Surface and morphology of spray-dried pegylated PLA microspheres

Abstract

The morphology, the surface structure, and the mean diameter of spray-dried biodegradable pegylated microspheres were studied by X-ray photoelectron spectroscopy (XPS) technique, scanning electron microscopy (SEM) and photo correlation spectroscopy. PEG 400-distearate (PEG-400(C 18) 2) was incorporated into poly( d, l-lactic acid) (PLA) by spray-drying using different concentrations of PLA and polyethylene glycol-distearate (PEG-distearate). The use of these different concentrations resulted in systems with different sizes, morphologies and surfaces. Microsphere characteristics such as size distribution, morphology, and PEG distribution were investigated and proven to be highly dependent on the concentrations of PLA and PEG in the solutions to be spray-dried. Scanning electron microscopy showed that the PLA concentration in the polymeric solution rise to microparticles rather than microspheres. Red blood cell-like structures were observed for a high PLA concentration. Photocorrelation spectroscopy proved that the size distribution depended on the initial viscosity of the polymeric solution. The more viscous was the solution, the bigger the microspheres (and vice versa). X-ray photoelectron spectroscopy confirmed the assumption that greater is the amount of PEG-distearate in the formulation, the more it is found on the surface. These results have allowed us to predict pegylated biodegradable microspheres to be the best microencapsulation process.