Poly(butylene-co-ε-caprolactone carbonate) (PBCL) was synthesized by anionic coordination polymerization of carbon dioxide, 1,2-butylene oxide and ε-caprolactone (CL). PBCL microspheres containing pazufloxacian mesilate were elaborated by solvent evaporation method based on the formation of double W/O/W emulsion. The resulting polymers were characterized by FTIR, ¹H NMR, ¹³C NMR, DSC, TGA and WAXD measurements, and the degradability of polymers and the properties of drug-loaded polymeric microspheres were studied. The results showed that the thermal properties and degradability of poly(butylene carbonate) (PBC) were improved via introduction of CL during copolymerization. The polymeric microspheres had smooth and spherical surface, and the size of most microspheres was in the range of 0.5～1 μm. The drug loading and drug encapsulation efficiency of PBCL microspheres were 38.21% and 87.9%, respectively. In vitro drug release of these microspheres was performed in a pH 7.4 phosphate-buffered solution. The drug released from PBCL microspheres was found to reach 84.74% after 21 d, and that of PBC microspheres was just 17.29%. The re-lease profile obeyed the Higuchi equation. It was suggested that PBCL was suitable for long-term sustained-release drug delivery system.

Key words: poly(butylene-co-ε-caprolactone carbonate), pazufloxacian mesilate, degradable microsphere, sustained release