Long-term in vivo degradation behavior of poly(trimethylene carbonate-co-2, 2'-dimethyltrimethylene carbonate)

Poly(trimethylene carbonate-co-2, 2'-dimethyltrimethylene carbonate) P(TMC-co-DTC) copolymers with different molecular weights or molar ratios were prepared by bulk ring-opening polymerization (ROP) of tri-methylene carbonate (TMC) and 2, 2'-dimethyltrimethylene carbonate (DTC). The in vivo degradation behavior of the resulting copolymers of 2 mm diameter was subsequently investigated by implanting the samples sub-cutaneously in the back of rats. The data showed that the sample's mass loss was reduced, and the form-stability was enhanced with the increase of DTC segments content in the copolymer while increasing the molecular weight could accelerate the degradation rate and improve the form-stability of the copolymers. Among them, the samples containing 25 mol% DTC segments with a molecular weight of 205 kDa achieved the highest mass loss of 26.1% and maintained good form-stability after 35 weeks of implantation. In particular, implants with high DTC segments amount of 75 mol% (molecular weight of 208 kDa) maintained excellent form-stability and a low mass loss of 4.8% during the implantation cycle and exhibited some properties different from the other groups. Further experimental results showed that the content of DTC segments increased from 74.4% to 77.3%, and the crystallinity of the copolymer transformed to semi-crystalline state also increased from 61.4% to 76.4% during the degradation. The T-g, T-m and hardness of the degraded polymers were correspondingly improved. In addition, the degradation mechanism of surface erosion in vivo of the resulting P(TMC-co-DTC) copolymers were verified. This work provides a promising class of candidate carrier materials for the application of long-acting drug delivery systems through a detailed study of the in vivo degradation behavior of P(TMC-co-DTC) copolymers.

Automated summary

This study prepared poly(trimethylene carbonate-co-2, 2'-dimethyltrimethylene carbonate) (P(TMC-co-DTC)) copolymers with different molecular weights or molar ratios and investigated their in vivo degradation behavior through implantation experiments in rats. The results showed that increasing the content of DTC segments in the copolymer reduced mass loss and enhanced form-stability, while increasing the molecular weight accelerated degradation rate and improved form-stability. The study provides promising carrier materials for long-acting drug delivery systems.