate. In vivo fate and pharmacokinetic.

2. Lipopolyplexes A combination of DNA, polymers and liposomes has been prepared with a

view to enhance transfection ability by utilization of their individual properties. It has been reported that this method has resulted in better gene transfer and

lower toxicity as compare to cationic liposomes alone.3. Transferosomes

Modified liposomes developed to increase the transdermal permeation of drug.

Deformability is achieved by using surface active agent in proper ratio. Concentration of surfactant is very crucial because at sublytic conc. This

agent provides flexibility of transferosomal membrane and at higher conc. Cause destruction of vesicles.

4. Ethosomes

Ethosomes are soft, malleable vesicles composed mainly of phospholipids, ethanol (relatively high concentration) and water.



& NANOTECHNOLOGY

These “soft vesicles” represents novel vesicular carrier for enhanced delivery to/through skin. The size of Ethosomes vesicles can be modulated from tens of nanometers to microns.

Ethosomes are provides a number of important benefits including improving the drug's efficacy, enhancing patient compliance and comfort and reducing the total cost of treatment. The Ethosomes were found to be suitable for various applications within the pharmaceutical, biotechnology, veterinary, cosmetic, and nutraceutical markets.

Mechanism Of Drug Penetration

The enhanced delivery of actives using ethosomes over liposomes can be ascribed to an interaction between ethosomes and skin lipids. A possible mechanism for this interaction has been proposed. It is thought that the first part of the mechanism is due to the ‘ethanol effect’, whereby intercalation of the ethanol into intercellular lipids increasing lipid fluidity and decreases the density of the lipid multilayer 5 . This is followed by the ‘ethosome effect’, which includes inter lipid penetration and permeation by the opening of new pathways due to the malleability and fusion of ethosomes with skin lipids, resulting in the release of the drug in deep layers of the skin, shown in Figure 1.

Fig. 1 Mechanism of penetration of ethosomal drug delivery system

Preparation And Characterization

Ethosomes can be prepared from soybean phosphatidylcholine (Phospholipon 90), ethanol, drug and distilled water. Phospholipon 90 and drug should be dissolved in ethanol. Water has to be added in small quantities and the preparation mixed by mechanical stirring under controlled conditions 6 .

Various methods for characterization of Ethosomes

1. Visualization: Visualization of ethosomes can be done using transmission electron microscopy (TEM) and by scanning electron microscopy (SEM) 7 .

2. Vesicle size and Zeta potential: Particle size and zeta potential can be determined by dynamic light scattering (DLS) using a computerized inspection system and photon correlation spectroscopy (PCS) 8 .

3. Entrapment Efficiency: The entrapment efficiency of drug by ethosomes can be measured by the ultracentrifugation technique 9 .



& NANOTECHNOLOGY

4. Transition Temperature: The transition temperature of the vesicular lipid

systems can be determined by using differential scanning calorimetry 6 . 5. Surface Tension Activity Measurement: The surface tension activity of drug

in aqueous solution can be measured by the ring method in a Du Nouy ring tensiometer 10 .

6. Vesicle Stability : The stability of vesicles can be determined by assessing the size and structure of the vesicles over time. Mean size is measured by DLS and structure changes are observed by TEM 11 .

7. Drug Content : Drug can be quantified by a modified high performance liquid chromatographic method 12 .

8. Penetration and Permeation Studies: Depth of penetration from ethosomes can be visualized by confocal laser scanning microscopy (CLSM) 13 .

Advantages of Ethosomal Drug delivery

In comparison to other transdermal & dermal delivery systems,

1. Ethosomes are enhanced permeation of drug through skin for transdermal and dermal delivery.

2. Ethosomes are platform for the delivery of large and diverse group of drugs (peptides, protein molecules)

3. Ethosome composition is safe and the components are approved for pharmaceutical and cosmetic use.

4. Low risk profile- The technology has no large-scale drug development risk since the toxicological profiles of the ethosomal components are well documented in the scientific literature.

5. High patient compliance- The Ethosomal drug is administrated in semisolid form (gel or cream), producing high patient compliance by is high. In contrast, Iontophoresis and Phonophoresis are relatively complicated to use which will affect patient compliance.

6. High market attractiveness for products with proprietary technology. Relatively simple to manufacture with no complicated technical investments required for production of Ethosomes.

7. The Ethosomal system is passive, non-invasive and is available for immediate commercialization.

8. Various application in Pharmaceutical, Veterinary, Cosmetic field.

Table 1 Ethosomes as a carrier of various drug molecules has been listed below.

Drug Applications Comments Ref.



& NANOTECHNOLOGY

Acyclovir Treatment of Herpetic infection

Improved drug delivery 14

Zidovudine Treatment of AIDS Improved transdermal flux 15 Trihexypenidyl HCl

Treatment of Parkinsonian syndrome

Increased drug entrapment efficiency, reduced side effect & constant systemic levels

12,16

Erythromycin Efficient healing of S.

aureus -induced deep dermal infections

Improved drug penetration and systemic effect.

17

Insulin Treatment of Diabetes Improved therapeutic efficacy of drug

19

Testosterone Treatment of male hypogonodism

Enhance skin permeation 20

Cannabidol Prevents inflammation and edema

Significant accumulation of the drug in the skin

21

Minodixil Hair growth promotion effect

Higher skin retention 23

Bacitracin Treatment of dermal infections

Reduced drug toxicity 24

Conclusion

Ethosomes are soft, malleable vesicles and potential carrier for transportation of drugs. Ethosomes are characterized by simplicity in their preparation, safety and efficacy and can be tailored for enhanced skin permeation of active drugs. Ethosomes have been found to be much more efficient at delivering drug to the skin, than either liposomes or hydroalcoholic solution. Ethosomes have been tested to encapsulate hydrophilic drugs, cationic drugs, proteins and peptides. Ethosomal carrier opens new challenges and opportunities for the development of novel improved therapies.

5. Discosomes Small et al first observed discoidal mixed micelle in phase behavior of PC in

cholate-water system.

6. Virosomes Reconstituted lipid vesicles equipped with viral glycoprotein is used for DNA

transfer.

7. Emulsomes New generation colloidal drug carrier unit. The emulsomes can be explicitly distinguished from fat emulsion or lipid

microsphere as they are distinctively sphere vesicular graft like system due to utilization of higher quantities of PC both as emulsifying agent as well as surface modifier.



& NANOTECHNOLOGY

8. Cochleates

Cochleates are cigar-like microstructures that consist of a series of lipid bilayers which are formed as a result of the condensation of small unilamellar negatively charged liposomes.

In the presence of calcium, the small phosphatidylserine (PS) liposomes fuse and form large sheets.

These sheets have hydrophobic surfaces and, in order to minimize their interactions with water, tend to roll-up into the cigar-like cochleate.

Discovered in 1975 by Dr. D. Papahadjoupoulos.

