POLYMERIC BIOMATERIALS VASCULAR GRAFTS
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’’
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 • 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
Cardiovascular Disease Proportion of global NCD deaths under the age of 70, by Cause of death, 2008.
Coronary Artery Disease (Plaque, Atherosclerosis)
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.
Treatment Angioplasty & Stent
Treatment Coronary Artery Bypass Graft (CABG) Surgery
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 PUbecome 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 FabricatedSmall diameter vascular grafts from pure Polyurethane (PU), as well as PU reinforced with a weft-knitted tubular fabric(Polyester filament ).
Coronary Artery Properties 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.
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.