Advance polymers(607)

Biopolymers

Dr. Misbah Sultan

Books

Biorelated Polymers

Sustainable Polymer Science & Technology

[Emo Chiellini, Helena Gil, Gerhart Braunegg, Johanna Buchert, Paul Gatenholm, Marten Van der Zee]

Biomaterials

An Introduction

[Joon Parks & R. S. Lakes]

Biomaterials

Principals & Applications

[Joon B. Park & Joseph D. Bronzino]

Contents

Biopolymers introduction Biorenewable polymers• Carbohydrates • Proteins • Lipids • Nucleic acids Biomaterials

What are Biopolymers?

Biorenewable Biodegradable

Biomaterials

Any biorelated polymeric material

Properties of Biopolymers

• Renewable• Sustainable• Biodegradable• Non-Toxic• Non-Immunogenic• Non-Carcinogenic• Non-Thrombogenic • Carbon neutral

Applications of Biopolymers • Coatings• Fibers• Plastics• Adhesives• Cosmetics• Oil Industry• Paper• Textiles/clothing• Water treatment• Biomedical• Pharmaceutical• Automotive• Rubber

Why Biopolymers???

• Carbon neutral…low environmental footprints

Petrochemicals will eventually deplete

Biopolymers are

Renewable & Sustainable industry

Biorenewable biopolymers

• Polymers of biological origin Carbohydrates…..starch Proteins……haemoglobinNucleic acids….DNALipids…..

Carbohydrates

Carbohydrates

Carbohydrates are organic compounds

1C:2H:1OSource of energy……..sugarsStore of energy………..starch Structural materials….polysaccharides Components of other molecules e.g. DNA,

RNA, glycolipids, glycoproteins

Tree of Carbohydrates

Monosaccharide

Disaccharide

Oligosaccharide

Polysaccharide

Monosaccharide

• Single monomer of carbohydrate….glucose • Simple sugar• 1C:2H:1O• A source of quick energy

Common Monosacchrides

• Glucose – main source of energy

• Fructose – fruits sugar/sweetest sugar

• Galactose – milk sugar

GlucoseStructural formula.

Straight chain glucose

H-C=O | H-C-OH |HO-C-H | H-C-OH | H-C-OH | CH2OH

Glucose glucose bending

GlucoseTwo ring-shape

versions

alpha-glucosealpha-glucose

beta-glucosebeta-glucose

Glucose bends itself into 4 different shapes millions of times

a second

1

4

6

2

3

5

Used in making

cellulose

Used in making starch

flips either way bends

Monosaccharide isomers

Galactose Glucose Fructose

Same molecular formula, but different structural formulas

Disaccharides

• “Di” means two• Two monosaccharides combine• Common Disaccharides are

- Lactose (found in milk)

- Maltose

- Sucrose (table sugar)

Disaccharides

Maltose

Sucrose Lactose

Polysaccharides

Poly means……..manyLarge sugarsStructural materials

Examples • Glycogen• Starch• Chitin• Cellulose

Functions of the Polysaccharides

• Glycogen…….animals energy storage

• Starch……… plants energy storage

• Cellulose ……… cell walls

• Chitin………… the exoskeleton of arthropods

Polysaccharides

Cellulose

Polysaccharides

Starch

Natural synthesis of carbohydrates

Proteins

Proteins

• Polymers of amino acids covalently linked through peptide bonds

• Natural organic molecules….C, H, O, N• Monomers…….amino acids

Building blocks of proteins

• There are 20 different amino acids• All 20 amino acids share the same basic structure• Every amino acid contains

- an amino group

- a carboxyl group

- a hydrogen atom

- a central carbon atom

- R (alkyl/aryl) group

Amino Acid Structure

R Groups of amino acids

• Difference in amino acids…….. R groups• R group……simple or complex• R groups…different shapes & characteristics

Peptide bond -COOH group of one amino acid joined with

the -NH2 group of the next amino acid through condensation polymerization

Polypeptide

• A long chain of amino acids…POLYPEPTIDE

• Proteins are composed of one or more polypeptides

Role of Proteins

• Structural roles…….cytoskeleton• Catalysts……enzymes• Transporter………ions and molecules• Hormones

