Principles of manufacturing biocompatible and biostable polymer implants (review)

Abstract

The review concerns the basic theoretical aspects of manufacturing biocompatible and biostable implants and represents, mainly, the experience of our research team. Biocompatible implants have been shown to be understood to mean both: those, which are not rejected by the body as well as those, which are not capsulated in the body. They are to be fabricated according to one-stage frontal photopolymerization with extreme low reaction front to avoid defect formation in a polymer. Moreover, an additional unstable stage is required to result in the death of end free macroradicals and labile products in a polymer. For implant fabrication we used photopolimerizable compositions resulting in the formation of hydrophobic spatially cross-linked polymers, their correlation time of spinning motion of a paramagnetic probe of 2,2,6,6-tetramethyl-4- oxypiperidine-1-oxide approximately being 6·10–10 s. The fulfillment of these conditions means the use of radically polymerizable oligomerbased compositions (oligoester methacrylates, oligocarbonate methacrylates, oligourethane methacrylates, etc.). Compositions having lower or higher correlation time of the specified probe are not appropriate for the fabrication of biocompatible and biostable implants. The characteristics of oligomer-monomer compounds have a greater effect on physicochemical properties of implants rather than on their biocompatibility and biostability. No implant incapsulation is determined by the initial composition formulation provided that the mentioned conditions are fulfilled. A polymer in biostable and biocompatible implants can be only optically transparent, though the converse is not necessary.