ocular drug delivery system

OCULAR DRUG DELIVERY SYSTEM

Dr. Muhammad Harris Shoaib

� LIMITATION OF CONEVENTIONAL SYSTEM� TOPICAL

� Complex ocular physiological and cellular barrier

� Cornea, a major barrier to absorption

� Instilled dose lost by protective mechanism such as � Instilled dose lost by protective mechanism such as � Solution drainage

� Lacrimation

� Systemic absorption via conjuctiva (Not required for topical)

� SYSTEMIC� Poor access to the internal structure within the globe

� Blood Ocular barrier

� OBJECTIVES FOR ADVANCED OCULAR DRUG DELIVERY SYSTEM

� To find newer, effective, predictable and safe drug molecules for various ocular conditions and disease they are poorly controlled nowthey are poorly controlled now

� To improve the ocular dosage form and delivery system by which existing drugs are administered

� ANATOMY AND PHYSIOLOGY OF EYE� Eye is an isolated and highly specialized organ of photoreception

� Made up of three layers�Outer fibrous protective sclera�Outer fibrous protective sclera

�Middle vascular uvea including choroid, the ciliary body and the iris

� Inner neural retina

� Eye overall divided into two segment� Anterior Segment

� Posterior Segment

� ANTERIOR SEGMENT� The Cornea

� The anterior segment of the eye is bound anteriorly by a transparent cornea and a small portion of the sclera.

� The junction where the cornea and the sclera join is called the limbuslimbus

� The human cornea is approximately 0.5 mm thick in the center, with the periphery being thicker than the central part.

� It is a transparent avascular structure that receives its nourishment and oxygen supply from aqueous humor and the tear film

� The tissue is composed of five layers: the epithelium, bowman’s membrane, stroma, descemets membrane, and the endothelium

� Epithelium

� Outer protective layer

� 5-6 layers of superficial squamos and basal columnar epithelial cells

� Numerous microvilli protrude into the lacrimal film from these cells.

The microvilli are covered by mucin and glycocalix. � The microvilli are covered by mucin and glycocalix.

� The superficial epithelial cell layers have tight junctionalcomplexes between adjacent cells called zonulaeoccludentes.

� These junctional complexes prevent the passage of water-soluble drugs with low lipophilicity across the cornea.

� The corneal epithelium is a reasonably hydrophobic tissue

� Drugs to cross the cornea it should have an oil–water partition coefficient greater than 1.

� Bowman’s Membrane� Bowman’s membrane is an acellular thin layer made of collagen fibrils.

� Anteriorly it is separated from the epithelium by a basement membrane.

� It does not offer high diffusional resistance and as such it is not a rate limiting barrier

Stroma� Stroma� This corneal layer is a highly organized structure constituting 90% of the cornea.

� It consists of parallel collagenous lamellae. � Between the lamellae lies the modified fibroblast known as keratocytes.

� The stromal layer becomes a limiting barrier for permeation� of lipophilic drug� Minimal resistance to hydrophilic drugs

� Descemets Membrane

� Descemets membrane is a thin homogeneous layer between the stroma and the endothelium.

� Endothelium

� The corneal endothelium is a single-layered squamousepithelium on the posterior surface of the cornea. epithelium on the posterior surface of the cornea.

� The endothelial cells do not posses tight junctions.

� This layer does not act as a barrier to drug molecules.

� Plays an important role in regulation of corneal hydration by transferring bicarbonate and chloride into the aqueous humor.

� Conjunctiva� The conjunctiva is a vascularized mucous membrane that covers the inner surface of the eyelids and the anterior part of the sclera.

� It offers less resistance to the passage of drug molecules than the cornea.

� Iris� The iris is the most anterior portion of the uveal tract.

� The iris consists of the pigmented epithelial cell layer, the iridic sphincter � The iris consists of the pigmented epithelial cell layer, the iridic sphincter and dilator muscles, and the stroma

� The anterior surface of the irisis the stroma, which contains melanocytes, blood vessels, smooth muscle, parasympathetic and sympathetic innervations.

� Individual eye color varies according to the number of melanocytespresent in the stroma.

� Ocular pigmentation may be an important factor relative to ocular bioavailability owing to drug–melanin binding.

� The iris has high enzymatic activity, resulting in low ocular bioavailability.

� Ciliary Body� Composed of the ciliary muscle and the ciliary processes� Ciliary muscle plays an important role in accommodation� Ciliary processes are the highly vascularized folds protruding into the posterior chamber.

