Direct synthesis of poly(D,L-lactic acid) by melt polycondensation and its application in drug delivery

Starting from D,L-acid and SnCl2 as catalyst, poly(D,L-lactic acid) (PDLLA) was directly synthesized by melt polycondensation. Under the appropriate conditions such as 0.5 wt % SnCl2, 170-180degreesC, 70 Pa, and 10 h, the viscosity-average molecular weight (M-eta) of PDLLA was 4100 Da. PDLLA produced by the most practical method was used as the drug-delivery material for erythromycin and ciprofloxacin. The optimal conditions for the preparation of erytliromycin-poly(D,L-lactic acid)-microsphere (ERY-PDLLA-MS) for lung targeting was investigated, and further confirmed by good reappearance tests. DSC and SEM demonstrated that ERY-PDLLA-MS had good spherical shape. The release in vitro of ERY-PDLLA-MS was effective and the half-time (T-1/2) was 51.0 h. After 175 h, the accumulated release percentage was 80.0%. The test in vivo showed that ERY-PDLLA-MS was more easily distributed in rabbit lung tissue. When PDLLA was applied in an antibacterial ciprofloxacin drug-delivery microsphere (CIP-PDLLA-MS), CIP-PDLLA-MS was also characterized with DSC and SEM, and the release T-1/2 in vitro was 24.9 h. After 53.2 h, the accumulated release percentage reached 84.0%, which indicated that CIP-PDLLA-MS was advantageous to long-term release. (C) 2003 Wiley Periodicals, Inc.