In-vitro degradation of PLGA nanoparticles in aqueous medium and in stem cell cultures by monitoring the cargo fluorescence spectrum

The hydrolytic degradation of poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles loaded with bovine serum albumin (BSA) covalently labelled with a fluorescent dye (FITC) was investigated spectrally resolving the fluorescence signals. Studies have been conducted in-vitro in phosphate buffer saline and in human adult bone marrow-mesenchymal stem cell cultures. We demonstrated that PLGA nanoparticles degraded in heterogeneous manner and a particle agglomeration process occurs after 21 days of incubation owing to particle fragmentation and leading to cargo release. Additionally, we showed that degradation of up-taken FITC-BSA-PLGA nanoparticles by stem cells may be monitored by the emission spectrum of the released FITC-BSA that shifted towards shorter wavelengths and becomes narrower, after 230 h. Moreover, the changes of fluorescence spectra revealed that the loaded protein is released in the cells during polymer degradation.