Preliminary Study On Antibacterial Activity Of Red Phosphorous Photocatalyst And The Uptake Rate In Different Tumor Cells

Objective Tumor is one of the serious threats to human life and health.At present,main tumor treatments,including surgery,radiotherapy and chemotherapy,have poor efficiency and are limited by recurrence,chemotherapy resistance and non-specific targeting.Photodynamic therapy（PDT）is a safe and effective cancer treatment based on photosensitizer（PS）and oxygen.The mechanism is that PS absorbs light and molecular oxygen existing in tissues to generate reactive oxygen（ROS）for therapeutic effect.PS as an exogenous substance into the body will be cleared by the immune system.In addition,its own disadvantages such as poor stability,unstable drug release and short blood circulation time also limit the clinical application.PS camouflaged by natural erythrocyte membrane inherits the immune escape ability of natural red blood cells and is a relatively new strategy for drug delivery and tumor treatment assembled by its own biofilm and PS.Therefore,in this study,red phosphorus（RP）based PS with high photocatalytic activity was constructed,and preliminarily explored its enhanced photocatalytic activity by antibiosis experiments.A safer biomimetic system based on natural biofilms and red phosphorus was further built,it possesses better biocompatibility and easier localization and quantification,then its uptake by different types of tumor cells is explored.The study provides a basis for the application of new photosensitizers in tumors.Methods The photosensitizer with high photocatalytic activity was constructed by using RP as activated molecule and titanium oxide nanofiber as substrate.Then,gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were used as model bacteria to evaluate the photocatalytic activity of the PS.The ROS produced during the photocatalytic process was detected by free radical capture method and electron paramagnetic resonance（EPR）.Then the photocatalytic PS was further constructed with carbon nitride（C₃N₄）as the substrate,and the characterization was conducted by scanning electron microscopy,transmission electron microscopy,laser confocal microscopy（CLSM）.The biocompatibility was quantitatively analyzed by scratch experiments and pro-caspase-3proteins,and the uptake of PS by different types of tumor cells was determined by flow cytometry.Finally,erythrocyte membrane of SD rats was covered on the surface of PS with a micro-extruder to construct bionic membrane PS.Particle size and Zeta potential were measured by dynamic light scatterer（DLS）method,and the coverage and co-localization of erythrocyte membrane and PS surface were observed by CLSM.The biocompatibility was further confirmed by hemolysis test and CCK-8 method,and the uptake of the PS by He La cells was determined by flow cytometry in addition.Results（1）Heterostrutured TiO₂@RP PS was successfully constructed.（2）Under white LED irradiation for 25 min and 30 min,the killing rate of 7-log CFU mL^-1 EScherichia coli and Staphylococcus aureus by TiO₂@RP reached up to 100%.After six cycles,the PS still had high photocatalytic activity and stability.（3）The results of radical capture and EPR showed that the concentration of h⁺,^·O₂^ˉand H₂O₂ increased in the photocatalyst PS.The heterojunction interface of RP-based PS could significantly promote the separation and transport of photogenerated charge carriers.（4）A safer and healthier heterostructured photocatalytic PS（C₃N₄@RP）was also successfully constructed.The results of scratch test showed that the PS with the concentration of 50μg mL^-1 had no effect on cell viability.（5）The uptake of PS in human lung adenocarcinoma cells（A549）and cervical tumor cells（He La）was time-dependent,and the uptake of PS was the highest in A549 cells at 4 h and He La cells at 24 h when co-incubated with the PS at a concentration of 20μg mL^-1.The uptake of PS in He La cells was significantly higher than that in A549 cells when the concentration of PS was 20μg mL^-1 and incubated for 24 h.（6）Bionic PS was successfully constructed by using red cell membrane as bionic membrane through simple extrusion process.（7）Hemolysis test and CCK-8 results showed that the biocompatibility of He La cells was significantly improved,and flow cytometry analysis showed that the intake of biomimetic PS was also significantly increased.The bionic PS has a hemolysis rate of only1.2%and can be administered intravenously.CCK-8 assay showed that cell viability was not significantly affected at 100μg mL^-1.Conclusion（1）The PS with heterojunction structure was successfully constructed.Under the visible light irradiation,the PS can produce a large number of ROS and kill 100%pathogenic microorganisms in a short time.The results showed that construction of heterojunction structure is an effective way to improve the photocatalytic performance.（2）Bionic membrane heterojunction PS with high biocompatibility was constructed successfully.The bionic heterojunction PS was beneficial to the uptake of tumor cells due to the appropriate size and the homology of biofilms.This study opens up new ideas for the construction of novel PSs,and lays a foundation for bionic membrane PSs in tumor uptake and further anti-tumor effects.