Degradation of ZnGa2O4:Cr3+ luminescent nanoparticles in lysosomal-like medium

The ultimate goal of in vivo imaging is to provide safe tools to probe the inside of a body in order to obtain pathological information, monitor activities, and examine disease progression or regression. In this context zinc gallate doped with chromium III (ZGO) nanoparticles with persistent luminescence properties have been previously developed, their biodistribution was evaluated, as well as their in vitro toxicity. However, to date, nothing is known about their potential transformations in biological media, which may hinder their biomedical applications. In order to know if these nanoparticles could degrade, the present work consist in studying their fate over time depending on both their coating and the aqueous media in which they are dispersed. ZGO nanoparticles have been dispersed in three different aqueous solutions and characterized by numerous technics, up to 90 days. Among the evaluated dispersion media, the Artificial Lysosomal Fluid (ALF) mimicking intracellular lysosome environment elicited significant degradation of ZGO nanoparticles. The chelating agents present in ALF have proven to play a major role in the degradation of the ZGO, by stabilizing the nanoparticles and increasing the contact. An important time decrease of the luminescence properties has also been observed, that correlated with the release of ions from ZGO nanoparticles as well as their decreasing size. This information is valuable since it indicates, for the first time, the long-term degradation of persistent luminescent nanoprobes in an in vivo like model medium. Therefore, a possible elimination of the imaging probes after in vivo preclinical applications could be envisioned.