Effect Of Antibacterial Activity Based On The Photothermal Effect Of Mussel Shell Melanin On Wound Healing Of Drug-resistant Staphylococcus Aureus Infection

Bacterial infection has become one of the most difficult problems due to antibiotic abuse and subsequent production of antibiotic-resistant bacteria.The development of a new type of antibacterial method that is safe,efficient and resistant to drug resistance is currently a hot research direction.Photothermal therapy is a method in which photothermal agents convert light energy into heat energy to kill bacteria.This noninvasive method does not produce bacterial resistance and is a new antibacterial technology with good application prospects.The key to photothermal treatment is the selection of photothermal agents.It is of great significance to explore new types of photothermal agents with good photothermal conversion properties,especially biocompatible and environmentally friendly antibacterial materials.It is tried to extract and purify natural melanin from mussel shells in Rizhao seawater by two different methods,acid hydrolysis and enzymatic hydrolysis in the article.They were characterized by uv-vis absorption spectrum,Fourier infrared spectrum,scanning electron microscope and X-ray photoelectron spectroscopy,and the method of trypsin hydrolysis was more gentle and the extraction rate was higher.In order to investigate whether melanin can be used as a photothermal agent or not,we performed a photothermal conversion experiment.We found that trypsin-hydrolyzed natural melanin had a better photothermal conversion than HCl hydrolyzed,which made it have a higher antibacterial effect.The rate provides a theoretical basis,and subsequent in vitro antibacterial experiments also verified this.No matter for resistant E.coli or S.aureus,trypsin hydrolyzed-melanin had a higher antibacterial rate.In vitro antibacterial effect based on mussel shell melanin,we further explored its activity in promoting wound healing in rats.The results showed that melanin obtained by trypsin hydrolyzed can inhibit the proliferation of bacteria on the surface of the wound and promote the healing of wounds infected with drug-resistant bacteria under the irradiation of near-infrared laser(808 nm,2W).In terms of biological toxicity,both in vitro cytotoxicity tests and in vivo organ and blood toxicity tests,both melanins have shown excellent biocompatibility.In summary,we used mussel shells as raw materials,through a new type of natural melanin extraction and purification process,to obtain melanin with high light-to-heat conversion rate and excellent antibacterial activity,and through animal experiments to verify its activity to promote wound healing,provides a new idea for the development of natural antibacterial agents using high-value marine resources.