� These are covered by a two-layered epithelium, the inner nonpigmented and the outer pigmented epithelium. nonpigmented and the outer pigmented epithelium.

� The nonpigmented epithelial cells are attached to each other by junctional complexes, which obstruct the diffusion of large molecules into the aqueous humor.

� Aqueous Flow Pathway� Aqueous humor is secreted by the ciliary processes into the posterior chamber at the rate of 2 to 2.5 µl/min.

� Aqueous humor flows continuously from the posterior chamber to the anterior chamber through the pupil and from there it leaves the eye through the trabecular meshwork and Schlemm’s canal.

� Plays an important role in the nourishment and supply of oxygen to the avascular tissues in the eye.

� It also carries metabolites away from the surrounding tissues.

� Continuous flow of aqueous humor is important for maintaining the constant volume and intraocular pressure.

� Lens� Lens

� crystalline structure surrounded by the lens capsule.

� It is located behind the iris and in front of the vitreous.

� The lens is important for the visual function and together with the ciliary muscle it enables accommodation and protects the retina from harmful ultraviolet radiation.

� Lacrimal Apparatus

� Tear fluid is secreted by the main lacrimal gland, the acessoryglands, and the meibomian glands.

� The normal tear flow rate is approximately 1 µl/min, and it covers the cornea and the conjunctiva.

The tear fluid has a nutrition function as well as an � The tear fluid has a nutrition function as well as an antibacterial function.

� Tear fluid secretion also helps in lubricating the eye and washing away debris.

� It is drained through the canaliculi, lacrimal sac, nasolacrimalduct, and finally into the nasal cavity.

� POSTERIOR SEGMENT

� Retina

� The retina is a thin, transparent neural tissue extending anteriorly to the pars plana of the ciliary body

� It is the innermost tissue� It is the innermost tissue

� Consisting of neural layer and the pigmented epithelium

� The pigmented epithelial cells are connected with tight junctions and forms a barrier the vascular choroid and retina

� Vitreous Humor

� Vitreous is a clear medium that fills the cavity between the retina and the lens.

� It is composed of 98 to 99.7% water.

� The vitreous mainly consists of dissolved collagen, hyaluronicacid, and proteoglycans. acid, and proteoglycans.

� It is easily susceptible to bacterial infection, and the treatment of vitreal infections becomes challenging owing to poor bioavailability of the antibiotics.

� The blood retinal barrier largely prevents the entry of many drugs into the vitreous from the systemic circulation..

� The Choroid and the Sclera� The choroid is a highly vascularized tissue between the retina and the sclera.

� It constitutes the posterior part of the uvea that represents the middle vascular coat of the eye.

� The primary function of the choroid is to nourish the outer � The primary function of the choroid is to nourish the outer layers of the retina.

� The sclera is the outermost layer, consisting of collagen bundles and elastic fibers.

� The sclera functions to both protect the intraocular contents and to maintain the shape of the eye.

� It is permeable to molecules as large as dextran; hence the transscleral route can be used to deliver drugs to the posterior segment.

� ROUTES OF OCULAR DRUG DELIVERY�Topical administration

� The topical route of administration is used to treat diseases that affect the anterior segment of the eye such as keratitis, conjunctivitis, and glaucoma. They may not provide the desired therapeutic concentration � They may not provide the desired therapeutic concentration of the drug in the posterior segment of the eye to treat diseases there.

� Drug delivery vehicles used for topical administration include solutions, colloids, emulsions, suspensions, ointments, solid hydrophilic inserts, therapeutic contact lenses, rate-controlled release systems, and new delivery systems such as liposomes and particulates.

� Advantages of Topical Drug Delivery

� Convenient mode of administration

� Noninvasive

� Easy enough for self-administration

� Fewer systemic drug effects

� Disadvantages of Topical Drug Delivery

� Low ocular bioavailability

� Ineffectiveness in the treatment of posterior segment diseases

� Factor Affecting the Bioavailability of Topically administered Drug

� Precorneal Factors

� Precorneal fluid drainage

� After instillation of the liquid dosage form, a significant part (80

� to 90%) of it is drained into the nasolacrimal duct.

� This loss occurs primarily due to thetendency of the eye to maintain the precorneal fluid volume at 7 to 10 µl at all times as a protective physiological mechanism

� Factors influence the drainage rate are instilled volume, viscosity,

pH, tonicity, poor buffer capacity of tears and drug type

� Ocular preparation must have a pH range between 7 – 7.7

� Drug Binding to Proteins

� The protein content of tears in humans is about 0.7% of the total body protein.

