Surface Modification Of Black Phosphorus Nanosheets For Photodynamic Killing Of Bacteria

Photodynamic therapy（PDT）is a new type of therapy that treats cancer and bacterial infections by irradiating a photosensitizer with a specific wavelength of laser to produce active oxygen.PDT has the advantages of high controllability,less trauma,low toxicity,and no obvious toxicity.However,PDT depends on the oxygen levels in the lesion to produce sufficient active oxygen,and prolonged light exposure would cause tissue hypoxia.In addition,most photosensitizers are hydrophobic,and their solubility in the body fluid is not high and their bioavailability is low.Therefore,it is clinically important to improve the biocompatibility of photosensitizers and enhance the efficiency of PDT.In the current study we used black phosphorus as photosensitizer.After the black phosphorus crystals were broken by ultrasounication,black phosphorus nanosheets（BP）with a size of 200-300nm were obtained.The 2-pyridone-based diazo compound（APy-Da）was covalently conjugated on BP to obtain BP@APy,and the further deposition of platinum nanoparticles onto BP@APy yielded the modified product BP@APy-Pt.The H₂O₂ in the bacterial infection site is catalyzed by Pt nanoparticles to generate additional O₂ to enhance the PDT efficiency under light irridiation.2-Hydroxyketone was used to store ¹O₂ generated during the light irridiation,and then slowly released ¹O₂ in the subsequent dark environment to achieve continuous treatment.A dissolved oxygen analyzer was used to detect the oxygen concentrations in the solution,indicating that BP@APy-Pt had an excellent ability to catalyze the generation of O₂ by H₂O₂.Using 1,3-diphenylisobenzofuran（DPBF）as a ¹O₂ probe indicated BP@APy-Pt had an excellent ability to produce ¹O₂,and could continuously release¹O₂ within 24 hours after 20 minutes of light irridiation.The in vitro antibacterial experiments showed that after 20 minutes of laser irradiation,BP@APy-Pt had excellent antibacterial ability,and the inhibition rates of Staphylococcus aureus and Pseudomonas aeruginosa growth reached more than 99%.In a animal model of bacterial infection wounds,BP@APy-Pt could effectively kill bacteria at the infected site and promoted the wound healing rates.This study demonstrates a new strategy to develop BP-based antibacterial agents.