BIODEGRADATION OF POLYMERS

POLYMERS AND ENVIRONMENTKEJ 4604GROUP 2

NAME : MUHAMMAD HELMI BIN SAPERI (UK29519) : MOHD SYUKRI BIN ABDULLAH (UK29529)

LECTURER : ASSOCIATE PROF DR MOHAMAD AWANGDATE : 22 MARCH 2016SEMESTER : II 2015/2016

APPLICATION

MECHANISM

INTRODUCTION

CLASSIFICATION

BIODGRADABLE POLYMERS

TALK LAYOUT

FACTORS

INTRODUCTION Polymer is derivation of ancient

Greek word ‘Polus’ which means many, much and ‘Meros’ means parts.

Refers to molecule whose structure is composed of multiple repeating units

In general, polymer is a large molecule (macromolecule) composed of many repeating subunits (monomers) which linked via various ways to give linear, branched and cross linked polymer etc.

Examples of monomers & Polymers

What do we mean by ‘biodegradable polymer’ ?

• Based on Europian Union norm EN13432 defines as: “one possessing biodegradability (i.e. converted into carbon dioxide under microbial action‟), disintegrability (i.e. fragmentation and loss of visibility in the final compost), and an absence of negative effects in the final compost (e.g. a low level of heavy metals).‟

• 140 million tonnes of synthetic polymers produced each year

• In Western Europe, 7.4% of MSW are plastics which classified as 65% polyethylene/polypropylene, 15% polystyrene, 10% PVC, 5% polyethylene terephthalate and others

• Major problem in wastewater

INTRODUCTION – Cont’

WHAT TO DO

Combustion? Discharges of toxic compounds (e.g. Dioxin)

Landfill? (dry & anaerobic) Biodegradable polymer will not degrade

as biodegradation process mediated by microorganism/enzymes and require water and oxygen (aerobic condition)

Does not decompose

Inert and won’t react with what stored in them

Durable and won’t easily

decay

PLASTICS

Since they do not decompose, the answer is to recycle the plastics, so they can be remade into something else. Here we see a bunch of CDs getting recycled

WHY POLYMERS IS POPULAR?

Inexpensive and easy to fabricate

Light and strongAbundant and

versatile

APPLICATIONS

LDPEHDPE PE PVC

i) Natural Polymer : from nature (plant and animals)a) Collagenb) Albuminc) Dextrand) Gelatin

ii) Synthetic Polymer : man made polymersa) Polyethylene (HDPE, LDPE, PET)b) Polyvinylchloride (PVC)c) Polypropylene (PP)d) Polystyrene

CLASSIFICATION

Natural PolymersPolymers DetailsCollagen found in mammals and provider of strength to tissues

Use for biomedical applications such as surgery, cosmetics and drug delivery

Poor dimensional stability and mechanical strength

Albumin Major plasma protein componentUsed for designing particulate drug delivery system like insulin

and SulphadiazeneUsed in chemotheraphy in order to achieve high local drug

concentration for longer timeDextran Complex branched polysaccharide made of many glucose

molecules joined into chains of varying lengthsUsed for colonic delivery of drug in the form of gels

Gelatin Mixtures of peptides and proteins produced by partial hydrolysis of collagen and extraction of boiled bones, connective tissues and

organsUsed as coating materials and oral controlled delivery of drugs

Synthetic Polymers

Synthetic or Natural Biodegradable PolymersWhy Do We Prefer Synthetic Ones?

