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?