[In vitro analysis and animal experiment study of surface modified biodegradable polylactide ureteral stents]. / In-vitro-Analytik und tierexperimentelle Untersuchung oberflächenmodifizierter biodegradierbarer Polylactidureterstents.

With the objective of developing a biodegradable ureteric stent, various polylactides were analyzed and grafted with a clinically adapted surface. Stent moulding was performed by CESP technology (Controlled Expansion of Saturated Polymers), which is not based on high temperature but gas-loading under high pressure which induces a foamy bulk structure. The hydrolytically biodegradable, synthetic homo- and copolymers poly(D,L-lactide) (PDLLA), poly(D,L-lactide-co-trimethylene-carbonate) (PDLLA-co-TMC), poly(D,L-lactide-co-glycolide) (PDLLA-co-Gly) as derivatives of lactic acid or glycolic acid and surface modifications with hydroxyethylene-methacrylate (HEMA) and oligoethyleneoxidemonomethacrylate (OEOMA) were analyzed with regard to cytotoxicity and cell adhesion. Methacrylates have minimized protein and cell adhesion and degradation of non-toxic products. All polymers exhibited a high degree of biocompatibility and cell adhesion was markedly reduced following HEMA grafting. A 3 cm and 7 Charrière 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 well as ultrasound and the final autopsy revealed no pathological findings. Histopathological analysis exhibited a regular epithelium without any changes being determined by contact to the stent, and a good regeneration of all layers in the area of anastomosis.

Biocompatibility, cell adhesion, and degradation of surface-modified biodegradable polymers designed for the upper urinary tract.

OBJECTIVES: The aim of this study was to develop a short bioresorbable ureteric stent and to characterize polymers and their surface modifications with respect to biocompatibility, degradation kinetics, cell adhesion properties, and incorporation of biologically active substances. Poly(D,L-lactide) PDLLA, poly(D,L-lactide-co-glycolide) PDLLA-co-GLY, and poly(D,L-lactide-co-trimethylenecarbonate) PDLLA-co-TMC were chosen as basic polymers. Surface modification was performed by plasma-induced graft polymerization and included grafting with hydroxyethylmethacrylate (HEMA), oligo(ethyleneoxide)-monomethacrylate (OEOMA), and acrylic acid (AAC). Biocompatibility of the polymers was assessed in vitro applying parameters of cell morphology, proliferative activity, and cell adhesion. All polymers were biocompatible and exerted no toxic effect on urothelial cell lines and on primary human urothelial cell cultures. A markedly reduced cell adhesion could be achieved in polymers grafted with HEMA, OEOMA, and AAC. Our results indicate that surface modification of bioresorbable polymers by grafting with HEMA, OEOMA, or AAC is an efficient approach to improve surface properties with respect to biocompatibility and cell adhesion properties.

Development of a biodegradable ureteric stent: surface modification and in vitro assessment.

The aim of the present study was to develop a short bioresorbable ureteric stent and to characterize the chosen polymers with respect to surface modification, biocompatibility, and loading of a biologically active compound. As materials for the stent, poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) were chosen. Degradation experiments were carried out and analytical data were obtained by contact angle measurement, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy in the attenuated reflection mode (FTIR-ATR). Gas loading technology was used to incorporate biologically active compounds, and biocompatibility of the polymers was assessed by in vitro cellular assays, applying measures such as cell morphology, proliferative activity, and membrane integrity. Our results indicate that surface modification of bioresorbable polymers is a suitable and efficient approach to improve the surface properties. Incorporation of biologically active compounds was possible without loss of activity, and in vitro assessment of cellular responses demonstrated the biocompatibility of the chosen polymers and modifications.