Tuning the release rate of acidic degradation products through macromolecular design of caprolactone-based copolymers.

Macromolecular engineering is presented as a tool to control the degradation rate and release rate of acidic degradation products from biomedical polyester ethers. Three different caprolactone/1,5-dioxepan-2-one (CL/DXO) copolymers were synthesized: DXO/CL/DXO triblock, CL/DXO multiblock, and random cross-linked CL/DXO copolymer. The relation of CL and DXO units in all three copolymers was 60/40 mol %. The polymer discs were immersed in phosphate buffer solution at pH 7.4 and 37 degrees C for up to 364 days. After different time periods degradation products were extracted from the buffer solution and analyzed. In addition mass loss, water absorption, molecular weight changes, and changes in thermal properties were determined. The results show that the release rate of acidic degradation products, a possible cause of acidic microclimates and inflammatory responses, is controllable through macromolecular design, i.e., different distribution of the weak linkages in the copolymers.