Degradation of poly(D,L-lactic acid) nanoparticles coated with albumin in model digestive fluids (USP XXII)

Entirely biodegradable poly(D,L-lactic acid) (PLA(50)) nanoparticles coated with albumin were prepared by the solvent evaporation technique. Their degradative properties were investigated in simulated gastric and intestinal fluids (USP XXII). The degradation of the albumin coating was monitored by HPLC, whereas PLA(50) degradation was determined by size exclusion chromatography (SEC) as well as by the detection of lactate in bulk solution by enzymatic assay. As expected, the coating effect of albumin, a readily digestible protein, rapidly disappeared in both gastric and intestinal media, thus exposing albumin-free PLA(50) cores to hydrolytic processes. In pepsin-rich simulated gastric fluid, no degradation of the PLA(50) core was observed over 8 h incubation time. In contrast, in pancreatin-rich simulated intestinal fluid, the PLA(50) nanoparticles were rapidly converted into lactate. The results showed that the PLA(50) degradation was mainly due to an enzymatic cleavage process. Further experiments showed the involvement of lipases in the degradation of the PLA(50) core in simulated intestinal fluid.