Release of the fluorescent marker Prodan® from poly(D,L-lactic acid) nanoparticles coated with albumin or polyvinyl alcohol in model digestive fluids (USP XXII)

Abstract

Prodan® release from poly(D,L-lactic acid) (PLA 50) nanoparticles coated with albumin or polyvinyl alcohol (PVA) in simulated gastric and intestinal fluids (USP XXII) was investigated. Prodan® is a fluorescent marker, whose fluorescence properties enabled the concurrent determination of the free and bound compound without prior separation of the nanoparticles. In simulated gastric fluid, where the PLA 50 matrix of both PLA 50 nanoparticle systems coated with albumin or PVA was not degraded, the nanoparticles coated with albumin or PVA showed similar Prodan® release properties: Prodan® release from both nanoparticles coated with either albumin or PVA was shown to follow kinetics consistent with diffusion through the intact polymeric matrix. One hundred percent release was obtained within 120 min. In simulated intestinal fluid, however, the Prodan® release from the PLA 50 nanoparticles was different depending on the agent coating the nanoparticles: when PVA was used as a coating agent, e.g. when no degradation of the PLA 50 matrix was observed, Prodan® was released by diffusion through the intact PLA 50 matrix. Due to its very low affinity for water at this pH, only 44% of Prodan® was released. By contrast, Prodan® release from PLA 50 nanoparticles coated with albumin was driven by both matrix erosion and diffusion processes. Accordingly, 100% release occurred over 480 min, despite the low affinity of Prodan® for the aqueous phase at the pH of the simulated intestinal fluid.