� The drug binding to the tear proteins may result in a reduction

� in free drug concentrations available for pharmacological action at the target site.at the target site.

� Conjunctival Drug Absorption

� The conjunctiva is a highly vascularized mucous membrane lining the inside of the eyelids and the anterior sclera.

� Drugs are better absorbed across conjunctiva than cornea because of its greater surface area and high permeability.

� However, such nonproductive conjunctival absorption is a major precorneal loss factor and may lead to side effects,

� Systemic Drug Absorption

� A fraction of the topically applied dose that reaches the nasal mucosa through the nasalacrimal duct drainage may be absorbed systemically, leading to potential systemic side effects.

� Corneal Factors

� The cornea consists of a hydrophilic stromal layer placed � The cornea consists of a hydrophilic stromal layer placed between a lipoidal epithelial layer and a single cell layer of endothelial cells

� Corneal epithelium acts as a major barrier to the transport of hydrophilic drugs, whereas the hydrophilic stromal layer offers resistance to the passage of relatively lipophiliccompounds.

� Post Corneal Factors

� Melanin Binding

� Drug Metabolism

� Periocular Administration

� Employed for the treatment of anterior segment diseases when topical administration has failed

� They are either subconjunctival (underneath the conjunctiva) or sub-Tenon (beneath the Tenon’s capsule)conjunctiva) or sub-Tenon (beneath the Tenon’s capsule)

� Used for the administration of antibiotics or antivirals for the treatment of anterior segment pathologies.

� Intarocular Administration

� Intracameral (Injection into aqueous humor)

� Intraviteral (Injection into viterous humor)

� Severe posterior segment diseases including endophthalmitisand retinitis.and retinitis.

� Repeated intravitreal injections may cause trauma to the eye and break down the blood retinal barrier

� Transcelral Administration

� Deliver drugs to the posterior segment because of the sclera’s large surface area and high permeability characteristics

� Treatment of chorioretinal disorders, endopthalmitis, and vitreous hemorrhage.

� OCULAR FORMULATIONS� SOLUTIONS

�Most common and usually preferred

� Various excipients are usually used to maintain � Stability� Stability

� Sterility

� Increase the precorneal residence time

� Drug penetration

� Viscosity Enhancers� Help in prolonging the retention time of the drug in the precorneal area

� Decrease the lacrimal drainage of the drug

� Water-soluble polymers are used as viscosity enhancers. Cellulose derivatives including methylcellulose, carboxy methylcellulose, and hydroxy propyl methylcellulose are generally used.

� The concentration range of these polymers usually varies from 0.2 to 2.5%

� Administration of a highly viscous solution results in reflex tearing and blinking to restore the original viscosityand blinking to restore the original viscosity

� Tonicity Agents� Topically instilled solutions must be isotonic with tears.

� Instillation of a hypotonic solution results in water flow from the aqueous layer through the cornea to the surface of the eye.

� Hypertonic drops may cause discomfort or irritation owing to a dehydrating effect on the corneal epithelium.

� A 0.9% solution of sodium chloride. Tonicity agents such as sodium chloride, buffering salts, dextrose, and mannitol can be employed.

� Buffering Agents

� The physiological pH of tears is 7.4 and maintained by substances dissolved in the aqueous layer of the tears, including bicarbonate and proteins.

� Tear fluid has a small buffer capacity

Buffering agents are added in the formulation to maintain � Buffering agents are added in the formulation to maintain

� Physiological pH for preventing the irritation and discomfort to eye due to pH change by the large quantity of acid and alkali in the formulation

� To increase drug penetration by selecting pH that favoursthe unionized form of drug

� To improve drug stability

� Preservatives

� Preservative used for ocular preparations must have

� Broad spectrum of activity

� Compatibility with other ingredients

� Nontoxic and nonirritant properties

� Chemical stability

� Rapid action

� Commonly used are Quaternary Ammonium Compounds, Benzalkonium chloride, chlorobutanol, Phenyl mercuric nitrate, Methyl Paraben and Propyl Paraben

� Surfactants

� Used to solubilize and dispersed drug

� Commonly employed are non ionic surfactants such as benzalkonium chloride, benzethonium chloride, polysorbate 20, and dioctyl sodium sulphosuccinate

� SUSPENSION

� They provide slow dissolution and prolonged release of � They provide slow dissolution and prolonged release of drug.

