natural biomaterials

Natural BiomaterialsPresented By:-

Anup Neupane (B1)Pragya Dhungel (B6)

andPranish Pradhan (B7)

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Biomaterial• A biomaterial is a nonviable material used in a medical device intended to interact with biological systems. (Williams 1987)

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Classes of Biomaterials• Metals• Polymers• Hydrogels• Bioresorbable and

Bioerodible material

• Ceramics, glasses and glass ceramics

•Natural Materials•Composites•Thin films, Grafts and coatings•Fabrics•Biologically functional materials

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Natural Biomaterials

• The natural biomaterials group includes naturally occurring biomaterials and chemical modifications of these materials.

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•Advantages• Biomimetic,• More

biocompatibility,• Capability of

designing biomaterials which function at molecular level,

• Controlled degradation

•Disadvantages• More

immunogenic• Structural

complexity• Mostly degraded

by natural enzymes

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Some Natural Biomaterials

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Polysaccharide• Carbohydrates with more than 10

monosaccharides units.• General uses : Wound healing Drug delivery

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Polysaccharide as biomaterial

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• Long chain linked sugar molecules.• Mainly found in plants.• Promotes bone regeneration.

Cellulose

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Amylose•A spiral polymer made up of D-glucose units.

•Sustained drug release

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Dextran• Expressed by bacteria (leuconostoc

mesenteroide),• Highly soluble and investigated as

blood plasma replacement (1940s),• Resists protein adsorption

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Chitin• Hydrophobic,• Derived mostly from exoskeleton of

Arthropods• N-deacetylated derivative- CHITOSAN• Wound healing, drug delivery, tissue

engineering scaffolds

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Glycosaminoglycans

• Occur naturally as a polysaccharide branches of protein chain to which they are covalently attached by oligosaccharide link.

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• Hyaluronan-promote angiogenesis and wound healing• Chondrotin Sulphate-adhesive for sealing corneal incision• Heparin-anticoagulant

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Polynucleotides• Repeating chain of nucleotide units • RNA and DNA• Detection of damage to cell caused

by biomaterials

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Protein• Long chain of amino acids linked by

peptide bonds,• Contains 20amino acids ,

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Structure of protein• Primary Structure

• Linear sequence of amino acids linked by peptide bonds

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Secondary Structure • Consists of α-helix and β-pleated

sheets

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Tertiary and Quaternary Structure

• The final arrangement of domains in the polypeptide

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Proteins as Biomaterials

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Silk• Natural protein fibre, mainly

composed of fibrinogen• Produced by larvae of

mulberry silkworm Bombyx mori• Mostly in beta conformation• Uses: Sutures, Scaffolds

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Keratin• Found in dermal parts, nails, hairs

etc.• 100% α-helix.• 18% Cys residue.• Nano fibrous mat for wound healing.

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Gelatin• Solubilized amorphous collagen,• Sustained drug delivery,• Bioadhesive .

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Fibrinogen• In blood.• Synthesized by hepatocytes in liver.• Guides better cellular behaviour.• Scaffolds.

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Elastin• Extensively interconnected, rubbery

network that can stretch and bend in any direction when stressed, giving connective tissue elasticity .

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Collagen

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Collagen • Main structural protein.• Most abundant,25%-35% of total

body protein.• Major part of ECM.• May be found as gel(Vitreous

humor),tight bundle of fibres(Tendon),angled fibres(Bone).

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Structure • Triple helix.• Mostly contains Glycine and Proline.• Both have their own importance.

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Structure Contd…• Glycine present in

every 3rd position.

• -Gly-X-Y sequence where:- X=Pro(mostly)

Y=Hyp or Hyl(mostly)

• Triple helix stabilized by H-bonds.

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Collagen Disorders• By mutation which

causes the deformation of structure.

• Ehlers-Danlos Syndrome:-

— Stretchy skin.• Osteogenesis

Imperfecta:—Bones that easily bend

and fracture.—Known as Brittle Bone

Syndrome.

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Types

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Properties of CollagenMechanical Properties:-

• Stiffness=1000MPa

• Ultimate Tensile Strength=100MPa

• Young’s Modulus=2.9GPa

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Electrical properties:-• Electrically neutral.

• Piezoelectric in nature.

• Electrostatic state changes with changing pH.

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Biological Properties:-• Collagen-Platelets interaction.

• Collagen-Immune system interaction.

• Collagen in cell differentiation. Forms morphogenetic templates. Mediates intercellular flow of

information.

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Isolation and PurificationCollection of collagenous tissues.• Eg:-Rat tail, Bovine Achilles tendon,

etc.

Dissolution of tissues.1. With salt:-• Gives salt soluble fraction of

collagen.• Treated with 0.5M Na2HPO4 .• Ultracentrifuged and obtained in

supernatant.

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Isolation and Purification 2. With acid:- Tendons + 0.5M Acetic acid 0.05M EDTA 48-96hrs pH=2.5-3.0

Acid soluble fraction

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Isolation and Purification3. Enzymatic isolation:-

• Same as acidic isolation.

• BUT, also pepsin 0.05g per 100g tissue.

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Isolation and PurificationPurification:-• By dialyzation vs. different

concentration of Na2HPO4 .• 0.01M for salt soluble; 0.05M for acid

soluble;0.02M for collagen isolated enzymatically.

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Extraction of Collagen from Rat Tail:-Dissolution in acetic acid

Mixing and Lyophilization

Mixing with acetic acid

1.Centrifugation

2.Degassing

3.Sterilization

1%NaOH

pH=6.5-7

pH=3.5

Collagen Gel

Characterization• Protein Amount Determination:-

Indirectly from the amount of hydroxyproline.

• Viscosity Measurement:- By Cannon-Fenske viscometer.

• SDS-PAGE:- Technique for separating biological macromolecules according to their electrophoretic motility.

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References• http://www.jungsanbiomed.com/• http://www.columbia.edu/• http://www.nature.com/• http://www.mdpi.com/• http://www.jbc.org/• http://www.woodwisdom.net/• www.books.google.com• Ratner Buddy D., Et .al Biomaterial Science:An

Introduction to Materials in Medicine.• Lippincott’s Biochemistry.• Lehninger’s Biochemistry

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