Nanoparticles of poly(D,L-lactide)/methoxy poly(ethylene glycol)-poly(D,L-lactide) blends for controlled release of paclitaxel

Paclitaxel is one of the best antineoplastic drugs found in nature in the past decades, which has excellent therapeutic effects against a wide spectrum of cancers. Because of its high hydrophobicity, Cremophor EL has to be used as adjuvant in its clinical dosage form (Taxol (R)), which has been found to cause serious side effects. Nanoparticles of biodegradable polymers may provide an ideal solution. In this research, paclitaxel-loaded nanoparticles of POIY(D,L-actide)/methoxy poly(ethylene glycol)-polylactide (PLA/MPEG-PLA) blends of various blend ratio 100/0, 75/25, 50/50, 25/75, and 0/100 were formulated by the nanoprecipitation method for controlled release of paclitaxel. It was found that increasing the proportion of MPEG-PLA component in the blend from 0 to 100% resulted in a progressive decrease of the particle size from 230.6 +/- 11.1 nm to 74.8 +/- 14.0 nm. The zeta potential of the drug-loaded nanoparticles was increased accordingly from -19.60 +/- 1.13 mV to a nearly neutral, that is, -0.33 +/- 0.28 mV, which indicates the gradual enrichment of PEG segments on the particle surface. The findings were further confirmed by X-Ray Photoelectron Spectroscopy (XPS) analysis. Differential scanning calorimetry (DSC) analysis showed that the glass transition temperature of PLA was significantly decreased from 58.7 to 52.1 degrees C with an increase of MPEG-PLA proportion from 0 to 75%, suggesting the miscibility of PLA and MPEG-PLA. The pure PLA nanoparticles (100/0) exhibited the slowest drug-release rate with 37.3% encapsulated drug released from the nanoparticles for 14 days while the MPEG-PLA nanoparticles (0/100) achieved the fastest drug release with 95.9% drug release in the same period. (c) 2006 Wiley Periodicals, Inc.