9. Depofoam technology Depofoam particles include hundred of bilayer enclosed aqueous compound. Formed by first emulsifying a mixture of an aq. phase containing the

compound to be encapsulated & an organic phase containing lipid. The first emulsion is then dispersed & emulsified in a 2nd aq phase. After the organic solvent is evaporated, numerous submicron to micrometer

sized water compartment are separated by lipid layer & take on a closed packed polyhedral structure From which the comp slowly permeate.

CHEMICAL ABSTRACTS

146:50369f Spray freeze dried liposomal ciprofloxacin powder aerosol drug delivery

Ciprofloxacin is mixed with a phospholipid to form a liquid liposome suspension.

After preparing suspension, it is spray freeze dried to prepare powder for inhalant aerosol delivery.

146:148621g In vitro evaluation of enrofloxacin-loaded MLV liposomes Liposomes are prepared by dry lipid film method. Fluoroquinolones are broad spectrum antibiotics that requires to reach intracellular target site (DNA gyrase) in E. coli by means of an uptake

process through outer & inner membranes. Delivery of quinolones with liposomes represented excellent

advantages of improving the selective transport of antibiotics as compared to free drug.



& NANOTECHNOLOGY

147:263117e Liver targeted resveratrol liposomes This was used to prepare resveratrol liposome (RES-LIP) and the

liposomes modified by a galactose (RES-GLIP) as well as to investigate and compare their liver targeting effect.

RES-GLIP showed a good liver targeted efficiency in vivo, which may reduce the side effects of RES, decrease dose and improve its efficiency.

146:487345v Liposomes as adjuvant for combination vaccines Tetanus toxoid (TT) loaded liposomes and diphtheria toxoid loaded

liposomes were prepared by reverse phase evaporation method and after combining these two vaccines the potential advantages were investigated.

The results showed that immune response of TT increased when it was combined with DT in liposomes.

147:58071u Influence of poly(ethylene glycol) grafting density and polymer length on liposomes: Relating plasma circulation life times to protein binding

It prolongs circulation lifetime of liposomes. Mechanism is not fully elucidated. But it is believed that PEG-lipids

mediate steric stabilization, ultimately reducing surface-surface interactions including the aggregation of liposomes and/or adsorption of plasma proteins.

Limitations Unable to cross the capillary endotherial cells in most organs except the liver Many cell types have a limited capacity to phagocytose particles like

liposomes

NIOSOMES

CONTENTS

1. Introduction2. Structure of Niosomes3. Method of Preparation of Niosomes4. Drugs incorporated into niosomes by various

methods5. Advantages of Niosomes6. Comparison of Niosome v/s Liposome7. Characterization of niosomes



& NANOTECHNOLOGY

8. Applications of Niosomes9. Marketed Products

INTRODUCTION:

Niosomes are a novel drug delivery system, in which the medication is encapsulated in a vesicle. The vesicle is composed of a bilayer of non-ionic surface active agents and hence the name niosomes. The niosomes are very small, and microscopic in size. Their size lies in the nanometric scale. Although structurally similar to liposomes, they offer several advantages over them. Niosomes have recently been shown to greatly increase transdermal drug delivery and also can be used in targeted drug delivery, and thus increased study in these structures can provide new methods for drug delivery.

Structure of Niosomes: Niosomes are microscopic lamellar structures, which are formed on the

admixture of non-ionic surfactant of the alkyl or dialkyl polyglycerol ether class and cholesterol with subsequent hydration in aqueous media.

Structurally, niosomes are similar to liposomes, in that they are also made up of a bilayer. However, the bilayer in the case of niosomes is made up of non-ionic surface active agents rather than phospholipids as seen in the case of liposomes. Most surface active agents when immersed in water yield micellar structures, however some surfactants can yield bilayer vesicles which are niosomes.

Niosomes may be unilamellar or multilamellar depending on the method used to prepare them.The niosome is made of a surfactant bilayer with its hydrophilic ends exposed on the outside and inside of the vesicle, while the hydrophobic chains face each other within the bilayer. Hence, the vesicle holds hydrophilic drugs within the space enclosed in the vesicle, while hydrophobic drugs are embedded within the bilayer itself. The figure below will give a better idea of what a niosome looks like and where the drug is located within the vesicle.

A typical niosome vesicle would consist of a vesicle forming ampiphile i.e. a



& NANOTECHNOLOGY

non-ionic surfactant such as Span-60, which is usually stabilized by the addition of cholesterol and a small amount of anionic surfactant such as diacetyl phosphate, which also helps in stabilizing the vesicle.

Method of Preparation of Niosomes

Niosomes can be prepared by a number of methods which are as follows:

Ether injection method:

In this method, a solution of the surfactant is made by dissolving it in diethyl ether. This solution is then introduced using an injection (14 gauge needle) into warm water or aqueous media containing the drug maintained at 60°C. Vaporization of the ether leads to the formation of single layered vesicles. The particle size of the niosomes formed depend on the conditions used, and can range anywhere between 50-1000µm.

Hand shaking method (Thin Film Hydration Technique):

In this method a mixture of the vesicle forming agents such as the surfactant and cholesterol are dissolved in a volatile organic solvent such as diethyl ether or chloroform in a round bottom flask. The organic solvent is removed at room temperature using a rotary evaporator, which leaves a thin film of solid mixture deposited on the walls of the flask. This dried surfactant film can then be rehydrated with the aqueous phase, with gentle agitation to yield multilamellar niosomes. The multilamellar vesicles thus formed can further be processed to yield unilamellar niosomes or smaller niosomes using sonication, microfluidization or membrane extrusion techniques.

Sonication

A typical method of production of the vesicles is by sonication of solution.In this method an aliquot of drug solution in buffer is added to the surfactant/cholesterol mixture in a 10-ml glass vial.

The mixture is probe sonicated at 60°C for 3 minutes using a sonicator with a titanium probe to yield niosomes.

Micro fluidization

Recent technique used to prepare unilamellar vesicles of defined size distribution. Based on submerged jet principle in which two fluidized streams interact at ultra high velocities, in precisely defined micro channels within the interaction chamber.



& NANOTECHNOLOGY

The impingement of thin liquid sheet along a common front is arranged such that the energy supplied to the system remains within the area of niosomes formation.The result is a greater uniformity, smaller size and better reproducibility of niosomes formed.

Multiple membrane extrusion method

Mixture of surfactant, cholesterol and dicetyl phosphate in chloroform is made into thin film by evaporation. The film is hydrated with aqueous drug solution and the resultant suspension extruded through polycarbonate membranes, which are placed in series for upto 8 passages. It is a good method for controlling niosome size.

Reverse phase evaporation technique:

This method involves the creation of a solution of cholesterol and surfactant (1:1 ratio) in a mixture of ether and chloroform. An aqueous phase containing the drug to be loaded is added to this, and the resulting two phases are sonicated at 4-5°C. A clear gel is formed which is further sonicated after the addition of phosphate buffered saline (PBS). After this the temperature is raised to 40°C and pressure is reduced to remove the organic phase. This results in a viscous niosome suspension which can be diluted with PBS and heated on a water bath at 60°C for 10 mins to yield niosomes.