� For optimum therapeutic effect, the rate of dissolution of particles and the rate of absorption through the cornea must be faster than the rate of loss of drug from the eye

� The particle size is generally less than 10 µm in diameter

� Streoids are usually administered in this form

� OINTMENTS

� Ointments contain one or a combination of hydrocarbons, mineral oil, lanolin, and polymers such as polyvinyl alcohol, carbopol, and methylcellulose as bases.

� Drugs administered as ointments have better bioavailability than drops primarily owing to reduced dilution of drug with the than drops primarily owing to reduced dilution of drug with the tears, prolonged corneal contact time, and reduced drainage.

� Vehicles used in ophthalmic preparations should not cause discomfort to the eye and should be compatible with other ingredients.

� The main disadvantage of ointments is that they cause blurring of vision and an increased incidence of contact dermatitis.

OCULAR INDICATION OF CONTROLLED-RELEASE SYSTEMS

Indication Drug &Disease

1. Short, topical ocular half-life Heparin for Ligneous disease

2. Small, topical ocular, therapeutic index Pilocarpine for chronic open-angle Glaucoma

3. Systemic side effects Timolol for Glaucoma and cyclosporin A for graft rejection

4. Need for combination therapy Cromoglycate and corticosteroid for Asthma and Allergies

5. Drug delivery over a prolonged period Acute corneal infections, Corneal Graft rejection episodes

6. Long-continued low dosage for therapy or prophylaxis

Prevention of Corneal Graft Rejection or Herpetic diseases,

� OCULAR INSERTS

� Ocular inserts are defined as preparations with a

� Solid or semisolid consistency,

� Whose size and shape are especially designed for ophthalmic

application (i.e., rods or shields). application (i.e., rods or shields).

� Placed in the lower fornix and, less frequently, in the upper fornix

or on the cornea.

� They are usually composed of a polymeric vehicle containing the

drug and are mainly used for topical therapy.

Lacriserts in the lower fornix

Comfort

Ease of handling

DESIRED ATTRIBUTES OF OCULAR INSERTS/OCULAR CONTROLLED

DRUG DELIVERY

Reproducibility of release kinetics

Sterility

Stability

Ease of mfg.

AdvantagesAdvantages1. Accurate dosing at a slow constant rate

2. Absence of preservative thus reducesallergic reactions

3. Increase in shelf life due to

absence of water.

4.Increased ocular residence, hence aprolonged drug activity and a higherprolonged drug activity and a higherbioavailability with respect to standard vehicles

5. Reduction of systemic absorption (whichoccurs freely with eye drops via the naso-lacrimal duct and nasal mucosa)

LimitationsLimitations• 1. Perceived by patient as foreign body.• 2. Movement around the eye.• 3. Occasional loss during sleep or while rubbing eyes.

• 4. Interference with vision.• 5. Difficulty in placement & removal.

A) NonA) Non--ErodibleErodible

1. Ocusert

2. Silicone Rubber Devices

3. Contact Lenses

4. Minidisc

B) Erodible B) Erodible

1. SODI.

2. Lacrisert

3. Collagen Shields4. Minidisc

3. Collagen Shields

C) NanoparticleC) Nanoparticle D) LiposomeD) Liposome

Types: Types:

� NON BIOERODIBLE OCULAR INSERTS� Polymers such as Ethylene vinyl acetate, silicone rubber, polymethyl methacrylate and hydroxyethyl methacrylate are used

� Placed on the cul-de-sac between the cornea and sclera

� After stated period of time, the inserts are simply removed � After stated period of time, the inserts are simply removed and discarded

� Less toxic but less convenient so less patient acceptability

� RESERVOIR DEVICE

� OCUSERTS

� Marketed by Alza Corp in 1975

� It consist of a pilocarpine reservoir with alginic acid, a mixture surrounded on either side by a copolymeric membrane of ethylene vinyl acetate.

� Around the diameter of ocusert, an ethylene vinyl acetate ring with titanium dioxide is present to provide the visibility

� The rate of diffusion is controlled by

� Polymer composition

� Membrane thickness

� Solubility of the drug

� Presence of additives� Presence of additives

� Pilo-20 and Pilo-40 are available releases drug at the rate of 20 µg/hr and 40 µg/hr

� Release kinetics is first order

� Problems are

� Cost

� Longer adaptation times for patients

� Probability of accidental expulsion

� Difficulty of handling

OCUSERTS

� MATRIX DEVICE

� SILICONE RUBBER DEVICE

� Consist of two sheets of silicone rubber glued together only at the edges with silicone adhesive

� A tube of silicone extends from the device to allow reinjection of the drug into the device when depletedof the drug into the device when depleted

