AEROSOLIZED AQUEOUS SUSPENSIONS OF POLY(L-LACTIC ACID) MICROSPHERES

A method is described for the preparation of microspheres of poly(L-la ctic acid) possessing suitable characteristics for aerosolization. Mic roscopic analysis of the sample revealed a median projected area diame ter of 4.2 mum, with a geometric standard deviation of 1.7. Electrical resistance particle size analysis showed that approx. 1% of the popul ation had a size > 12.1 mum, and only 16.6% exceeded 5.5 mum. Scanning electron micrographs show well formed, round and smooth microspheres. Jet nebulization of an aqueous suspension produced a mass output of 4 4.4% of the microspheres over a period of 30 min. Aerodynamic particle size measurement showed that 51.2%, by number (approx. 16.9%, by volu me) of the aerosol generated was < 2.1 mum in diameter. Greater than 8 0%, by volume, of the aerosol was smaller than 5.8 mum in aerodynamic diameter.