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, 170–180°C, 70 Pa, and 10 h, the viscosity-average molecular weight (Mη) 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 erythromycin–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 (T1/2) 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 T1/2in 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. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2143–2150, 2004