Preparation And Characterization Of Carbon Dots Derived From Three Yunnan Genuine Medicinal Materials

Carbon dots(CDs),as zero-dimensional nanomaterials with good luminescent properties,low toxicity,good biocompatibility and other excellent properties,have been widely used for decades.Due to the large particle size and low solubility,traditional Chinese Medicine(TCM)is difficult to give full role to its medicinal efficacy,though its resources are rich and diverse in China,which limits its applications greatly.It is a challenge to use modern nanomaterials preparation technology to redevelop the traditional Chinese herbal medicine resources.First of all,four kinds of traditional Chinese medicine CDs(TCM-CDs,Pn-CDs,Pn N-CDs,Pk-CDs and Ge-CDs)were prepared by one-step hydrothermal method derived from Panax notoginseng,Polygonatum kingianum and Gastrodia elata,respectively and analyzed in this study.The structure and optical properties of four kinds of TCM-CDs were analyzed by transmission electron microscope(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis)techniques.The results showed that the average size of the four kinds of TCM-CDs are 4-7 nm,molecular spacing is 0.21nm,diffraction peak width is about 21°.They are rich in amino groups,carboxyl groups,hydroxyl groups and carbonyl groups,indicating that they have good water solubility.The biological activity of TCM-CDs was studied in the study too.The bacteriostatic and antioxidant activities of Pn-CDs,Pk-CDs and Ge-CDs were also investigated.The bacteriostatic experiment showed that three kinds of TCM-CDs have both inhibitory effect on Gram-positive(G⁺)and negative(G^-)bacteria,and the MIC of Pk-CDs towards Bacillus cereus was determined as 6.25 mg/m L.It has been proved that TCM-CDs played an antibacterial effect by destroying the formation of cell membrane and inhibiting the synthesis of DNA polymerase by scanning electron microscopy(SEM)and quantitative fluorescence PCR(qRT-PCR)techniques.The scavenging rates of DPPH free radicals of three kinds of TCM-CDs were determined as 3.64,2.99,14.33 mg/m L;and superoxide anion(O^2-·)free radicals were 0.20,0.30,0.18 mg/m L,respectively.The experiment of oxidative damage in aging mice model showed that D-galactose can effectively induce oxidative damage in mice,the middle and high dose treatment of three kinds of TCM-CDs increased the body weight of mice,the levels of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px)level,and decreased the level of malondialdehyde(MDA)in plasma,heart,liver and spleen(p<0.05)significantly,indicating that three kinds of TCM-CDs also have strong antioxidant capacity.The results indicated that the TCM-CDs have certain biological activity,which provides a valuable exploration for the further development of traditional Chinese medicine resource.Finally,the applications of TCM-CDs in biological imaging and environmental pollutant detection were investigated.Among them,the quantum yield of N-doped P.notoginseng CDs(Pn N-CDs)is 18.41%,and the maximum excitation and emission wavelength are deduced to be 348 nm and 437 nm respectively,and it presented the best fluorescence performance,which is suitable for biological imaging.The cell membrane and nuclear membrane of plants and mice can be stained by Pn N-CDs and can be used in the imaging of microorganisms in vivo,due to its good biocompatibility.In addition,the fluorescence of Pn N-CDs can be specifically quenched by Cr⁶⁺,and the linear range is 0 to 6?M(R²=0.996),which has the potential to be used as a detector for Cr⁶⁺effectively.In this paper,three traditional Chinese medicines,P.notoginseng,P.kingianum and G.elata,were used as materials to prepare CDs,and their physicochemical properties and biological activities were explored.The research results provided a new idea for the redevelopment of traditional Chinese medicine resources in future.