Violet Phosphorus Nanodots for Long-Term Cell Imaging With Persistent Intracellular Stability

Long-term cellular imaging probes with high photoluminescence intensity/stability and high biocompatibility are crucial for advanced in vitro cell imaging and long-term cell tracing. However, conventional organic fluorescent dyes are prone to photobleaching and require assistance to enter cells. Here, NH₂-PEG-NH₂ was adopted to modify violet phosphorus quantum dots to obtain PEG-VPNDs with strong and stable photoluminescence, where bond contacts were built between NH₂-PEG-NH₂ and phosphorus through P─N and P─O to keep robust structures. The PEG-VPNDs have been demonstrated to have outstanding photoluminescence stability both in solution and intracellular environments. No photoluminescence decay was observed after 60 days of storage under ambient conditions or after continuous irradiation with a 300 W xenon lamp for 3 h, in contrast to the photobleaching observed in organic fluorescent dyes. The PEG-VPNDs were also demonstrated to easily enter A2780 and SKOV3 cells and stay outside the nucleus without any assistance, where no decay was observed for photoluminescence of PEG-VPNDs even for 96 h. The PEG-VPNDs have been demonstrated to have high viability in A2780 and SKOV3 cells with concentration of 144 ppm. The photoluminescence performance with high intracellular stability and high biocompatibility makes PEG-VPNDs a promising candidate for long-term bioimaging, cell tracing and other biomedical applications.