Trans membrane pH gradient (inside acidic) Drug Uptake Process (remote loading):

In this method, a solution of surfactant and cholesterol is made in chloroform. The solvent is then evaporated under reduced pressure to get a thin film on the wall of the round bottom flask, similar to the hand shaking method. This film is then hydrated using citric acid solution (300mM, pH 4.0) by vortex mixing. The resulting multilamellar vesicles are then treated to three freeze thaw cycles and sonicated. To the niosomal suspension, aqueous solution containing 10mg/ml of drug is added and vortexed. The pH of the sample is then raised to 7.0-7.2 using 1M disodium phosphate (this causes the drug which is outside the vesicle to become non-ionic and can then cross the niosomal membrane, and once inside it is again ionized thus not allowing it to exit the vesicle). The mixture is later heated at 60°C for 10 minutes to give niosomes.

The “Bubble” Method:

It is a technique which has only recently been developed and which allows the preparation of niosomes without the use of organic solvents. The bubbling unit consists of a round bottom flask with three necks, and this is positioned in a water bath to control the temperature. Water-cooled reflux and thermometer is positioned in the first and second neck, while the third neck is used to supply nitrogen. Cholesterol and surfactant are dispersed together in a buffer (pH 7.4) at



& NANOTECHNOLOGY

70°C. This dispersion is mixed for a period of 15 seconds with high shear homogenizer and immediately afterwards, it is bubbled at 70°C using the nitrogen gas to yield niosomes.

Formation of Proniosomes and Niosomes from Proniosomes:

To create proniosomes, a water soluble carrier such as sorbitol is first coated with the surfactant. The coating is done by preparing a solution of the surfactant with cholesterol in a volatile organic solvent, which is sprayed onto the powder of sorbitol kept in a rotary evaporator. The evaporation of the organic solvent yields a thin coat on the sorbitol particles. The resulting coating is a dry formulation in which a water soluble particle is coated with a thin film of dry surfactant. This preparation is termed Proniosome.

The niosomes can be prepared from the proniosomes by adding the aqueous phase with the drug to the proniosomes with brief agitation at a temperature greater than the mean transition phase temperature of the surfactant.

Drugs incorporated into niosomes by various methods Method of preparation Drug incorporated

Ether Injection Sodium stibogluconateDoxorubicin

Hand Shaking MethotrexteDoxorubicin

Sonication 9-desglycinamide8-arginineVasopressin

Advantages of NiosomesUse of niosomes in cosmetics was first done by L’Oreal as they offered the following advantages:

The vesicle suspension being water based offers greater patient compliance over oil based systems

Since the structure of the niosome offers place to accommodate hydrophilic, lipophilic as well as ampiphilic drug moieties, they can be used for a variety of drugs.



& NANOTECHNOLOGY

The characteristics such as size, lamellarity etc. of the vesicle can be varied

depending on the requirement. The vesicles can act as a depot to release the drug slowly and offer a

controlled release.

Other advantages of niosomes are:

They are osmotically active and stable. They increase the stability of the entrapped drug Handling and storage of surfactants do not require any special conditions Can increase the oral bioavailability of drugs Can enhance the skin penetration of drugs They can be used for oral, parenteral as well topical use The surfactants are biodegradable, biocompatible, and non-immunogenic Improve the therapeutic performance of the drug by protecting it from the

biological environment and restricting effects to target cells, thereby reducing the clearance of the drug.

The niosomal dispersions in an aqueous phase can be emulsified in a non-aqueous phase to control the release rate of the drug and administer normal vesicles in external non-aqueous phase.

Comparison of Niosome v/s Liposome

Niosomes are different from liposomes in that they offer certain advantages over liposomes. Liposomes face problems such as –they are expensive, their ingredients like phospholipids are chemically unstable because of their predisposition to oxidative degradation, they require special storage and handling and purity of natural phospholipids is variable.

Niosomes do not have any of these problems. Also since niosomes are made of uncharged single-chain surfactant molecules as compared to the liposomes which are made from neutral or charged double chained phospholipids, the structure of niosomes is different from that of liposomes.

However Niosomes are similar to liposomes in functionality. Niosomes also increase the bioavailability of the drug and reduce the clearance like liposomes. Niosomes can also be used for targeted drug delivery, similar to liposomes. As with liposomes, the properties of the niosomes depend both- on the composition of the bilayer, and the method of production used.

CHARACTERIZATION OF NIOSOMES

a) Entrapment efficiency:

- Drug remained entrapped in niosomes is determined by complete vesicle disruption using 50% n-propanol or 0.1% Triton X-100 and analysing the resultant solution by appropriate assay method for the drug. Entrapment efficiency (EF) = (Amount entrapped/ total amount) x 100



& NANOTECHNOLOGY

b) Vesicle diameter: - Niosomes, similar to liposomes, assume spherical shape and so their diameter can be determined using,

light microscopy, photon correlation microscopy and freeze fracture electron microscopy.

Freeze thawing (keeping vesicles suspension at –20°C for 24 hrs and then heating to ambient temperature) of niosomes increases the vesicle diameter, which might be attributed to fusion of vesicles during the cycle. c) In-vitro studies: - A method of in-vitro release rate study includes the use of dialysis tubing. - A dialysis sac is washed and soaked in distilled water. The vesicle suspension is pipetted into a bag made up of the tubing and sealed. The bag containing the vesicles is placed in 200 ml of buffer solution in a 250 ml beaker with constant shaking at 25°C or 37°C. At various time intervals, the buffer is analyzed for the drug content by an appropriate assay method.

Applications of Niosomes

The application of niosomal technology is widely varied and can be used to treat a number of diseases. The following are a few uses of niosomes which are either proven or under research.

Drug Targetting:

One of the most useful aspects of niosomes is their ability to target drugs. Niosomes can be used to target drugs to the reticulo-endothelial system. The reticulo-endothelial system (RES) preferentially takes up niosome vesicles.The uptake of niosomes is controlled by circulating serum factors called opsonins. These opsonins mark the niosome for clearance. Such localization of drugs is utilized to treat tumors in animals known to metastasize to the liver and spleen. This localization of drugs can also be used for treating parasitic infections of the liver.Niosomes can also be utilized for targeting drugs to organs other than the RES. A carrier system (such as antibodies) can be attached to niosomes (as immunoglobulins bind readily to the lipid surface of the niosome) to target them to specific organs. Many cells also possess the intrinsic ability recognize and bind specific carbohydrate determinants, and this can be exploited by niosomes to direct carrier system to particular cells.

Anti-neoplastic Treatment:

Most antineoplastic drugs cause severe side effects. Niosomes can alter the metabolism, prolong circulation and half life of the drug, thus decreasing the side



& NANOTECHNOLOGY

effects of the drugs. Niosomal entrapment of Doxorubicin and Methotrexate (in two separate studies) showed beneficial effects over the unentrapped drugs, such as decreased rate of proliferation of the tumor and higher plasma levels accompanied by slower elimination.

