Supercritical antisolvent precipitation of PHBV microparticles.

The micronization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from organic solutions using supercritical antisolvent (SAS) technique has been successfully achieved. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 3 to 9 microm were obtained. The effect of CO(2) and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a dichloromethane (DCM) solution. The best process conditions for this mixture were, according to our study, 40 degrees C, 100 bar, 1 mL min(-1) liquid flow and 10 L min(-1) carbon dioxide flow. Experiments with polymers containing different HV percentages were carried out. The powders obtained became more spherical as the HV content decreased.

Preparation of controlled release microspheres using supercritical fluid technology for delivery of anti-inflammatory drugs.

Ethylcellulose/methylcellulose blends were produced using different precipitation techniques and impregnated with naproxen, a non-steroidal anti-inflammatory drug (NSAID). Solvent-evaporation technique was used not only for the preparation of ethylcellulose/methylcellulose microspheres but also to encapsulate naproxen. Supercritical fluid (SCF) impregnation was also performed to prepare naproxen loaded microspheres. The microspheres, impregnated by the SCF technique, were prepared both by solvent-evaporation and by a supercritical antisolvent (SAS) process. In vitro release profiles at pH 7.4 and 1.2, of naproxen-loaded microspheres were evaluated and the results were modelled Fick's law of diffusion and Power law. Miscrospheres prepared by supercritical antisolvent have a higher loading capacity and present a slower release profile. The systems studied present a release mechanism controlled by drug diffusion which complies Fick's law of diffusion.