“Nanoantibiotics”: A new paradigm for treating infectious diseases using

nanomaterials in the antibiotics resistant era

By

N. MOHAMED FAIZEE

13-PCH-19

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NanoAntibiotics

The Nano Particles (NPs) are physical attracted to the infected cells by

breaking their walls without destroying the healthy cells around them.

Various nano sized drug carriers are efficiently involved in improving

pharmacokinetics and accumulation which will reduce adverse effect of

antibiotics.

These NPs retained in our body longer time for achieving sustained

therapeutic effects.

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Antibiotic Resistance It is the ability of microorganisms to withstand the effects of an antibiotic.

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Limitations of Current Antibiotics Use of antibiotics started with production of penicillin in 1942s after that

many new antibiotics were developed.

Evolving of microorganisms creating infectious diseases and antimicrobial

resistance against the new antibiotics.

Some bacteria are untreatable by the antibiotics such as vancomycin-

resistant S. aureus (VRSA) and methicillin-resistant S. aureus (MRSA).

Because their spores are highly resistant and very thick harder to enter the

drug inside the cell and not affected by antibiotics.

This shows that treating this virulent bacteria with antibiotics is extremely

difficult.

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FDA approval for new antibiotics also become less in each year due to

ineffectiveness against bacteria.

For this discovery and delivery of antimicrobial drugs with improved

efficacy, and avoidance of resistance are highly demanded.

These limitations leads to Nanotechnology in immunization, for controlling

infectious diseases and overcoming antibiotic resistant pathogens.5

Nanotechnology for Identifying Infection

It is new method for identifying and preventing the growth of pathogenic

bacteria.

Toxic shock syndrome(TSS) is a serious disease caused by a toxin produced

by Staphylococcus aureus bacteria. It occurs during skin infection, burns,

wound infection.

For that Scientist from University of Bath, UK created an advanced wound

dressing that can detect the key bacteria causing TSS.

This new material can automatically detect infection by pathogenic bacteria

and respond to this by releasing an antibiotic into the wound.

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This smart wound dressing system that only releases an encapsulated

antimicrobial agent in the presence of pathogenic bacteria, without

responding to harmless bacteria.

Nanocapsules which releases an dye when it detects and kill the bacteria and

give the colour under UV light.

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The researchers have demonstrated the effectiveness of their system for two

pathogenic species of bacteria, P. aeruginosa and S. aureus.

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Mechanism of Nanoantibiotics

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Enhanced Antibacterial Activity of Nanocrystalline ZnO

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Introduction Nanosized inorganic particles, exhibit unique physical, chemical, and

biological properties. Metal oxides in nanometer sized shows theirelectromagnetic, optical and catalytic properties.

Normally, metal oxides NPs are synthesized by chemical methods, but thereby sonochemical technique is used for synthesizing crystalline NPs.

Organic antibacterial agents have limited their application, such as low heatresistance, high decomposability and short life.

Inorganic antibacterial agents are thermally stable and longer lasting,chemically durable and effective against a bacteria / fungi and even cancercells.

The stability is due to Particle size, shape and surface area, Electronic statessuch as valence and conductance states.

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Preparation of ZnO NPs ZnO NPs is produced by an sonication method . An appropriate ultrasonic

energy is required to induce collapsing gas bubbles which agitate the particleswith high temperature.

The implosive collapse of the bubbles generates a localized hot spots ofextremely high temperature and high pressure powerful ultrasound radiation(20 kHz) and having high cooling rates responsible for crystal formation.

.

The sonochemical method is advantageous as it is nonhazardous, rapid inreaction rate and produces very small metal particles.

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Different types of ZnO NPs were prepared,

Zinc oxide with 10% water- DMF

Zinc oxide with water, and

Commercial Zinc oxide.

In this 10% water–DMF solution reaction gives a better yield than with

water alone that is due DMF, which generated a smaller nanoparticles and

a more uniform crystal growth.

The product yields with water and water–DMF were 56% and 73%

respectively.

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Results and Discussion

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X-ray diffraction patterns of ZnO NPs

The average crystallite size, Debye-

Scherrer formula,

cos

89.0L

L - Average crystallite size (nm)

λ - X-ray wavelength (nm)

β - full width at half maximum (FWHM)

θ - Bragg angle of the plane15

In XRD pattern,

a (ZnO-3) = Commercial zinc oxide sample,

b (ZnO-2) = Zinc oxide with water sample,

c (ZnO-1) = Zinc oxide with 10% water- DMF sample.

Here ZnO samples synthesized in the water–DMF medium, the peaksobtained were more line-broadened due to the small nanometer-scalecrystal size.

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TEM images ZnO NPs

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HR-TEM images ZnO NPs

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The ZnO in water NPs are mostly monodispersed but they form network

structure which shows that particle is synthesized in the water medium.

It shows that it has a stronger tendency to aggregate and to form soft

agglomerates in the aqueous medium due to that interparticle interactions

will be generated.

But these interactions are reduced in the 10% water–DMF solution, due to

the capping of the particles by the DMF.

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Antibacterial activity of ZnO against E. coli and S. aureus

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Antibacterial Test against S. aureus

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Effect of Zinc oxide with 10%

water- DMF sample

Untreated S. aureus Cells

Due to the large sized nanoparticles, ZnO NPs were not able topenetrate the cell, ROS activity is observed and destroying the cellmembrane.

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S. aureus with Large Sized NPs

Antibacterial Test against E.coli

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E. coli Cell with two NucleoidsUntreated E. coli Cells

Inhibition Test for E. coli

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Without ZnO NPs Effect of Zinc oxide with 10%

water- DMF sample

By using the sonochemical method smaller sized NPs is obtained, which

shows an enhanced antibacterial activity.

