Based On Gold Nanoparticle System With Responsive Aggregation For The Thermotherapy Of Antibacterial

For the current treatment of bacterial infections,the widespread use and even abuse of antibiotics has caused multi-drug resistance in most pathogens,posing a serious challenge to the health and safety aspects of animal husbandry and veterinary,and facing to and solving this problem has become what people are paying attention to now.In this paper,a gold nanoparticle-assisted photothermal therapy material system is used for antibacterial research,based on the good photothermal conversion ability of gold nanoparticles,it can reduce the toxic side effect of traditional drugs and solve the non-targeting of traditional photothermal.Such as the problem,as far as possible to limit the drug in the local area,and does not damage the surrounding normal cells and tissues,etc.,thereby improving the antibacterial effect without any resistance.Although a variety of bactericidal nanoparticles have been reported in the literature,the vast majority of it are used in modern medicine,reports in the field of animal husbandry and veterinary medicine are very rare,indeedly.This paper aims to study the controllable gold nanoparticle-assisted photothermal antibacterial in order to kill pathogenic bacteria,completely.In this study,we successfully constructed an environmental responsive gold nanoparticle antibacterial system(GNPs system).This intelligent system adds environmental responsiveness,based on the increase of photothermal antibacterial effect,hoping to achieve antibacterial fixed-point treatment.First,we used gold nanoparticles as research objects to design peptide-modified gold nanoparticles in order to improve their therapeutic effects and reduce their side effects.Through particle size,transmission electron microscopy and ultraviolet absorption and other tests,the results show that when the p H is reduced from 7.4 to 6.5,the particle size and UV absorption of GNPs-PEG2000 are unchanged basically,and the scattered non-aggregated state is observed under electron microscope,while particle size of the GNPs system can be increased to about 1000 nm,and its UV absorption decreases gradually with time goes on,it shows agglomerated state under electron microscope.The results show that the GNPs system has good p H environmental responsiveness,that is,it can responsive aggregation occurs according to changes in the p H of environment.Furtherly,the photothermal characteristics were also explored.The results show that under the same conditions,at 100 ?g/m L,compared with GNPs-PEG2000,the maximum temperature of GNPs system can reach nearly 70°C,and the temperature difference can reach 50°C,with good photothermal conversion performance.Then,GNPs system was applied to 3T3 and L929 cells respectively,and the lower cytotoxicity was tested by MTT assay.The survival rate of both cells was greater than 85% under the relatively large concentration of 200 ?g/m L.At 200 ?g/m L after routine blood tests,the hemolysis rate was 3.15%,it less than 5%,which proved to have good blood compatibility.For various bacteria,such as Staphylococcus aureus(canine),Staphylococcus aureus(chicken),Pasteurella(porcine),Haemophilus parasuis(porcine),Streptococcus(porcine),Escherichia coli(chicken),bio-luminous Staphylococcus aureus(S.aureur.Xen36),UV-absorbing test results show that GNPs system has a certain antibacterial effect on Gram-positive bacteria and Gram-negative bacteria.At the same time,Escherichia coli(chicken)and S.aureur.Xen36 were screened for the experimental strains of this study.After fluorescent staining and bacterial coating test,the results were consistent with the previous.At last,In order to study the antibacterial effect of GNPs system in vivo,we successfully constructed subcutaneous inflammation models of S.aureur.Xen36 and E.coli(chicken)animals.The results of in vivo heating test showed that GNPs system has a good heating effect at 808 nm NIR laser.Under irradiation,the local temperature rise can reach above 50°C.By observing the body weight and the pathological sections of the main organs,the results showed that the GNPs system did not pose a toxic threat to the animal body,and the biosafety was good.In order to study the antibacterial effect,we analyzed the changes in the area of inflammation for the two inflammatory models.The results showed that under the 808 nm NIR laser irradiation,the inflammation site after GNPs system treatment was already Basically healed in the S.aureur.Xen36 group,the luminous intensity decreased to 0.0023%,and the luminous area decreased to 1.6785%,which was significantly different from other control groups.Similarly,for the E.coli group,the area of inflammation decreased to 11.36674%,compared with the other control groups,and the results were consistent with the previous.This study provides a reference for the clinical application of gold nanoparticles,and provides new ideas for the treatment of inflammation in the field of animal husbandry and veterinary medicine.