Preparation Of Fluorescent Cefminox Sodium Carbon Nanodots And Their Application In The Treatment And Detection Of Bloodstream Infections

Objective:Using the antibiotic cefminox sodium as the only precursor,different cefminox sodium carbon nanodots(CS-CDs)were obtained by microwave-assisted method under different microwave power.The physicochemical properties and structural composition of the CS-CDs were studied,and their antibacterial activities and applications were explored in order to obtain nano-drugs with fluorescence sensing function and excellent antibacterial activity.Methods:1.Preparation of cefminox sodium carbon nanodots:Using cefminox sodium powder as carbon source,the reaction concentration was 1 mg/m L,and the reaction time was 10 min.By controlling the reaction power(360 W,540 W,720 W and 900 W)as the only variable,different CS-CDs solutions were obtained by microwave assisted method.The solution was coarse filtered by 0.22μm microporous filter membrane,then centrifuged and purified by ultrafiltration tube to obtain yellowish CS-CDs solution.2.Property analysis of cefminox sodium carbon nanodots:transmission electron microscopy(TEM),UV-visible absorption spectroscopy(UV-vis),fluorescence spectroscopy(FL),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and other methods were used to conduct physicochemical property analysis and structural characterization of CS-CDs.3.Experimental study on cefminox sodium carbon nanodots in vitro:Antibacterial activity of CS-CDs in vitro was evaluated by antibacterial plate and antibacterial curve.The drug resistance of E.coli to CS-CDs was evaluated by drug resistance experiment.The specific situation of E.coli destruction was observed by TEM.The cytotoxicity of CS-CDs on mouse embryonic osteoblasts(MC3T3-E1),human normal liver cells(LO2)and human embryonic kidney cells was studied by Cell Counting Kit-8 method.4.In vivo experimental study of cefminox sodium carbon nanodots:A mouse model of acute E.coli bloodstream infections was established to evaluate the antibacterial activity of CS-CDs in vivo.The mice successfully selected for modeling were randomly divided into three groups:Model group,CS group and CS-CDs group.The changes of body temperature,white blood cell count and the number of E.coli in each group were recorded.;The pathological changes of major organs of mice were detected by HE staining;ELISA method was used to detect the expression level of IL-6 in the serum of mice,and to explore the therapeutic effect of CS-CDs on bloodstream infections of E.coli.At the same time,the biological safety of CS-CDs was investigated with healthy normal mice.5.Fluorescence sensitivity of cefminox sodium carbon nanodots for quantitative detection of E.coli:Mice anticoagulant blood was mixed with cefminox sodium carbon nanodots solution and a series of increasing concentrations of E.coli suspensions(0.5×10~6,2.0×10~6,5.0×10~6,1.0×10~7,1.0×10~8,2.0×10~8,5.0×10~8and 1.0×10~9CFU/m L)were co-incubated in indoor environment for 6 h.The number of E.coli bacteria in the blood was detected by the sensitive change of its fluorescence intensity.Results:1.Cefminox sodium carbon nanodots solution is yellow,with a diameter of1.44±0.34 nm and strong blue-green fluorescence.As the reaction power increases,the color of the solution gradually darkens.Under the irradiation of 365 nm UV light,they all emit blue-green fluorescence.2.The characterization of physicochemical properties proved that theβ-lactam ring(a quaternary ring with large tension and poor stability)was hydrolysis during the microwave reaction.However,due to the relatively mild reaction conditions,many of the sodium structures are still retained in the carbon nanodot system.3.In vitro bioactivity studies have proved that CS-CDs can effectively inhibit the growth and reproduction of E.coli,and has low biotoxicity to MC3T3-E1,LO2 and HEK293T cells,and reduce the drug resistance of E.coli..4.By summarizing and analyzing the above results,the optimal reaction power of CS-CDs is 540 W.Compared with model group and CS group,CS-CDs could effectively treat E.coli bloodstream infections in mice when the CS-CDs solution was injected into mouse tail vein.Moreover,the toxic side effects of CS-CDs were low and did not cause damage to the body of healthy mice.5.The results showed that based on the fluorescence sensing characteristics,after co-incubation of CS-CDs solution with blood containing E.coli in a short time(6 h),the concentration of bacteria in blood could be quantitatively detected by detecting the fluorescence intensity of the mixed solution system(CS-CDs solution,blood and bacteria).Conclusion:Using the antibiotic cefminox sodium as the only precursor,cefminox sodium carbon nanodots were synthesized by one-step microwave method.The prepared cefminox sodium carbon nanodots are relatively uniform in size,good in water solubility,and show obvious fluorescence activation dependent characteristics.Cefminox sodium carbon nanodots showed low biotoxicity and good antibacterial activity in vitro and in vivo.Cefminox sodium carbon nanodots can effectively treat acute bloodstream infections in mice with little stimulation to biological organisms.In addition,the sensitive change of fluorescence intensity of cefminox sodium carbon nanodots enables it to rapidly and quantitatively detect the number of bacteria in blood while effectively treating acute bloodstream infections,providing a new idea and way for clinical treatment of bloodstream infections and effective monitoring of infections degree of patients with bloodstream infections.