Tailor-able properties Predictable lot-to-lot uniformity Free from concerns of immunogenicity Reliable source of raw materials

FACTORS AFFECTING BIODEGRADATION OF POLYMERSMorphological factors•Shape & size•Variation of diffusion coefficient and mechanical stressesChemical factors•Chemical structure & composition•Presence of ionic group and configuration structure•Molecular weight and pressure of low molecular weight compoundsPhysical factors•Processing condition•Sterilization process

Biodegradable Polymers Classification

• Variety of available degradable polymers is limited due to stringent requirements– biocompatibility– free from degradation related toxic

products (e.g. monomers, stabilizers, polymerization initiators, emulsifiers) • Few approved by FDA

• PLA, PLGA are used routinely

Polyesters

• Most degradable polymers are polyesters• ester is a covalent bond with polar nature,

more reactive• can be broken down by hydrolysis• the C-O bond breaks • ESTER BOND

Ester production

Poly(glycolic acid) (PLGA) & Poly(lactic acid) (PLA)

Poly(caprolactone) (PCL)

Most widely used biodegradable polymerPGA is the simplest aliphatic polyesterhighly crystalline, high melting point, low solubilityPLA is more hydrophobic than PGAhydrophobicity of PLA limits water uptake of thin films to about 2% and reduces the rate of hydrolysis compared with PGAD,L-PLA used as drug delivery due to it is an amorphous polymerL-PLA used in mechanical applications (orthopaedic devices) due to its semicrystalline characteristicsPLGA with different ratios used for drug delivery with different degradation rate

semi-crystalline polymerslower degradation rate than PLAremains active as long as a year as a drug delivery agentCapronor®, implantable biodegradable contraceptiveimplanted under skindissolve in the body and does not require removaldegradation of the poly(epsilon-caprolactone) matrix occurs through bulk hydrolysis of ester linkages, which is autocatalyzed by the carboxylic acid end groups of the polymer, eventually forming carbon dioxide and water, which are absorbed by the body

Poly(amides)• contain a peptide (or amide) link• can be broken down by hydrolysis• the C-N bond breaks• can be spun into fibres for strength• AMIDE BOND

Poly(anhydrides) highly reactive and hydrolytically unstable degrade by surface degradation without the need for catalysts aliphatic (CH2 in backbone and side chains) poly(anhydrides)

degrade within days aromatic (benzene ring as the side chain) poly(anhydrides) degrade

over several years aliphatic-aromatic copolymers can be used to tailor degradation rate excellent biocompatibility & used in drug delivery

Poly(orthoesters)

formulated so that degradation occurs by surface erosion

drug release at a constant rate degradation rate adjusted by acidic and

basic excipients (acidic excipients increasing degradation rate)

Poly(amino acids) • poly-L-lycine, polyglutamic acid• Amino acid side-chains offer sites for drug attachment• low-level systemic toxicity owing to their similarity to

naturally occurring amino acids• artificial skin substitutes• limited applicability as biomaterials due to limited

solubility and processsibility• polymers containing more than three or more amino

acids may trigger antigenic response

Other polymers• Poly(cyanocrylates)

– used as bioadhesives– use as implantable material is limited due to

significant inflammatory response• Poly(phosphazenes)

– inorganic polymer– backbone consists of nitrogen-phosphorus

bonds– use for drug delivery under investigation

Polymer Degradation• Polymer degradation:-

change of properties tensile strength, colour, shape and etc of polymer –based product under the influence of one or more environmental factors: heat, light or chemicals (acids/alkalis and salt)

Chemical degradation Degradation by hydrolysis to give lower molecular weight molecules. Hydrolysis takes place in the presence of water containing acid or base

Biological degradation Biologically degraded by microorganism to give lower molecular weight

Mechanical degradation polymer chain is ruptured by mechanical means. The effect is to reduce the polymer molecular mass.

