No abstract

To develop an appropriate drug carrier for drug delivery systems, we prepared random poly(lactide-co-glycolide-co-ε-caprolactone) (PLGC) copolymers in comparison to commercial poly(lactic acid-co-glycolic acid) (PLGA) grades.

Thermogelling block copolymers are central to a variety of biomedical applications. Here, we examined the thermal phase transition behavior of the MPEG-b-PCL diblock copolymer (MC) with carboxyl (MC-COOH) and amine (MC-NH 2 ) groups, and their salt forms (MC-COO À Na + and MC-NH 3 + Cl À ) at the chain ends of the PCL segment. All MC copolymers formed an opaque emulsion sol at room temperature when prepared as 20 wt% aqueous solutions. As the temperature increased from room temperature, a sol-to-gel transition was observed for MC, MC-COOH, and MC-NH 2 copolymers, although not for their salt forms (MC-COO À Na + and MC-NH 3 + Cl À ). Introduction of a carboxyl and an amine group into the PCL segment decreased the crystallinity and hydrophobicity of the PCL block domains, which altered the onset temperature of gelation (the gel temperature range) and the maximum viscosity. We confirmed that the sol-to-gel phase transition behavior, which indicated the formation and destruction of a structured gel network of MC copolymers, depended on the crystallinity and hydrophobicity of the PCL domains in aqueous media.

The bare metal stent (BMS) used in the blood vessel caused the restenosis after the operation due to formation and proliferation of neointimal. Recently, as a method to overcome the problems of BMS, drug eluting stent (DES) is developed and being applied to human body which has drug reducing restenosis applied on the metal surface. DES has the advantage of greatly reducing the restenosis after the operation; however, metal stent remains in the body after the drug is released causing issues such as late thrombosis and restenosis so that currently the attention is increasing for biodegradable materials that reduce restenosis and thrombosis by degrading as a certain amount of time passes after the drug is released by the stent material. In this review, the study trend of biodegradable stent will be explained.