Synthesis Of Tellurium/Cefotaxime Nanomaterials And Their Effects On Resistance To Drug-Resistant Bacteria Under LED/NIR Light

As antibiotics have been used in clinic frequently and irraditonally,the problem of antibiotic resistance bacteria is increasingly highlighted,which makes traditional antibiotics lose their antibacterial efficacy.Restoring the suspectibility of ineffective antibiotics to drug-resistant bacteria is an optional strategy to combate the problem.Our group has found that bismuth telluride(Bi2Te3)or telluride dioxide(Te O2)combined with β-lactam antibiotic cefotaxime(CTX)showed synergistic effect against Methicillin-resistant Staphylococcus aureus(MRSA),respectively,and telluride played a key role in the synergistic action.Meanwhile,tellurium possesses strong photothermal conversion ability,which can effectively improve the antibacterial activity through the photothermal effect.Based on discovery,we synthesized tellurium-cefotaxime(TeCTX)nanomaterial and investigated its antimicrobial activities against two kinds of clinically related common drug-resistant bacteria MRSA and drug-resistant Escherichia coli(DREC)by using light-emitting diode(LED)and near infrared(NIR)light irradiation,and further studied the antimicrobial mechanism and wound healing ability of mice.The major research works were listed as following:1.Synthesis and characterization of Te-CTX nanocomposite.Te-CTX was synthesized in aqueous phase by using bovine serum albumin(BSA)as dispersant,fructose as reducing agent and stabilizer.Component,morphology and size of synthesized materials were characterized by X-ray powder diffraction(XRD),dynamic light scattering(DLS)and transmission electron microscopy(TEM).The content and valence states of tellurium in Te-CTX nanocomposites were determined by X-ray photoelectron spectroscopy(XPS)and inductively coupled plasma mass spectrometry(ICP-MS).The existence and content of CTX were determined by Fourier infrared spectrometer(FTIR)and thermogravimetric analyzer(TGA).The results showed that the synthesized samples were petal-like Te-CTX nanocomposite with good dispersion and stability with particle size of about 40 nm,and the content of CTX was about 23%.2.Study on antibacterial activity,mechanism and mouse epidermal wound healing of Te-CTX under LED light.The inhibition rate against MRSA reached 93.71% after 8 h treatment by 100 μg/m L of Te-CTX.LED can enhance the antibacterial ability of TeCTX in a short time.The inhibition rate of 25 μg/m L of Te-CTX against MRSA and DREC reached 88.79% and 99.99% respectively after 5 min of LED illumination.Through measuring temperature,glutathione content and observing bacterial morphology,it was found that Te-CTX produced strong photothermal effect,cause bacterial structure destruction and decreased glutathione content under LED light,which leading bacterial death.Cytotoxicity and hemolysis experiments showed that TeCTX had low toxicity against NIH3T3 cell and hemolysis.The results of mice wounds experiments showed that Te-CTX significant accelerated MRSA-infected the healing of wounds under LED light,in the meantime had less potential toxicity.3.Study on the antibacterial activity and mechanism of Te-CTX nanocomposite under NIR light.NIR enhanced the antibacterial ability of Te-CTX in a short time.The inhibition rate of 25 μg/m L Te-CTX against MRSA and DREC reached 99.72% and 99.60% respectively after 10 min of NIR illumination.The results of temperature measurement,bacterial morphology and intracellular reactive oxygen species(ROS)content determination,it showed that Te-CTX produced strong photothermal effect,bacterial structure destruction and intracellular ROS increasement under LED light,which lead to death of bacteria.