Leishmaniasis:

Leishmaniasis is a disease in which a parasite of the genus Leishmania invades the cells of the liver and spleen. Commonly prescribed drugs for the treatment are derivatives of antimony (antimonials), which in higher concentrations can cause cardiac, liver and kidney damage. Use of niosomes in tests conducted showed that it was possible to administer higher levels of the drug without the triggering of the side effects, and thus allowed greater efficacy in treatment.

Delivery of Peptide Drugs:

Oral peptide drug delivery has long been faced with a challenge of bypassing the enzymes which would breakdown the peptide. Use of niosomes to successfully protect the peptides from gastrointestinal peptide breakdown is being investigated. In an invitro study conducted by Yoshida et al, oral delivery of a vasopressin derivative entrapped in niosomes showed that entrapment of the drug significantly increased the stability of the peptide.

Use in Studying Immune Response:

Due to their immunological selectivity, low toxicity and greater stability; niosomes are being used to study the nature of the immune response provoked by antigens.

Niosomes as Carriers for Haemoglobin:

Niosomes can be used as carriers for haemoglobin within the blood. The niosomal vesicle is permeable to oxygen and hence can act as a carrier for haemoglobin in anemic patients.

Transdermal Drug Delivery Systems Utilizing Niosomes:

One of the most useful aspects of niosomes is that they greatly enhance the uptake of drugs through the skin. Transdermal drug delivery utilizing niosomal technology is widely used in cosmetics, in fact, it was one of the first uses of the niosomes. Topical use of niosome entrapped antibiotics to treat acne is done. The penetration of the drugs through the skin is greatly increased as compared to un-entrapped drug. Recently, transdermal vaccines utilizing niosomal technology is also being researched. A study conducted by P. N. Gupta et al has shown that niosomes (along with liposomes and transfersomes) can be utilized for topical immunization using tetanus toxoid. However, the current technology in niosomes allows only a weak immune response, and thus more research needs to be done in this field.



& NANOTECHNOLOGY

Other Applications:

Niosomes can also be utilized for sustained drug release and localized drug action to greatly increase the safety and efficacy of many drugs. Toxic drugs which need higher doses can possibly be delivered safely using niosomal encapsulation.

Marketed Products:

Lancome has come out with a variety of anti-ageing products which are based on niosome formulations. L’Oreal is also conducting research on anti-ageing cosmetic products. A picture of the Lancome anti-ageing formulation is below.

Niosome Preparation

Sr.Sr. No.No.

Name of DrugName of Drug Objective Objective

11 Finasteride Finasteride

5-alpha reductase inhibitor 5-alpha reductase inhibitor

Orally in the treatment of alopecia. Targeted delivery ofOrally in the treatment of alopecia. Targeted delivery of Finasteride niosomes to hair follicles can increase theFinasteride niosomes to hair follicles can increase the concentration of the drug at pilosebaceous units withconcentration of the drug at pilosebaceous units with reducing its systemic side effects reducing its systemic side effects

2.2. Rifampicin Rifampicin

Anti-TB Anti-TB

Niosomes of rifampicin were prepared using Niosomes of rifampicin were prepared usingvarious nonionic surfactants of sorbitan ester class andvarious nonionic surfactants of sorbitan ester class and cholesterol in 50:50 percent mol fraction ratio. cholesterol in 50:50 percent mol fraction ratio.

The drug-entrapped vesicles were characterized forThe drug-entrapped vesicles were characterized for their shape, size, drug entrapment efficiency and in vitrotheir shape, size, drug entrapment efficiency and in vitro release rate.rifampicin encapsulated in niosomes couldrelease rate.rifampicin encapsulated in niosomes could successfully be used for treatment of tuberculosis alongsuccessfully be used for treatment of tuberculosis along lymphatic system. lymphatic system.

3.3. Methotrexate Methotrexate Efficacy of topical methotrexate in psoriasis isEfficacy of topical methotrexate in psoriasis is limited by its penetration. Niosomal methotrexate limited by its penetration. Niosomal methotrexate gel is more efficacious than placebo and marketed gel is more efficacious than placebo and marketed methotrexate gel. methotrexate gel.

4.4. Gentamicin Gentamicin

Aminoglycoside Aminoglycoside

AntibioticAntibiotic

Niosomal formulation of water soluble localNiosomal formulation of water soluble localantibiotic gentamicin sulphate was used for antibiotic gentamicin sulphate was used for Ophthalmic controlled delivery. Ophthalmic controlled delivery.

Formulations were prepared using various Formulations were prepared using various surfactants (Tween 60, Tween 80 or Brij 35), in thesurfactants (Tween 60, Tween 80 or Brij 35), in the presence of cholesterol and a negative charge inducerpresence of cholesterol and a negative charge inducer dicetyl phosphate (DCP) in different molar ratios and bydicetyl phosphate (DCP) in different molar ratios and by employing a thin film hydration technique employing a thin film hydration technique

5.5. PentoxifyllinePentoxifylline

Brochodilaror Brochodilaror

Pentoxifylline was entrapped in niosomes by lipid Pentoxifylline was entrapped in niosomes by lipid layer hydration method using Span 60, cholesterol layer hydration method using Span 60, cholesterol and dicetyl phosphate.The study indicates that and dicetyl phosphate.The study indicates that pentoxifylline may be an effective bronchodilator. pentoxifylline may be an effective bronchodilator.



& NANOTECHNOLOGY

Conclusion:

Over the years, there has been a great evolution in drug delivery technologies. Niosomal drug delivery systems are an example of one of the various drug delivery systems available. The technology utilized in niosomes is still greatly in its infancy, and already it is showing promise in the fields of cancer and infectious disease treatments. The system is already in use for various cosmetic products. Niosomes represent a promising drug delivery technology and much research has to be inspired in this to juice out all the potential in this novel drug delivery system.

NanotechnologyCONTENTS

1.Nanotechnology2.Nanoparticles3.Types of Nanoparticulate Systems4.Nanoparticulate Formulation

4.1 Materials4.2 Preparation of NPs4.3 Surface Modification of NPs4.4 Drug Loading into NPs

5.Characterization & Evaluation of NPs6.Distribution and Fate of Colloidal Drug Carriers7.Therapeutic Applications of Colloidal Drug Carriers8.Nanotechnologies for Drug Delivery9.Chemical Abstracts10.Obstacles to Industrial Developments11.Concluding Remarks 12.Commercial Products

1.NANOTECHNOLOGY



& NANOTECHNOLOGY

Nanotechnology received a lot of attention with the never-seen-before

enthusiasm because of its future potential that can literally revolutionize each field in which it is being exploited. In drug delivery, nanotechnology is just beginning to make an impact.

Many of the current “nano” drug delivery systems, however, are remnants of conventional drug delivery systems that happen to be in the nanometer range, such as liposomes, polymeric micelles, nanoparticles, dendrimers, and nanocrystals.

