The biocompatibility of fluorescent nanodiamonds and their mechanism of cellularuptake

Abstract

The labeling of cells with fluorescent nanoparticles is promising for various biomedicalapplications. The objective of this study is to evaluate the biocompatibility and themechanism of the cellular uptake of fluorescent nanodiamonds (FNDs) in cancer cells(HeLa) and pre-adipocytes (3T3-L1). With flow cytometry and the use of a battery ofmetabolic and cytoskeletal inhibitors, we found that the mechanism of the FND uptake inboth cells is by energy-dependent clathrin-mediated endocytosis. In addition, the surfacecharge of FND influences its cellular uptake, as the uptake of poly-L-lysine-coated FNDs isbetter than that of oxidative-acid-purified FNDs at the same concentration in regularmedium with or without serum. We also confirm that the proliferative potential ofFND-treated and untreated cells does not exhibit any significant differences when measuredat bulk cultures, and more stringently at clonal cell density. Further biocompatibilitystudies indicate that the in vitro differentiation of 3T3-L1 pre-adipocytes and 489-2osteoprogenitors is not affected by the FND treatment. Our results show that FNDs arebiocompatible and ideal candidates for potential applications in human stem cell research.