Common example of Proteins

• Many enzymes are proteins• Biological catalysts• Lower the activation energy of chemical

reactions• Increase the rate of chemical reactions

Structure of Proteins

Sensitivity of Proteins

• Temperature• pH• Denature proteins

LIPIDS

Lipids

• Large, nonpolar organic molecules• LIPIDS do NOT Dissolve in Water!• Have a higher ratio of carbon and hydrogen

atoms to oxygen atoms than carbohydrates• Lipids store more energy per gram than other

organic compounds

Categories of Lipids

• Fatty Acids• Triglycerides• Phospholipids• Waxes and Oils• Steroids

Fatty Acids

• Linear carbon chains • On one end of the carbon chain is a carboxyl

group• On the other end of the carbon chain is a

methyl group

Fatty acid chain

• The carboxyl end is polar and is hydrophilic• The carboxyl end will dissolve in water• The methyl end is nonpolar and is

hydrophobic• The methyl end will not dissolve in water

Types of Fatty Acids

• Unsaturted fatty acids……carbon chain contains double bonds

• Saturated fatty acids……carbon chain contains single bonds

Triglycerides• One molecule of glycerol and three fatty acid

chains

• Saturated triglycerides…butter, fats and red meat• Unsaturated triglycerides….plant seeds

Phospholipids• One glycerol + two fatty acids + one

phosphate group• Compose cell membranes

Waxes• A long fatty acid chain joined to a long

alcohol chain• Waterproof • Form a protective coating in animals & plants

Steroids

• Four fused carbon rings…..cholesterol• Many animal hormones are steroid compounds

Nucleic Acids

Nucleic Acids

• Large and complex organic molecules that store and transfer genetic information in the cell

• Types of nucleic acids

i. DNA =deoxyribonucleic acid

ii. RNA = Ribonucleic acid

Building blocks of Nucleic Acids

• Monomers of nucleic acids are nucleotides• Components of a nucleotide

- nitrogen base

- sugar

- phosphate

Deoxyribonucleic acid (DNA)

• Double helix• Found in the nucleus• Stores hereditary information

Ribonucleic acid (RNA)

• Is a single helix• Can be found in the

nucleus and the cytoplasm of the cell

• Helps build proteins• Can act as an

enzyme

?????????

Difference between biorenewable biopolymers and synthetic

polymers????

BiomaterialsScience for the benefit of life

Biomaterials Any material used to make devices to replace a part or a function of the living body in a safe, reliable, economic &

physiologically acceptable manner

OR

Any material used to replace part of a living system or to function in intimate contact with living tissue

OR

A pharmacologically inert substance designed for implantation within or incorporation with living system

Natural/synthetic/blend

e.g. sutures, tooth fillings, bone replacements, artificial eyes etc.

Biomaterials market

Success of Biomaterial

• Properties & biocompatibility• Health condition of recipient• Competency of the surgeon

Required characteristics of a Biomaterial

1. Biocompatibility

2. Pharmacologically acceptable

3. Chemically inert & stable

4. Adequate mechanical strength

5. Sound engineering design

6. Proper weight & density

7. Cost effective

8. Reproducible

9. Easy to process at large scale

Types of Biomaterials Materials Advantages Disadvantages Examples

Polymers (nylon, silicon, polyester)

ResilientEasy to fabricate

Not strongDeform with timeMay degradable

Suture, blood vessels, hip sockets

Metals (Ti and its alloys, Ag, Au, stainless steels)

Strong, tough, Ductile

May corrodeDenseDifficult to prepare

Joint replacement, dental root implant, pacers, bone plates and screws

Ceramics (alumina, zirconia, hydroxyapetite)

Very Biocompatible

BrittleNot resilient

Dental and orthopaedic implants

Composites (carbon-carbon, bone cement)

Strong Tailor made

Difficult to prepare Dental resin, bone cement

Polymeric Biomaterials

• Natural polymeric biomaterials

Collagen, Chitosan, Alginate• Synthetic polymeric biomaterials

PVC, PP, PS, PU• Degradable polymeric biometrials

PLA, PGLA

Natural Polymers as Biomaterials

Polymers derived from living creatures“Scaffolds” grow cells to replace damaged

tissue• Biodegradable• Non-toxic• Mechanically similar to the replaced tissue• Capable of attachment with other molecules