Liposomes and polymer micelles were first prepared in 1960’s, and nanoparticles and dendrimers in 1970’s. Colloidal gold particles in nanometer sizes were first prepared by Michael Faraday more than 150 years ago, but were never referred to or associated with nanoparticles or nanotechnology until recently. About three decades ago, colloidal gold particles were conjugated with antibody for target specific staining, known as immunogold staining.

Such an application may be considered as a precursor of recent explosive applications of gold particles in nanotechnology.

The importance of nanotechnology in drug delivery is in the concept and ability to manipulate molecules and supramolecular structures for producing devices with programmed functions. Conventional liposomes, polymeric micelles, and nanoparticles are now called “nanovehicles,” and this, strictly speaking, is correct only in the size scale. Those conventional drug delivery systems would have evolved to the present state regardless of the current nanotechnology revolution.

To appreciate the true meaning of nanotechnology in drug delivery, it may be beneficial to classify drug delivery systems based on the time period representing before and after the nanotechnology revolution.

Examples of drug delivery technologies in relation to the current nanotechnology revolution.

Period Before Nanotechnology (Past)

Transition Period (Present)

Mature Nanotechnology (Future)

Technology Emulsion-based preparation of nano/micro particles

Nano/micro fabrication Nano/micro manufacturing

Examples - Liposomes - Polymer micelles - Dendrimers - Nanoparticles - Nanocrystals - Microparticles

- Microchip systems - Microneedle

transdermal delivery systems

- Layer-by-layer assembled systems

- Microdispensed particles

- Nano/micro machines for scale-up production

Schematic comparison of targeted and untargeted DDS



& NANOTECHNOLOGY

2.NANOPARTICLES

Nanoparticles are solid colloidal particles consisting of macromolecular substances that vary in size from 10nm to 1,000nm.The drug of interest is dissolved, entrapped, adsorbed attached or encapsulated into the nanoparticle matrix.Depending upon the method of preparation, nanoparticles, nanospheres or nanocapsules can be obtained with different properties and release characteristics for the encapsulated therapeutic agent.


NANOPARTICLES


& NANOTECHNOLOGY

3.TYPES OF NANOPARTICULATE SYSTEMS


(Matrix systems) (Reservior systems)

NA

NO

SP

HER

ES

NA

NO

CA

PS

ULES


& NANOTECHNOLOGY

Sr. No.

Types of Nanoparticles

Material Used Applications

1. Polymeric nanoparticles

Biodegradable polymers

Controlled and targeted drug delivery

2. Solid lipid nanoparticles

Melted lipid dispersed in an aqueous surfactant

Least toxic and more stable colloidal carrier systems as alternative to polymers

3. Nanocrystals & nanosuspensions

Drug powder is dispersed in a surfactant solution

Stable systems for controlled delivery of poorly water soluble drugs

4. Polymeric micelles Amphiphilic block copolymers

Systemic and controlled delivery of water insoluble drugs

5. Liposomes Phospholipid vesicles Controlled and targeted drug delivery

6. Dendrimers Tree like molecules with defined cavities

Drug targeting

7. Magnetic NPs An inorganic core of iron oxide (magnetite) coated with polymer such as dextran

Drug targeting, Diagnostic tool in biology and medicine

8. Gold nanoshells Dielectric (typically gold sulfide or silica) core

Tumor targeting


12

3

4

56

7

8

9

10

Types of Nanoparticulate

systems


& NANOTECHNOLOGY

and a metal (gold) shell

9. Nanowires or Carbon nanotubes

Metals, semiconductors or carbon

Gene and DNA delivery

10. Ferrofluids Iron oxide magnetic NPs surrounded by a polymeric layer

For capturing cells and other biological targets from blood or other fluids and tissue samples

4.NANOPARTICULATE FORMULATION 4.1Materials

4.2Preparation of NPs4.3 Surface Modification of NPs4.4 Drug Loading into NPs

4.1 Materials

4.1.1 Polymers

Methods of NPs preparation Polymers

Monomers polymerization Poly(alkyl cyanoacrylate) Poly(alkyl methacrylate)Poly(styrene)Poly(vinylpyridine)

Nanoprecipitation Poly(ε-caprolactone) Poly(lactic acid)Poly(lactic-co-glycolic acid)Poly(methacrylate)

Solvent evaporation Poly(ε-caprolactone) Poly(lactic acid)Poly(lactic-co-glycolic acid)Poly(β-hydroxybutyrate)Ethyl cellulose

Salting out Cellulose acetate phthalatePoly(alkyl methacrylate)Ethyl cellulosePoly(lactic acid)Poly(lactic-co-glycolic acid)



& NANOTECHNOLOGY

Desolvation, denaturation, ionic gelation

Albumin CaseinGelatinAlginateChitosanEthyl cellulose

4.1.2 StabilizersGenerally surfactants are used as stabilizers to reduce high surface free

energy of nanosized particles.Generally used stabilizers are-

Cellulosic Poloxamers 184, 188, 338, 407 Poloxamine 908 Polysorbates 20, 40, 60, 80 Lecithins Cremophor EZ and RS 40 Polyoxyethylene lauryl ether Povidones Lecithin is stabilizer of choice for parenteral preparations.

4.1.3 Organic solventsWater immiscible organic solvent : Methylene chloride Chloroform DCM

Partially water miscible solvent : Ethyl acetate Ethyl formate

Butyl lactate Triacetin Propylene carbonate Benzyl alcohol

Water miscible solvent : Ethanol Isopropanol

4.1.4 Co-surfactants Bile salts

Dipotassium Glycerrhizinate Transcutol Glycofurol Ethanol IPA

4.1.5 Other additives



& NANOTECHNOLOGY

Includes BuffersSalts PolyolsOsmogentsCryoprotectants

4.2 Preparation of NPs

4.2.1 Solvent evaporation

Polymer is dissolved in organic solvent like acetone, chloroform etc. The drug is dissolved or dispersed into the preformed polymer solution. Then the mixture is emulsified with aqueous phase to prepare o/w emulsion

by using a surfactant. After formation of a stable emulsion, the organic solvent is evaporated either

by increasing temperature/under reduced pressure or by continuous stirring. The w/o/w method is also applied to prepare water soluble drug loaded NPs. Both the above method uses a high speed homogenization or Sonication.

4.2.2 Spontaneous emulsification/Solvent diffusion method

It is a modified version of solvent evaporation method. Here water soluble solvent like acetone along with water insoluble solvent

like chloroform are used as an oil phase. Due to spontaneous diffusion of water soluble solvent, an interfacial

turbulence is created between two phases that leads to formation of smaller particles.

As the concentration of water soluble solvent increases, a considerable decrease in particle size can be achieved.

4.2.3 Salting out

Drug and polymer are first dissolved in solvent and then they are subjected to homogenization with aqueous solvent having salting out agent and at last salts are removed by cross-flow filtration.

