Preparation of medical implants by stereolithography

Abstract

In this thesis photo-crosslinked networks and structures have been prepared by stereolithography and evaluated with regard to their applicability for medical implants. Five issues have been addressed. First the degradation characteristics of photo-crosslinked polymer networks were investigated. Networks were prepared from three-armed PTMC macromers (PTMC-tMA) with different molecular weights and co-polymeric macromers of TMC with either Ɛ-Cl or DLLA of the highest molecular weight. The networks were compared on their degradation in vitro and in vivo. It was shown that network density and macromer composition could be used to tailor the degradation rates and properties. Then, the applicability of resins based on macromers with a relatively high molecular weight in stereolithography was explored. Macromers with molecular weights higher than 20 kg/mol were used to prepare processable resins. Designed structures were then built and characterized. Furthermore, a porous meniscus implant with properties close to those of the human meniscus was designed and prepared. The toughness of PTMC networks prepared from mixtures of high and low molecular weight macromer mixtures was investigated. It was shown that such mixtures resulted in networks with mechanical properties close to those of networks prepared from macromers with very high molecular weights. Hydrogel networks prepared from a combination of relatively low molecular weight macromers were assessed. The phase separation of these networks was investigated. Remarkably, these hydrogels networks could be evaluated in tensile and tearing experiments. Designed structures could readily be prepared by stereolithography. Finally, the applicability of (methoxy)-poly(ethylene glycol) grafted layers as lubricants on photo-crosslinked PTMC was evaluated. Grafting resulted in networks with significantly decreased friction coefficients.