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POLYMERIC BIOMATERIALS VASCULAR GRAFTS

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Biomaterials

The normal description of a biomaterial is “any substance (other than a drug) or combination of substances, synthetic or natural in origin, which can be used for any period of time, as a whole or as a part of a system which treats, augments, or replaces any tissue, organ, or function of the body’’

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Biomaterials Selection Criteria

• The physicochemical properties

• Biocompatibility

• Mechanical requirements

• The nature of the physiological

environment at the organ/tissue level

• The desired function of the prosthesis

• Cost

Polymeric Biomaterials

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• Polymers - long chain molecules of

high molecular weight [-(CH2)n- ]

• Covalent , H-bonding , Entanglements

• Replacement and augmentation of various soft tissues(vascular grafts , heart valves , artificial hearts, breast implants and contact lenses).

• Polytetrafluoroethylene, and Silicone rubber

n 1-4 5-11 9-16 16-25 25-50

1000-3000

State Gas Liquid med. visc.

liquid

hi visc. liq.

solid tough plastic

Cardiovascular Disease

Proportion of global NCD deaths under the age of 70, by Cause of death, 2008.

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Normal Coronary Anatomy

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Coronary Artery Disease

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(Plaque, Atherosclerosis)

What is Heart Attack?

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• Coronary artery becomes blocked - usually by a clot.

• Blood flow is closed off and a heart attack begins.

• If blockage continues, parts of the heart muscle start to die.

• Heart may stop beating.

Samples of coronary arteries

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Treatment

Angioplasty & Stent

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Treatment

Coronary Artery Bypass Graft (CABG) Surgery

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History of Polymer Biomaterial in Artery Prosthesis

late of 1800s Autologous grafting (veins and arteries). .

Early of 1900s Synthetic implants become available (PVA,PA,PTFE,PE)

1958 PU become available

2005 A multiwalled carbon nanotubes-polyurethane composite (MWNT-PU)

2007 Enhancement of the polyurethane properties, were prepared in various compositions and in medical purity without using any solvent, catalyst or additives.

2009 Fabricated Small diameter vascular grafts from pure Polyurethane (PU), as well as PU reinforced with a weft-knitted tubular fabric(Polyester filament ).

Coronary Artery Properties

Tensile Strength

(MPa)

Young Modulus

( GPa )Elongation

1.40–11.4 10 ± 3 45–99%

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Mechanical Properties

Polyurethane Elastomer

Polyurethanes possess more complex chemical structures that typically comprise three monomers: a diisocyanate, a macroglycol (which is an oligomeric macromonomer) and a chain extender Due to this unique composition, the structure of polyurethanes is quite different from that of other polymers. In fact, PU elastomers usually show a two-phase structure in which hard segment-enriched domains are dispersed in a matrix of soft segments. The hard segment-enriched domains are composed mainly of the diisocyanate and the chain extender, while the soft segment matrix is composed of a sequence of macroglycol moieties.

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Polymer BlendMixing of two or more different polymers together makes it possible to achieve various property combinations of the final material—usually in a more cost-effective way than in the case of synthesis of new polymers.Silicone rubber (SR): is a rubber-like material composed of silicone itself a polymer containing silicon together with carbon, hydrogen, and oxygen.

• biocompatibility• superior chemical resistance.• Good mechanical properties.• low bacterial action and thrombogenicity.

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Coronary Artery from present work

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Thanks

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