4.2.4 Monomer polymerization

Here we will see NPs formation using poly(alkyl cyano acrylate). The cyanoacrylic polymer is added to an aqueous acidic solution of surface

active agent (polymerization medium) under vigorous mechanical stirring. Drug is dissolved in the polymerization media either before the addition of

monomer or at the end of polymerization reaction. The NP suspension is then purified by ultracentrifugation or by resuspending

the particles in an isotonic surfactant free medium.



& NANOTECHNOLOGY

Particle size and molecular mass of NP depend upon the type & conc. of

surfactant, pH of the medium, conc. of monomer and stirring speed.

4.2.4 NPs prepared from hydrophilic polymersi) Denaturation

It involves emulsification of an aqueous solution containing a natural polymer and the drug to be entrapped in an oil emulsion.

The particles are hardened by heat Denaturation, cooling below the gelation point or by cross-linking with suitable agent.

ii) Desolvation Commonly known as coacervation (similar to microspheres)

iii) Ionic gelation Ion induced gelation results into formation of NPs.

4.2.6 Supercritical fluid technologyi) Rapid expansion of super critical solution (RESS)

The solute of interest is first dissolved in SCF. Then the solution is expanded through a nozzle. Thus the solvent power of SCF decreases and so the solute precipitates. This technique is clean because the precipitated solute is completely solvent

free. Unfortunately, most polymers exhibit little or no solubility inSCF, thus making

the technique less of practical interest.

ii) Supercritical anti-solvent (SAS) Both the solution of solute in a suitable solvent and SCF are charged in the

precipitation vessel. Because of high pressure, enough antisolvent will enter into the liquid phase,

so the solvent power will be reduced and solute precipitates.

iii) Gas anti-solvent technique (GAS) It is a modified version of SAS method. The solution of solute is rapidly introduced into the SCF through a narrow

nozzle. The SCF completely extracts the solvent, causing precipitation of solute.

4.3 Surface Modification of NPs Following two methods are useful for surface modification:i) Surface coating with hydrophilic polymers/surfactants

PEG PEO Poloxamer Poloxamine Polysorbate Lauryl ethers (Brij-35)

ii) Development of biodegradable co-polymers with hydrophilic segments (PLA-PEG, PLGA-PEG)



& NANOTECHNOLOGY

These modification lead to change in zeta potential and hydrophobicity of NPs

that ultimately affects following properties:o Stabilityo Mucoadhesive propertieso Oral absorptiono Protein adsorption at surface

4.4 Drug Loading into NPsFollowing methods are used for drug loading into NPs:

i) Entrapment method It involves the incorporation of the drug at the time of NP

production. It depends on the concentration of monomers. Large amount of drug can be entrapped by this method as

compared to adsorption method. ii) Adsorption method

Here, the drug is loaded by incubating the pre-formed NPs in the drug solution.

The capacity of adsorption depends on the hydrophobicity of the polymer and the specific surface area of NPs.

iii) Chemical conjugation New method for drug loading of water soluble drugs. In one article, they have utilized this method to prepare

conjugated doxorubicin-PLGA NPs. These NPs showed higher loading capacity as compared to unconjugated doxorubicin-PLGA NPs.

5. CHARACTERIZATION & EVALUATION OF NPs

5.1 Physicochemical Characterization5.2 Drug Release from NPs

5.1 Physicochemical Characterization

Parameter MethodsParticle size Photon correlation spectroscopy

Transmission electron microscopy Scanning electron microscopy Scanned-probe microscopy Fraunhofer diffraction LASER diffractometry Coulter counter



& NANOTECHNOLOGY

Molecular Weight Gel permeation chromatography

Density Helium compression pyncnometry

Crystallinity X-ray diffractionDSCDTA

Surface charge ElectrophoresisLaser Doppler anemometry Amplitude-weighted phase structure determination

Hydrophobicity Hydrophobic interaction chromatographyContact angle measurement

Surface properties Static secondary-ion mass spectrometry

Surface element analysis X-ray photoelectron spectroscopy for chemical analysis

5.2 Drug Release from NPs

Methods to study in vitro release are as follow:1. Side- by- side diffusion cells with artificial or biological membrane2. Dialysis bag diffusion technique3. Reverse dialysis sac technique4. Ultracentrifugation 5. Ultrafiltration6. Centrifugal ultrafiltration

Mechanisms of drug release from NPs are as follow:

6.DISTRIBUTION & FATE OF COLLOIDAL DRUG CARRIERS



& NANOTECHNOLOGY

After intravenous administration, these particles cannot extravasate except in tissues with a discontinuous capillary endothelium; that is, the liver, spleen and bone marrow. Even in these organs, the size of the gaps between endothelial cells (approximately 100 nm) means that only the smallest particles can penetrate into the tissue.

Carriers may extravasate into solid tumours and into inflamed or infected sites, where the capillary endothelium is defective.

However, for ‘conventional’ colloidal carriers, which have more or less hydrophobic surfaces, the usual fate is opsonization by plasma proteins, followed by uptake by phagocytic cells: either polymorphonuclear leukocytes in the blood or fixed macrophages, particularly the Küpffer cells in the liver.

Complement activation by the alternative pathway is an important component of carrier recognition and uptake, but opsonization by other plasma proteins, for example nonspecific adsorption of IgG, also intervenes.

When colloidal drug carriers are administered by other routes, such as by subcutaneous or intramuscular injection or topical application, they are generally retained at the site of administration for longer than free drug. When a liposome associated drug is applied to the skin, the amount penetrating into the superficial layers may be increased compare with free drug, while its passage to the systemic circulation may be reduced. After subcutaneous or intraperitoneal administration, small liposomes and nanoparticles have been shown to be taken up by regional lymph nodes.

The most convenient route of drug administration is the oral method. However, this route presents several barriers to the use of colloidal carriers, because the environment within the gastrointestinal (GI) tract can disrupt many of them. It has been shown that the concerted action of duodenal enzymes and bile salts destroys the lipid bilayers of most types of liposomes, thus releasing the drug. Multilamellar liposomes prepared from phospholipids whose phase transition temperatures are above 37 o C and which contain cholesterol in their bilayers are the most resistant to degradation. Polymeric nanoparticles are more stable, although there is some evidence that polyesters can be degraded by pancreatic lipases.


Drug release from NPs

Desorption

Combined erosion

/diffusion

Erosion of NP matrix

Diffusion through

polymer wall

Diffusion through NP

matrix


& NANOTECHNOLOGY

Even if the carrier is stable, anatomical considerations mean that only a small

proportion of the administered drug-carrier systems can be absorbed intact across the intestinal mucosa into the circulation or the lymphatics.

Passage across enterocytes by diffusion is restricted to small, lipophilic molecules and transcytosis, which is rare, to particles of less than 200 nm in diameter. Passage by the paracellular pathway is impossible if the tight junctions are intact. Nevertheless, several studies have reported the appearance of particles in the circulation after oral dosing. The current consensus is that uptake occurs via Peyer’s patches, which are specialized areas of the gut-associated immune system. Transcytosis of particles occurs across M cells and delivers them to the underlying lymphoid follicule.

