POLYMERIC BIOMATERIALS VASCULAR GRAFTS 1 Biomaterials The normal

POLYMERIC BIOMATERIALS VASCULAR GRAFTS 1

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’’ 2

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 3

Polymeric Biomaterials • Polymers - long chain molecules of high molecular weight [-(CH 2)n- ] n State 1 -4 5 -11 Gas Liquid 9 -16 16 -25 2550 10003000 med. visc. liquid hi visc. solid liq. tough plastic • 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 4

Cardiovascular Disease Proportion of global NCD deaths under the age of 70, by Cause of death, 2008. 5

Normal Coronary Anatomy 6

Coronary Artery Disease (Plaque, Atherosclerosis) 7

What is Heart Attack? • 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. 8

Samples of coronary arteries 9

Treatment Angioplasty & Stent 10

Treatment Coronary Artery Bypass Graft (CABG) Surgery 11

History of Polymer Biomaterial in Artery Prosthesis §late of 1800 s Autologous grafting (veins and arteries). . §Early of 1900 s Synthetic implants become available (PVA, 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 ). 12

Coronary Artery Properties Mechanical Properties Tensile Strength Young Modulus (MPa) ( GPa ) 1. 40– 11. 4 10 ± 3 Elongation 45– 99% 13

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. 14

Polymer Blend Mixing 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. 15

Coronary Artery from present work 16

Thanks 17