� Silicone is also used for matrix fabrication of nonerodibleocular inserts

� Drug incorporation is carried out by applying heat, therefore not suitable for thermolabile drug

� Better polymer for thermolabile drug is dimethyl siloxane

� Delivers water insoluble drug 1,3, bis-(2-chloro-ethyl

a

Silicone Device (a) Before BCNU injection and (b)After BCNU Injection

b

� CONTACT LENSES

� Contact lenses both hard and soft are extensively used for correction of vision

� Only soft contact lenses are used for delivering drug

� Hard contact lenses are very much uncomfortable to wear

� Hydrophilic monomers and comonomers are used in these soft � Hydrophilic monomers and comonomers are used in these soft contact lenses

� These soft contact lenses were presoaked or fabricated to absorb aqueous solution of drugs such as pilocarpine, idoxuridine, polymyxin B, chloramphenicol and tetracycline

� Commonly used polymers are hydroxyethyl methacrylate with PVP, Ethoxy methacrylate and butyl methacrylate have been used to impart flexibility to the soft lens

� Drug release upto 180 hrs

� MINIDISCS

� Spherical discoid structure with a convex front curve and concave back curve

� 4-5 mm in diameter

� Placed behind the upper and the lower eye lid unlike soft contact lens which placed on the cornea contact lens which placed on the cornea

� Polymer used is hydroxyethyl methacrylate with ethylene glycol

� Drug release upto 168 hrs

� Sulifsoxazole minidiscs are available in market.

� BIOERODIBLE OR SOLUBLE OCULAR INSERTS

� Device are monolithic type and are meant to gradually erode, disintegrate or get solubilized to release the drug in the Cul-de-sac

� More convenient to wear

� Disadvantages are

� Losing solid integrity and getting expelled from eye

� Difficult to prevent variation in release kinetics due interpatient variability in tear fluid dynamics

SOLUBLE OPTHALAMIC DRUG INSERTS (SODI)� SOLUBLE OPTHALAMIC DRUG INSERTS (SODI)

� Small water soluble developed for Cosmonauts who could not use their eye drop in liquid condition

� Example of soluble inserts are available for various drugs such as Atropine, pilocarpine, neomycin, kanamycin, tetracycline, idoxuridine

� Composition : Acryl amide, Vinyl Pyrolidone, Ethylacrylate.� Weight 15-16 mg.� In 10-15 sec Softens;� In 10-15 min. turns in Viscous Liquids;� After 30-60min becomes Polymeric Solution.� Single SODI application a day :replaces 4-12 eye drops InstillationInstillation

� or 3-6 application of Ointments� COLLAGEN SHIELDS

� Marketed by Bausch and Lomb as BioCor-12, BioCor-24 and BioCor-72 for delivering the drug upto 12, 24 and 72 hrs

� Collagen shields are presoaked with drug solution thereby providing rapid release of drug

� Used for delivering many drugs such as gentamicin, tobramycin, vancmycin etc

� Causes ocular inflammation

Collagen Shields

� LACRISERTS

� Sterile, Rod Shaped device.

� Composition: HPC without preservative.

� Weight:5mg,

� Dimension 1.25mm and Length:3.5mm

� Placed in lower conjunctiva with applicator

� Use:-Dry eye treatment, Keratitis Sica.

� Problem of blurring of vision and difficulty of inserting the device

� LIPOSOMES

� Positively charged due to negatively charged surface on the corneal epithelium. Results in increase precorneal residence

� Degree of dissociation between corneal epithelium and liposomes followed the order MLV+ > SUV+ > MLV- > SUV+ > MLV > SUVMLV > SUV

� Usually polymer coated MLV was used for increase corneal retention

� Common polymers are Carbopol 934 and Carbopol 1342 as mucoadhesive

LIPOSOMES

�OCULAR IONTOPHORESIS

� Iontophoresis is a method of drug delivery that utilizes electric current to deliver ionized molecules to the intraocular tissues.

� To drive the molecules into the tissue either a cathode or an anode is used, depending on the charge of the molecule. Drugs can be delivered to the cornea or the sclera.can be delivered to the cornea or the sclera.

� Transcorneal iontophoretic delivery of antibiotics such as gentamicin and aprofloxacin for treatment of bacterial keratitis

� Transscleral iontophoresis can be used to directly deliver drugs to the vitreous for treating posterior segment diseases. It may produce discomfort and small areas of necrosis at sites of application.

