Biodegradable implants based on photo-cross-linked aliphatic polycarbonates for long-acting contraception

In this study, a new class of biodegradable contraceptive implants was prepared via the UV ir-radiation molding method, among which, progestin levonorgestrel (LNG) was used as a model drug. Photo-cross-linked aliphatic polycarbonates (APCs), namely, poly (trimethylene carbonate-co-2,2'- dimethyltrimethylene carbonate) [P(TMC-co-DTC)] elastomers, were used as the drug delivery matrix. The results obtained from the degradation experiments carried out in Sprague-Dawley (SD) rats showed that the cross-linked elastomer had the degradation characteristics of the surface erosion degradation mecha-nism, with no generation of acid degradation products, and excellent form-stability, which met the per-formance requirements of the matrix for a long-acting sustained-release delivery system. The in vitro cy-totoxicity tests and histological and immunohistochemical evaluations showed good biocompatibility and biosafety of the elastomer matrix material and contraceptive implants. Subsequently, the implant formu-lations were screened by in vitro release experiments, and their release kinetics were explored. Finally, in the evaluation study of the in vivo anti-fertility effect, the implants exhibited excellent dimensional sta-bility and were degraded by a surface erosion mechanism. LNG achieved a stable and sustained release in female SD rats, maintaining a long-acting contraceptive duration of up to 4 months. The contraceptive implants obtained in this study could be used to address the limitations of currently available formula-tions, which required secondary surgical removal and a single means of regulating drug release kinetics. Therefore, these implants could provide a new option for birth control needs and may be of significance in reducing the incidence of induced abortion and protecting female fertility. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.