Chlorine induce cracking Chlorine – highly reactive gas that attack susceptible polymers such as acetal resin and polybutylene pipe work

Thermal degradation Molecular deterioration as a result of overheating by breaking down its molecular chain

Photo degradation Known as weathering process that resulting in discoloration and loss of mechanical properties

Degradation

Reaction Paths of Polymer Degradation

Mineralization Process

- Small variations of polymer chemical structures effects its biodegradability

- Biodegradability depend on molecular weight, molecular form and crystallinity

- Increase in molecular weight lead to decrease in biodegradibility

- Enzymes (extracellular & Intrcellular depolymerases) involved in depolymerization process

• The term ‘Biodegradation’ is limited to the description of chemical processes which is chemical changes that alter the molecular weight or solubility of polymer

• ‘Bio-erosion’ is restricted to physical processes that result in weight loss of a polymer device

• Two types of bio-erosion of polymers are bulk erosion and surface erosion

Mechanism of Biodegradable Polymers

Types of bioerosionBulk erosion• Happens throughout the

sample• Ingress of water faster

than the rate of degradation

• Ex: Polylactic acid (PLA)

BULK EROSION

Types of bioerosion - ContSurface erosion• Sample eroded from the

surface• Mass loss is faster than

the ingress of water in the bulk

• Ex: Polyanhydrides

CLEAVAGE OF CROSSLINK

TRANSFORMATION OF SIDE CHAINS

CLEAVAGE OF BACKBONE

ENZYMATIC DEGRADATION

• Enzymatic degradation – mediated by water, enzymes and microorganisms.

ADVANTAGES OF BIODEGRADABLE POLYMERS

•Decrease in dosing frequency•Localized delivery of drug•Sustained delivery of drug•Stabilization of drug•Reduce side effects•Improved patient compliance•Controllable degradation rate

Medical Applications of Biodegradable Polymers

Wound management Sutures Staples Clips Adhesives Surgical meshes

Orthopedic devices Pins Rods Screws Tacks Ligaments

Dental applications Guided tissue

regeneration Membrane

Void filler following tooth extraction

Cardiovascular applications Stents

Intestinal applications Anastomosis rings

Drug delivery system Tissue engineering

• Polymers are everywhere• Polymer degradation

reducing molecular weight, destroyed crystallinity and diminish physical properties of polymers

• Most biodegradation is enzymatic hydrolysis or oxidation

• Landfill is still a problem!

CONCLUSION

Glossary of TermsBiodegradable plastics : Plastics that will fully decompose to carbon dioxide, methane, water, biomass

andinorganic compounds under aerobic and anaerobic conditionsAerobic decomposition : Biological decomposition in the presence of oxygen or air, where carbon isconverted to carbon dioxide and biomassAnaerobic decomposition : Biological decomposition in the absence of oxygen or air, where carbon isconverted to methane and biomassBiological decomposition : Decomposition under the influence of biological systemBiomass : Substance of biological origin, with the exception of geological formations and fossilizedbiological matterBioplastics : Plastics that are biodegradable and/or biomass-basedOXO-Biodegradable : Degradation resulting from oxidative and cell mediated phenomena eithersimultaneously or successivelyBiopolymers : Polymers produced by living organismBiodegradation: A biological agent (an enzyme, microbe or cell) responsible for degradationBioerosion: A water-insoluble polymer that turns water soluble under physiological conditions withoutregard to the mechanism involved during erosion. Bioerosion contains both physical (such as dissolution)and chemical processes (such as backbone cleavage). Bioresorption, Bioabsorption: Polymer or its degradation products removed by cellular activity

REFERENCE• Kumar, A. A., Karthick, K., & Arumugam, K. P. (2011). Properties of

biodegradable polymers and degradation for sustainable development.International Journal of Chemical Engineering and Applications, 2(3), 164.

• Krzan, A. (2012). Biodegradable Polymer and Plastic.• Leja, K., & Lewandowicz, G. (2010). Polymer biodegradation and

biodegradable polymers—a review. Polish Journal of Environmental Studies,19(2), 255-266.

• Premraj, R., & Doble, M. (2005). Biodegradation of polymers. Indian Journal of Biotechnology, 4(2), 186-193.

• Vroman, I., & Tighzert, L. (2009). Biodegradable polymers. Materials, 2(2), 307-344.

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