ELECTROSTATIC CHARGE AND PARTICLE-SIZE ANALYSIS OF POLY (D,L-LACTIDE-CO-GLYCOLIDE) MICROSPHERES FORMULATED FOR DRY POWDER AEROSOLS

Electrostatic charge and aerodynamic size distributions analysis were performed using an Electrical-Single Particle Aerodynamic Relaxation T ime (E-SPART) Analyzer in formulation screening of dry powders for use in aerosol delivery to the lung. The respirable fraction (RF) of drug s delivered by dry powder inhalers (DPIs) can be improved more effecti vely by using hydrophobic microspheres as carriers. Poly (D,L-lactide- co-glycolide) microspheres (PLGA) prepared in the respirable size rang e (3-7 mu m) were treated with polyamino acids and isopropanol in orde r to obtain particles of surface charge suitable for use in DPIs. The powder formulations were evaluated for their degree of aggregation by cascade impaction following delivery by the Pfeiffer(R) DPI. The IPA t reated PLGA microspheres had a significantly higher RF (12.9%) as comp ared to the PL and PGA treated microspheres (3.3 and 2.4%, respectivel y), and untreated microspheres (3.8%). Results of electrostatic charge determined by E-SPART analysis suggested that the higher RF for the I PA formulation may be due to its inter-particle repulsive forces cause d by the unipolar charge (+56.3 mu C/g) distribution of the powder.