Natural polymers used as biomaterials– Collagen, Chitosan and Alginate

Collagen

• Consist of three intertwined protein chains, helical structure

• Collagen…..non-toxic , minimal immune response

• Can be processed into a variety formats– Porous sponges, Gels, and Sheets

• Applications– Surgery, Drug delivery, Prosthetic

implants and tissue-engineering of multiple organs

Chitosan• Derived from chitin, present in hard exoskeletons

of shellfish like shrimp and crab• Chitosan desirable properties – Minimal foreign body reaction– Mild processing conditions– Controllable mechanical– biodegradation properties

• Applications– In the engineering of cartilage, nerve, and liver tissue,– wound dressing and drug delivery devices

Alginate• A polysaccharide derived from brown

seaweed

-Can be processed easily in water

-non-toxic

-Biodegradable

-controllable porosity• Forms a solid gel under mild processing

conditions• Applications in

Liver, nerve, heart, cartilage & tissue-engineering

Synthetic Polymers as Biomaterials

• Advantages of Synthetic Polymers– Ease of manufacturability– process ability– reasonable cost

• The Required Properties– Biocompatibility– Sterilizability– Physical Property– Manufacturability

• Applications– Medical disposable supplies, Prosthetic materials, Dental

materials, implants, dressings, polymeric drug delivery, tissue engineering products

Biodegradable Polymers as Biomaterials

• Advantages on biodegradable polymer– Didn’t leave traces of residual in the implantation– Regenerate tissue

• Desirable properties are- greater hydrophilicity- greater reactivity- greater porosity

Most widely used

Polylactide (PLA), Polyglycolide (PGA), Poly(glycolide-co-lactide) (PGLA)

ApplicationsTissue screws, suture anchores, cartilage repair Drug-delivery system

Biocompatibility of biomaterials

• The ability of a material to elicit an appropriate biological response in a specific application without producing a toxic, injurious, or immunological response in living tissue– Strongly determined by primary chemical structure

• When an object is incorporated into the body without any immune responses it is said to be BIOCOMPATIBLE

Standardization of Biomaterials FDA (united states food and drug administration) Biocompatibility tests• acute systemic toxicity………denoting the part of

circulatory system• Cytotoxicity…….toxic in living cell• Haemolysis….dissolution of erythrocytes in blood• Intravenous toxicity• Mutagenesis….permanent genetic alteration• Oral toxicity• Pyrogenicity….products produced by heat• Sensitization…making abnormally sensitive

Guidance on biocompatibility assessment

Material characterization• Chemical structure of material• Degradation products• Residue level Toxicological data• Biological tests based on clinical trial

Guidance on biocompatibility assessment

Supporting documents • Details of application…shape, size, form,

contact time etc.• Chemical breakdown of all materials involved

in the product• A review of all toxicity data• Prior use and details of effects• Toxicity standard tests• Final assessment including toxicological

significance

Types of biomaterials based on surgical uses

Muscular skeletal system…joints in

upper & lower extremities & artificial limbs

Permanent implants

Cardiovascular system …valve, pacemaker, arteries, veins

Digestive system…tooth filling, oesophagus, bile duct

Nervous system…. Dura, hydrocephalus shunt

Cosmetic implants…..nose, ear, teeth, eye

Types of biomaterials based on surgical uses

Transient implants

Extracorporeal assumption of organ function….heart, lung , kidney

Orthopaedic fixation devices….screw, hip pins, bone plates, suture, surgical

adhesives

External dressings & partial implants….artificial skin, immersion

fluids

Aids to diagnosis….catheters, probes

Performance of Biomaterials

• Fracture• Loosening• Infection• Wear

r = 1-f

r is reliability of implant

f is failure

Future challenges

• To more closely replicate complex tissue architecture and arrangement in vitro.

• To better understand extracellular and intracellular modulators of cell function.

• To develop novel materials and processing techniques that are compatible with biological interfaces

• To find better strategies for immune acceptance

Biodegradable

• Natural polymers

Polyhydroxyalkanoates (PHA)

Cellulose composites/membranes

Polylactide acid (PLA)/Starch blends• Synthetic polymers

Polyesters

Polyvinyl alcohol

Polycaprolactone

How to read a paper

• What is research paradigm?...............field with current state

• What is particular problem area?• What is author’s thesis & argument?• What was strategic plan in experimental?• Does the paper succeed?• How the work should be followed up on?