Objective: To synthesize the zinc gluconate carbon dots (Zn-CDs) by one-step hydrothermal method, and to investigate their effects on the cell imaging and inducing osteoblastic differentiation of preosteoblasts in the mice. Methods: The Zn-CDs were synthesized by one-step hydrothermal method, and the characteristics were observed and detected by transmission electron microscope (TEM), Fourier transform-infrared spectrum (FT-IR) and fluorescence spectrometer. The MC3T3-E1 cells were divided into blank control group and experimental groups; different concentrations (0.01, 0.10, 1.00, 10.00, 100.00, 1 000 mg middot; L-1) of Zn-CDs were added into the cells in experimental groups, and nothing was added into the cells in blank control group. MTT assay was used to determin the relative growth rate (RGR) of MC3T3-E1 cells in various groups; the imaging characteristics of MC3T3-E1 cells were observed under confocal microscope; the relative expression levels of Runt-relateed transcription factor-2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OC) mRNA in the MC3T3-E1 cells in various groups were detected by qRT-PCR; the number of calcified nodules was detected by alizarin red staining. Results: The TEM results showed that the particle size of Zn-CDs was about 5. 25 nm. The fluorescence spectrometer results showed that the Zn-CDs had the fluorescence properties of 360 nm ultraviolet excited light and 450 nm blue emission light, and the Zn-CDs showed the characteristics of excitation wavelength dependence. The FT-IR results showed that the surface of Zn-CDs was mainly composed of carboxyl groups and hydroxyl groups. Compared with blank control group, the RGR of MC3T3-E1 cells in 1 000. 00 mg middot; L-1 Zn-CDs group was decreased significantly at 24 h after co-culture (P<0. 01). The results of fluorescence imaging showed that the blue, green and red fluorescence in the MC3T3-E1 cells, the outline was clear, and the fluorescence intensity of the cytoplasm was stronger than that of the nucleus after co-cultured with Zn-CDs. The qRT-PCR results showed that the relative expression levels of Runx2, ALP and OC mRNA were significantly increased with the increasing of Zn-CDs concentration. The alizarin red staining results showed that the number of calcium deposits in the MC3T3-E1 cells in different concentrations of Zn-CDs groups were more than that in blank control group after induced for 21 d. Conclusion: Zn-CDs can effectively perform the fluorescence imaging in the MC3T3-E1 cells, and Zn-CDs have a certain ability to promote the osteoblastic differentiation of the MC3T3-E1 cells.
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