The more efficient antibacterial activity against E. coli and S. aureus is due

using smaller sized NPs.

These smaller NPs shown more cellular internalization observed in TEM,

and percentage of reduction in viability seen in antibacterial test.

Between these two bacteria, E. coli was affected more than S. aureus due to

weaker antioxidant in cell which shows less resistant to OS, and having thin

peptidoglycan cell wall for easy penetration by NPs.

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NPs in Drug Delivery

Targeted drug delivery: Delivering a drug to a specific site in the bodywhere it has the greatest effect, instead allowing it to diffuse to varioussites which may cause damage or side effects.

Controlled drug delivery: Which delivers the drug at a predeterminedrate, by systematically at specified period of time.

The nanoparticles are effective for drug delivery, it find the diseased cells

very precisely and carry the medicine to that place. By using less dosage

and thereby fewer side effects.

In that polymeric NPs have very high surface areas, drugs may also be

adsorbed on their surface. Their nanometer-size promotes effective

permeation through cell membranes and stability in the blood stream.

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Entrapment or Encapsulation

During the 1970, scientists first began to encapsulate and entrap drugs within

polymers.

Encapsulation involves surrounding drug molecules with a solid polymer shell.

Entrapment involves the suspension of drug molecules within a polymer matrix.

drug

polymer

Drug

Polymer

Drug Release by Diffusion

Early encapsulation and entrapment systems released the drug from within the

polymer via molecular diffusion.

When the polymer absorbs water it swells in size,

Swelling created voids throughout the interior polymer,

Smaller molecule drugs can escape via the voids at a known rate

controlled by molecular diffusion (a function of temperature and drug

size).

Add

water

Add

time

Targeting Cancer with a Triple Threat The first polymer NPs that carry a defined ratio of three cancer drugs and

release them with three independent triggering mechanisms against Ovarian

cancers.

Doxorubicin, camptothecin, and cisplatin are a standard combination therapy

for aggressive ovarian cancers.

Instead of attaching drugs to NPs, they synthesized NPs from drug-containing

building blocks. In two building blocks, the researchers linked doxorubicin or

camptothecin to a norbornene monomer (along with a protective PEG group).

In a third unit, they inserted cisplatin between two norbornene monomers to

form a cross-linking agent. By the new method of ring-opening metathesis

polymerization (ROMP).

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Mechanism of Drug Release There is no limitation on how many drugs you can add, and the ratio of

drugs carried by the particles just depends on in the beginning how they are

mixed together.

Each particle carries the three drugs in a specific ratio that matches the

maximum tolerated dose of each drug, and each drug has its own release

mechanism.

Cisplatin is freed as soon as the particle enters a cell, as the bonds holding it

to the particle break down on exposure to glutathione. Camptothecin is also

released quickly when it encounters cellular enzymes called esterases.

The third drug, doxorubicin, it would be released only when ultraviolet light

shines on the particle. Once all three drugs are released, the left behind is

PEG, which is easily biodegradable.

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Drugs Ratio

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Drug Release of Cisplatin & DOX

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Cisplatin and DOX in Ovarian Cells

Advantages and disadvantages of antimicrobial NPs over free antimicrobial agents

Antimicrobial NPs :

Advantage:

• Targeted drug delivery via specific accumulation

• Lowered side effects of chemical antimicrobials

• Extended therapeutic lifetime due to slow elimination

• Controlled drug release

• Broad therapeutic index

• Low cost

Disadvantage:

• High systemic exposure to locally administrated drugs

• Nanotoxicity (lung, kidney, liver, brain, germ cell, metabolic, etc.)

• Lack of characterization techniques.

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Free antimicrobial agents Disadvantage

No specific accumulation

High side effects of chemical antimicrobials

High antimicrobial resistance

Short half life due to fast elimination

Poor solubility

High cost

Advantage

Absence of NPs in the whole body

Absence of nanotoxicity

Well-established characterization techniques

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Conclusion

Antibiotics have been saving an enormous number of lives from many

infectious diseases, but due to the effect antibiotic resistance by microbes

more powerful antibiotics is needed.

For that nanotechnology helping in many ways through nanodevices,

detecting bacteria by NPs, targeted and controlled drug delivery by NPs and

enhanced antibacterial activities by NPs.

These are possible due to high surface area to volume ratio and unique

physico-chemical properties exhibited by NPs.

NPs prevent drugs from interacting with normal cells, thus avoiding side

effects.

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References [1] Ae Jung Huh, Young Jik Kwon, Journal of Controlled Release 156

(2011) 128–145.

[2] Guy Applerot, Anat Lipovsky, Rachel Dror, Nina Perkas, Yeshayahu

Nitzan, Rachel Lubart, and Aharon Gedanken*, Adv. Funct. Mater. 2009, 19,

842–852.

[3] Muhammad Ali Syed and S. Habib Ali Bukhari∗ J. Biomed.

Nanotechnol. 2011, Vol. 7, No. 2.

[4] Charalambos Kaittanis, Santimukul Santra, and J. Manuel Perez, Adv

Drug Deliv Rev. 2010 March 18; 62(4-5): 408–423.

[5] Longyan Liao, Jenny Liu,Erik C. Dreaden, Stephen W. Morton, Kevin E.

Shopsowitz, Paula T. Hammond, and Jeremiah A. Johnson, J. Am. Chem.

Soc. 2014, 136, 5896−5899.

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The Next Generation of

Antibiotics