In-vitro analysis and animal experimental implantation of surface-modifiedbiodegradable polylactide ureteric stents

With the objective of developing a biodegradable ureteric stent, various po lylactides were analyzed and grafted with a clinically adapted surface. Ste nt moulding was performed by CESP technology (Controlled Expansion of Satur ated Polymers),which is not based on high temperature but gas-loading under high pressure which induces a foamy bulk structure. The hydrolytically bio degradable, synthetic homo- and copolymers poly(D,L-lactide) (PDLLA), poly( D,L-lactide-co-trimethylene-carbonate) (PDLLA-coTMC), poly(D,L-lactide-co-g lycolide) (PDLLA-co-Gly) as derivatives of lactic acid or glycolic acid and surface modifications with hydroxyethylene-methacrylate (HEMA) and oligoet hyleneoxidemonomethacrylate (OEOMA) were analyzed with regard to cytotoxici ty and cell adhesion. Methacrylates have minimized protein and cell adhesio n and degradation of non-toxic products. All polymers exhibited a high degr ee of biocompatibility and cell adhesion was markedly reduced foil owing HE MA grafting. A 3 cm and 7 Charriere prototype of the stent was moulded from PDLLA-co-TMC by CESP-technology, and grafted with HEMA by means of plasma- induced polymerization. Finally,the stents were implanted into female sheep , following unilateral ureterotomy. Regular blood and urine analysis as wel l as ultrasound and the final autopsy revealed no pathological findings. Hi stopathological analysis exhibited a regular epithelium without any changes being determined by contact to the stent, and a good regeneration of all l ayers in the area of anastomosis.