Iontophoresis

� NANOPARTICLE TECHNOLOGY

For water soluble drugs.

Size:10-1000nm

Drug is Dispersed, Encapsulated, or Absorbed Drug is Dispersed, Encapsulated, or Absorbed

Produced by Emulsion Polymerization

Polymerization is carried out by :

• Chemical initiation, Gamma irradiation, Visible light.

Emulsifier stabilizes polymer particle

Polymer used are Biodegradable.

E.g. :- Nanoparticle of Pilocarpine enhances Mitotic response by 20-23%.

� POLYMERS IN OCULAR DRUG DELIVERY

� Polymers are macromolecules formed from many repeating small units called monomers, which are connected by covalents bond. Each macromolecules is a unit and not an aggregateunit and not an aggregate

� CLASSIFICATION

� SYNTHETIC POLYMERS

� Synthetic polymers usually have less than 10 repeating subunits whereas the natural polymers, particularly proteins and enzymes, may have more than 20 repeating sub units

� Synthetic polymers can be classified into different categories based on their preparation, structure, repeating units, stereoregularity, and the adjacent chain interactions

� Based on Preparation

� Condensation polymers (or step reaction polymers) are essentially polymers in which the monomer units are joined by eliminating a water molecule in each step.

� Examples are polyester, polyurethane and polyurea

� Addition Polymer are obtained by joining monomer units by � Addition Polymer are obtained by joining monomer units by double bond.

� Examples are polyethylene, polyvinyl chloride, polystyrene and polymethacrylate

� Based upon structure

� Linear Polymers

� Examples are linear polystyrene

A A A A

� Branched Polymers

� Star shaped and comb-shaped polystyrene

A A A A

A

A

� Based Upon Repeating Units

� Homopolymers – With identical repeating subunits such as

A-A-A . For example Polymethyl methacrylates

� Copolymers -with different repeating subunits such as Diblockcopolymers i.e. A-A-A-B-B-B and Random polymers A-B-B-A-B-A-A. Examples of this copolymers are acrylates and A-B-A-A. Examples of this copolymers are acrylates and methacrylates

� Based Upon Stereoregularity

� Atactic-There is no regularity of R groups

� Isotactic Polymers

� There is a regularity of R group

� Syndiotactic Polymers

� The trans and gauche forms alternate

CH2 CH CH2 CH CH2 CH CH2 CH

R R

R

R

R R

Atactic Polymers


R R

R R


R R RR

Isotactic Polymers

Syndiotactic Polymers

� Based upon Adjacent Interactions

� Polymers are subclassified into elastomers, plastics, fibers or cellulosics.

� In elastomers the chain are attracted to each other by London Forces (e.g. Polyethylene)

� In Plastics the chains are attracted by London as well as the � In Plastics the chains are attracted by London as well as the Keesom forces (e.g. PVA)

� Fibers or cellulosics are polymers in which the chain are attracted by London forces, Keesom forces and hydrogen bonding

� NATURAL POYMERS

� PROTEINS AND PEPTIDES

� The building blocks of proteins are aminoacids which are bound by a peptide bond.

� A peptide bond is an amide linkage between the amino group of one molecule and the carboxyl group of anotherof one molecule and the carboxyl group of another

� Proteins are made up of a single polypeptide or a group of polypeptides

� Enzymes are proteins with catalytic activities.

� Hormones, the secretion of endocrine glands are also proteins

� Proteins are classified as

� Simple Proteins-Albumin, Globulin, Histones, Collagen

� Conjugated Proteins

� Nonprotein i.e. nucleoproteins (Protein + Nucleic Acid)

� Phospho proteins (Protein + Phosphoric acid)

� Glycoproteins (Protein + Carbohydrate)

� Chromoproteins (Protein + Color compounds)

� Lipoproteins (Proteins + Fatty acids)

� Membrane proteins (Protein with membranes)

� NUCLEIC ACIDS AND SUGARS� Nucleic acids are made up of building blocks called nucleotides

� Each nucleic acids consist of base, sugar and phosphate

� Major nucleotides are uridylic acid, cytidilic acids, deoxythymidylic acids, adenylic acids and guanylic acids

� The sugars polymers, made up of glucose units as building blocks, for e.g. Starch and Celluloses

� Starch consist of alpha glucose units. Mainly of three types

� Amylose – Straight chain Plant starch

� Amylopectin – Branched chain plant starch

� Glycogen-A branched chain animal starch� Glycogen-A branched chain animal starch

� Cellulose is made up of Beta glucose units, a principle constituents in plant cells