7. THERAPEUTIC APPLICATIONS OF COLLOIDAL DRUG CARRIERS

Conventional drug carriers:- i) Intravenous route

Since colloidal drug carriers are naturally concentrated within macrophages, it is logical to use them to deliver drugs to these cells.

A good example is the delivery of muramyldipeptide and chemically related compounds to stimulate the antimicrobial and antitumoral activity of macrophages.

Muramyldipeptide is a low molecular-weight, soluble synthetic compound derived from the peptidoglycan of mycobacteria, and, although it acts on intracellular receptors, it penetrates poorly into macrophages. Furthermore, muramyldipeptide is eliminated rapidly after intravenous administration. These problems can be overcome by encapsulation within liposomes or nanocapsules.

Macrophages may also be sites for bacterial and parasitic infections. Liposomes or nanoparticles can be used to concentrate antibiotics at the site

of infection, particularly when the microorganism is within the lysosomes. For example, nanoparticles containing ampicillin were more effective than the free drug against both Salmonella typhimurium and Listeria monocytogenes.

The potential of liposomes as immunological adjuvants was recognized in 1974. In the case of protein antigens, encapsulation increases capture by antigen-presenting cells such as macrophages. In an alternative strategy, immunogenic peptides have been coupled to the surface in order to directly activate B and T cell clones. Liposomes have also been used as carriers in DNA vaccines.

Colloidal carriers can also be useful for diverting drugs from sites of toxicity after intravenous administration. For example, the anticancer drug doxorubicin (adriamycin) is active against a wide spectrum of tumours, but has dose-limiting cardiotoxicity. Encapsulation within liposomes or nanoparticles decreases this toxicity, by reducing the amount of drug that reaches the myocardium.



& NANOTECHNOLOGY

A corollary is that concentrations of doxorubicin in the liver increase

considerably. In one study in mice, this was not associated with any gross toxicity. However, another group reported a temporary depletion of Küpffer cells, and hence the ability to clear bacteria, in rats, which was less marked when long-circulating liposomes were used.

Thus, altered distribution may generate new types of toxicity and this must be considered when developing carrier systems.

ii) Oral route

iii) Other routes

Colloidal drug carrier systems have been used to concentrate gamma-interferon in the skin for the treatment of cutaneous herpes. The cytokine accumulated in the stratum corneum, rather than remaining on the surface as occurred after administration of a simple solution.

The application of carrier formulations to the eye retards elimination of drug from the corneal surface. This has been demonstrated for beta-blockers and cyclosporin A within nanospheres and nanocapsules.

Subcutaneous or intra-peritoneal administration of anticancer agents in liposomes has been shown to deliver the drug to lymphatic metastases. The use of nanocapsules has also been shown to reduce drug-related irritation.

Second generation drug carriers:-

i) Systems avoiding uptake by phagocytic cells

Despite the promising results achieved with some ‘first-generation’ drug carrier systems, their value is limited by their distribution and, in particular, by their recognition by the mononuclear phagocyte system.

Early work had showed that small liposomes and those containing some negatively charged lipids (ganglioside GM1 or hydrogenated phosphatidylinositol) remained in the bloodstream for longer.

Increased circulation time could also be achieved to some extent by administration of high doses, which saturated the phagocytic system.


Protection of drug from degradation in GIT (e.g.,

Insulin)

Protection of GIT from drug toxicity (e.g., NSAIDs)

Improved absorption of poorly water soluble drugs

Delivering antigens to the peyer's patches for oral

immunization


& NANOTECHNOLOGY

The major breakthrough, however, was the use of phospholipids substituted

with poly (ethylene glycol) chains of molecular weight from 1000–5000, as 5–10% of the total lipid.

A doxorubicin-containing formulation based on ‘Stealth™’ liposomes (Alza Corporation, Mountain View, CA, USA), Doxil™ (Alza Corp.), is commercially available for use in AIDS-related Kaposi’s sarcoma. Although not containing PEG-substituted lipids, DaunoXome™ (Gilead Sciences, Foster City, CA, USA) can be considered as a long-circulating formulation because of the small size of the liposomes (50 nm).

As well as accumulating in solid tumours, long-circulating colloidal carriers can extravasate into sites of inflammation and infection.

Another strategy for preparing long-circulating colloidal systems can be considered as biomimetic, in that it seeks to imitate cells or pathogens that avoid phagocytosis by reducing or inhibiting complement activation. One example is the development of liposomes with a membrane composition similar to that of erythrocytes; for example, liposomes containing GM1 or those coated with polysialic acids.

ii) Systems avoiding lyososomal compartment

Hydrophilic molecules (such as nucleic acids) require intracellular delivery, but they are finding difficulties in crossing plasma membrane. Also if the carrier is taken up by endocytosis, its ultimate destination will be the lyososomes in which the hydrolytic enzymes will degrade both the carrier and its contents. To eliminate such problems & effectively deliver such molecules fusogenic technology is discovered. Liposomes fusing directly with the plasma membrane with the help of fusogenic proteins or peptides. This is particularly important in case of delivering genes & antisense oligonucleotides.

iii) Systems targeted to specific cell populations

An ideal drug carrier system would contain a specific ‘homing group’ capable of being recognized by the target cells.

Much work has been devoted to coupling specific ligands to the surface of liposomes. Monoclonal antibodies or fragments thereof have often been used because of their specificity.

Other targeting systems that have been investigated are sugar–lectin interactions, such as the mannose or fucose receptor of macrophages and the galactose receptor of hepatocytes, hormone and growth-factor receptors and receptors for cell nutrients such as transferrin and folic acid, which are over-expressed in some tumours.

In short, nanotechnology is an intelligent design (due to its above mentioned properties) which is useful to overcome the following



& NANOTECHNOLOGY

therapeutic challenges that are faced during treatment of certain complex diseases.

New nanotech anti-cancer drug delivery system introduced

A new anti-cancer drug delivery system which allows more targeted treatment and helps avoid the unsafe and unpleasant side effects of chemotherapy is due to enter clinical trials in Europe and the US for use with anti-cancer drug paclitaxel.


Therapeutic challenges

CancerIncrease efficacyReduce toxicityInfectionsIncrease efficacyReduce toxicityMetabolic diseasesProtection against degradationImprove mucosal absorptionControlled releaseAuto-immune diseasesGene therapy related diseases

Control biodistribution to target immune systemControlled release

Protection against degradationCondense DNAImprove cellular uptakeAddress cytoplasmic/nucleus compartments


& NANOTECHNOLOGY

8. NANOTECHNOLOGIES FOR DRUG DELIVERY



& NANOTECHNOLOGY

New nanotech anti-cancer drug delivery system introduced

A new anti-cancer drug delivery system which allows more targeted treatment and helps avoid the unsafe and unpleasant side effects of chemotherapy is due to enter clinical trials in Europe and the US for use with anti-cancer drug paclitaxel.

