Poly(trimethylene carbonate) and monomethoxy poly(ethylene glycol)-block-poly(trimethylene carbonate) nanoparticles for the controlled release of dexamethasone

In this study, single emulsion and salting out methods were employed to prepare poly(trimethylene carbonate) (PTMC) and monomethoxy poly (ethylene glycol)-block-poly(trimethylene carbonate) (mPEG-PTMC) nanoparticles. Well-defined nanoparticles of a PTMC homopolymer were prepared using poly(vinyl alcohol) (PVA) as a stabilizer. The average size of the nanoparticles can be adjusted by varying the stirring speed and polymer concentration. These particles can be readily freeze-dried and redispersed, with little influence on the average particle size and size distribution. Nanoparticles based on amphiphilic mPEG-PTMC can be prepared without an additional stabilizer. In this case, the size of the obtained nanoparticles did not vary much and ranged between 95 and 120 nm. These nanoparticles could be freeze-dried and redispersed as well. Using the salting out method, dexamethasone was loaded into PTMC and mPEG-PTMC nanoparticles at a highest efficiency of respectively 54% and 88%. With the single emulsion method, the loading efficiencies were, respectively, 91% and 72%. These drug-loaded particles were stable in time for at least 20 weeks. It was found that the release of dexamethasone from these nanoparticles was diffusion-controlled and could be sustained for 14 to 60 days. Depending on the nature of the polymer employed and the preparation method, dexamethasone diffusion coefficients varied between 4.8 x 10(-18) and 22.6 x 10(-18) cm(2)/s. (c) 2005 Elsevier B.V. All fights reserved.