Preparation And Antibacterial Properties Of Boron Nanosheet Composite Materials

The drug resistance of pathogenic bacteria caused by the abuse of antibiotics makes the development of new antibacterial drugs urgent.As a new kind of two-dimensional nanomaterial,boron nanosheets have large specific surface area,high drug loading and excellent photothermal conversion performance,which has broad prospects in antibacterial field.However,the preparation of boron nanosheets is still facing the problem of difficult stripping.At the same time,the poor dispersion of boron nanosheets in water system also seriously affects the application of boron nanosheets in antibacterial field.Therefore,in this paper,different methods and conditions were explored to prepare ultra-thin boron nanosheets,and a series of boron matrix composites with photothermal and NO controlled release properties were constructed based on boron nanosheets,and their structures and applications in the fields of antibacterial and wound healing were studied.The main results are as follows:(1)Preparation of boron nanosheets(B NSs).Ultrathin two-dimensional boron nanosheets were prepared by microwave hydrothermal method and ultrasound-assisted liquid phase stripping by adding etchants or surfactants.Boron nanosheets with a thickness of about 5 nm and uniform size were successfully prepared by ultrasonic method using surfactants as additives.The highest photothermal conversion efficiency was 22.16%.The best stripping conditions were explored.The results show that the prepared boron nanosheets have good stability.(2)Preparation and properties of chitosan and nitric oxide donor-loaded boron nanosheets(B-QCS-BNN6).Abstract:A composite nano-antibacterial material B-QCS-BNN6 was prepared by modifying the surface of ultra-thin boron nanosheets with positively charged quaternary ammonium chitosan and nitric oxide donor BNN6.The positively charged surface of the nanosheet can effectively improve its stability and water dispersion,and the negatively charged bacteria can be trapped to improve its stability and water dispersion.The loading efficiency of nitric oxide donor BNN6 is about 21%,and the photothermal conversion efficiency of B-QCS-BNN6 nanostructure under 808 nm laser irradiation is up to 22.03%.The temperature rise caused by infrared laser irradiation could promote the controlled release of nitric oxide,and the effective killing rate of E.coli and S.aureus model bacteria reached 99.9%.Moreover,the combined effect of PTT and NO could significantly accelerate the healing of MRSA infected wounds by enhancing the reepithelization of wound tissue,increasing collagen deposition and promoting neovascularization.(3)Preparation and properties of boron nanosheet composite hydrogel(GPB-BNN6).BNN6 functionalized boron nanosheets were grafted into methacrylate modified Gel MA hydrogel using mercapto polyethylene glycol.The GPB hydrogels containing 10% Gel MA had a compressive strength of 83.56 kpa,and the boron nanosheets significantly affected the swelling rate and degradation rate of the composite hydrogels.Under the irradiation of 808 nm laser,the GPB-BNN6 hydrogel with boron nanosheet content of 1‰ could reach the high temperature of 68.1℃ for ten minutes,and promoted the directional and controlled release of nitric oxide.The effective killing rate of E.coli and S.aureus was up to 99.9%,showing better biocompatibility.The combination of GPB-BNN6 nanoplates-mediated PTT and NO significantly accelerated the healing of MRSA infected acute wounds by enhancing wound tissue reepithelialization,increasing collagen deposition and promoting neovascularization.