"Owing to its water insolubility, the widely used chemotherapy agent paclitaxel that is known to have substantial anti-tumour activity is now used with a castor oil based solvent, cremophor, which in turn is an agent for life threatening side effects," said Dabur Research Foundation R&D president Dr Rama Mukherjee.

"The anti-cancer drug nanoxel, based on principles of nanotechnology, is a cremophor free soluble formulation - and is indicated as an effective and safe therapy for advanced breast, non-small-cell lung, and ovarian carcinomas."

9. CHEMICAL ABSTRACTS

146:148535g Chitosan nanoparticles for oral drug and gene delivery

• Chitosan is mucoadhesive polymer and increases cellular permeability and bioavailability of orally administered protein drugs.

• It readily forms NPs that are able to entrap drugs or condense plasmid DNA.



& NANOTECHNOLOGY

146:343883w Poly (propyleneimine) dendrimer based nanocontainers for targeting of efavirenz to human monocytes/macrophages in vitro

• Efavirenz is useful in the treatment of HIV infection.• Cells of the mononuclear phagocyte system, in particular

monocytes/macrophages serve as a reservior for HIV and are believed to be responsible for its spread throughout the body and especially into brain.

146:343936r Preparation, characterization and in vitro cytotoxicity of paclitaxel-loaded sterically stabilized SLNs

• The SLNs, comprising trimyristin as a solid lipid core and egg phosphatidyl choline & PEGylated phospholid as stabilizers, were prepared using hot homogenization method.

• The prepared SLNs provided slow and sustained release.

147:79245u Penetration of metallic NPs in human full thickness skin • According to theories of TDDS, structure & complexation do not

allow the penetration of materials larger than 600 Da, yet some articles on particle penetration into the skin have been recently published.

• The aim is to evaluate whether metallic NPs smaller than 10 nm could penetrate and eventually penetrate the skin.

147:79063h Solubility enhancement of poorly water soluble molecules using dendrimers

• Poor water solubility results into poor bioavailability.• Model drugs- Cisplatin & indomethacin • Dendrimer-drug formulations showed upto 37-fold drug solubility

enhancement.

147:150372r Long-circulating NPs via adhesion on RBCs: Mechanism and extended circulation

• The authors reported that attaching polymeric NPs to the surface of RBCs improves their in vivo circulation life time.

• Particles eventually detach from RBCs due to shear forces and cell-cell interactions and are subsequently cleared in the liver and spleen.

• Circulation of RBCs themselves is not affected by particle attachment procedures.

10. OBSTACLES TO INDUSTRIAL DEVELOPMENTS

Cost The problem of cost results in funding research. Today, most developments

are carried on by small entrepreneurial firms including many spin-ups that



& NANOTECHNOLOGY

cannot support themselves as yet on current revenues, whereas big pharmaceutical companies seem still awaiting for more successes.

Fortunately, governments are strongly convinced by the potential economic impacts that nanotechnology can raise in the medical field by reducing hospitalization and medical care cost. Thus, all big countries open large funding programs to support the cost of research. They encourage the building of strong partnerships at the national and international level among academic and industrial partners with multidisciplinary expertise . This allows the small entrepreneurial firms to find valuable financial complement to their venture capital from government grants.

The problem of cost is also somehow linked to the management of the intellectual property rights. For the survival of a company, it is economically essential to build a relevant intellectual property strategy taking patents that will protect the technology and the commercial interests on both an offensive and a defensive stand point . The nanosystems designed for the delivery of drugs are part of the nanotechnology that is subjected to the intellectual property rights.

The issue is believed to have a huge impact in the future of the drug delivery sciences that companies are generally very cautious about these aspects.

Universities and government institutions also hold several patents and promote transfer technology to company.

Regulatory approval It is only recently that the FDA adopted a clear position about regulations that

may apply to product coming out from nanotechnology. FDA has identified a couple of regulated products that are expected to be

impacted by nanotechnology including drugs (new molecular entities or novel delivery systems), medical devices, biotechnology products, tissue engineering products, vaccines, cosmetics, and combination products .

Among these, applications in pharmacology include drugs, vaccines, and combination products.

The general concerns of FDA on nanotechnology products are about safety, quality, and characterization of material and environmental impact.

However, it seems that there are currently no testing requirements that are specific to nanotechnology products. If research identifies toxicological risks that are unique to nanomaterials, additional testing requirements may become necessary.

At the moment, the FDA is not anticipating any new guidance documents regarding nanomaterials in the near future. It indicates that the process of approval for nanomaterials will be the same as that used for other products making the same claims.

It would not be surprising if the present regulation will change in the near future because a large debate was recently opened to evaluate the real benefits to risk of the enlargement of nanotechnology for applications and to identify possible hazards.

General fears



& NANOTECHNOLOGY

As a general skepticism, people are aware that chemical properties may

become toxic at the nano level. In the case of pharmacology and especially as far as treatment of cancer is concerned, it has to be taken into account that toxicity is useful owing it is targeted.

Focusing on pharmacological applications, fears include the feeling that engineering delivery systems will increase time and cost. It is true that research programs on these systems cost a huge amount of money mainly because a lot remains to be discovered to improve and to extend their uses.

Finally, application of nanotechnology often requires development of partnerships with experts outside the company. Many drug discovery companies are afraid to share information that they consider as highly risky with a third party. For a successful collaboration, the management of the intellectual properties must be considered very carefully at the beginning of the business relationship, defining clear intellectual properties ownerships in a contract that could help overcome this reluctance

11. COMMERCIAL PRODUCTS

REFERENCES



& NANOTECHNOLOGY

Gert Storm, et al., Liposomes: Quo vadis?, Pharm. Sci. Tech. Today 1 (1998) 19-31D.J.A. Crommelin, et al., Liposomes: vesicles for the targeted and controlled delivery of peptides and proteins, J. Control. Release 46 (1997) 165-175Andreas Wagner, et al., Liposomes produced in a pilot scale: Producton, Purification and efficiency aspects, Eur. J. Pharm. Biopharm. 54 (2002) 213-219Sugi S. Chrai, et al., Liposomes, part II: drug delivery systems, Pharm. Technol. Europe (February 2003) 53-56Jessy Shaji, et al., Immunoliposomes: targeted delivery for cancer, Pharma Times 39 (2007) 17-20Gregoriaadis G, Liposomes in drug delivery: clinical, diagnosticand ophthalmic potential, Drugs 45 (1993) 15-28

Jorg Kreuter, Nanoparticles-a historical perspective, Int. J. Pharm. 331 (2007) 1-10

Jain S, et al., Nanoparticles: Emerging carriers for delivery of bioactive agents, Pharma Times 39 (2006) 30-35

S. M. Moghimi, Particulate nanomedicines, Adv. Drug Deliv. Rev. 58 (2006) 1451-1455

Anne des Rieux, et al., Nanoparticles as potential oral delivery systems of proteins and vaccines: a mechanistic approach, J. Control. Release 116 (2006) 1-27


liposomes, niosomes and nanotechnology

Documents