Preparation and subsequent degradation of poly(L-lactic acid) microspheres suitable for aerosolisation: A physico-chemical study

The encapsulation of nedocromil sodium and beclomethasone dipropionate with microspheres of poly(L-lactic acid) has been studied and preparation conditions optimised for entrapment efficiency and microsphere size suitable for inhalation. DSC was used to characterise the microspheres both in terms of drug/polymer interaction and influence of annealing conditions on the T-g and degree of crystallinity. The absence of molecular interaction was confirmed by FTIR. Incubation of the microspheres in phosphate buffer at 37 degrees C for 8 days demonstrated no chemical degradation of the polymer as evidenced by IR spectral analysis and estimates of percentage crystallinity. Surface morphology (SEM) and internal structure (TEM) were consistent with a homogeneous degradation pattern. (C) 1997 Elsevier Science B.V.