Abstract: Objective:To explore the feasibility and efficacy of N-doped silicon quantum dots (N-SiQD) as fluorescent labeling materials for living cells of human umbilical vein endothelial cell (HUVEC). Methods: N-SiQD was characterized by transmission electron microscope and fluorescence spectrophotometer. HUVEC was cultured in vitro, and then co-cultured with different concentrations of N-SiQD. The CCK-8 and Calcein-AM/PI staining were used to evaluate the biosecurity of N-SiQD. Meanwhile, the effects of N-SiQD on tube formation of HUVEC were also observed, and the expression of angiogenesis genes was analyzed. Finally, the fluorescence labeling properties of N-SiQD on HUVEC in vitro was detected by confocal microscopy. Results: The N-SiQD as spherical nanoparticles with superior water-dispersibility was about 4.62 nm, and it showed green fluorescence under 488 nm exciting light. CCK-8 results showed that after 24 h co-incubation, compared with the control group, the activity of N-SiQD groups with a concentration of less than 800 μg/mL showed no statistical significance, while N-SiQD groups with a concentration of more than 1 000 μg/mL showed significant influence on cell proliferation (P<0.05). 400 μg/mL N-SiQD promoted the tube formation of HUVEC, and VEGFA gene expression was increased while VEGFB gene expression decreased, with statistical significance (P<0.05). Confocal microscopy showed that 400 μg/mL N-SiQD distributed well in the cytoplasm and emitted stable green fluorescence. At the excitation wavelength of 488 nm, N-SiQD could maintain about 40% of the initial fluorescence intensity within 30 min. Conclusions:The newly synthesized N-SiQD has good biocompatibility and fluorescence labeling function on living cells, and it may promote the behavioral function of HUVEC at appropriate concentration. Therefore, N-SiQD can be used to label living cells of HUVEC.

Key words: N-doped silicon quantum dot, umbilical vein endothelial cell, living cell labeling, angiogenesis