Construction Of Two-dimensional Ti₃C₂@Porphyridium Nanocomposite System And Its Application In Photodynamic Therapy Of Hypoxic Tumors

In recent years,Photodynamic therapy（PDT）has attracted much attention due to its advantages of good controllability,minimally invasive,high efficiency and inducing antitumor immune response.However,due to the abnormal proliferation of the vascular system in solid tumor tissues,normal blood circulation cannot be formed,and solid tumors often form a specific microenvironment of hypoxia,acidity,and nutrient deficiency,which greatly weakens the effect of PDT.At the same time,rapid oxygen consumption and vascular injury caused by incomplete PDT can further aggravate hypoxia in tumor tissue and seriously reduce the effect of repeated treatment.Therefore,it is of great significance to design and prepare a PDT system that can provide oxygen for tumor in situ.In this paper,we prepared 2D Ti₃C₂@Porphyridium by simple electrostatic adsorption between ultrasonic stripped photosensitizer two-dimensional Ti₃C₂ and Porphyridium with photosynthesis.During PDT,660 nm light stimulation can trigger Porphyridium oxygen production and PDT treatment simultaneously.At the same time,the oxygen produced by Porphyridium can receive the energy transferred by the excited photosensitizer to produce singlet oxygen,which enhances the efficacy of PDT.The main research contents of this paper include four parts:Part one:Preliminary study of porphyridium.In order to select suitable marine microalgae for scientific research,we measured the photosynthetic oxygen production performance of porphyridium with the photosynthetic oxygen production performance of Chlorella as a control.The measurement results of the dissolved oxygen meter showed that under the same test conditions,after 30 minutes of illumination,the oxygen production of porphyridium was 4.5 times that of Chlorella.In addition,a large number of literatures have also reported that extracellular polysaccharide synthesized by porphyridium has the function of inhibiting tumor cell growth.The above results show that porphyridium has excellent photosynthetic oxygen production performance and can be used as an"oxygen generator"to provide oxygen source for subsequent PDT.Part two:Synthesis and preliminary performance test of 2D Ti₃C₂@Porphyridium.In order to select an appropriate concentration of 2D Ti₃C₂ for compounding with porphyridium,the PDT singlet oxygen production was firstly measured for 2D Ti₃C₂materials with different concentrations.The results show that the PDT singlet oxygen yield of 2D Ti₃C₂ is the highest when the concentration is 10 ppm.The surface potential of 2D Ti₃C₂ was modified by PDDA,and then 2D Ti₃C₂ was adsorbed on Porphyridium by simple electrostatic adsorption.The test results of dynamic light scattering（DLS）instrument showed that the potential of the composite component was obviously between2D Ti₃C₂ and porphyridium,indicating that 2D Ti₃C₂@Porphyridium was successfully prepared.Through the PDT reactive oxygen fluorescence detection of the composite material,it was found that the photodynamic reactive oxygen species production of the composite material was significantly higher than that of 2D Ti₃C₂ at the same concentration.The above results indicate that Porphyridium can provide an oxygen source for 2D Ti₃C₂ under the same laser irradiation and enhance the PDT activity.Part three:Cytological evaluation of 2D Ti₃C₂@Porphyridium.The antitumor activity and cytocompatibility of 2D Ti₃C₂@Porphyridium in vitro PDT were investigated using MCF-7 cells as a model.The phototoxicity test under the condition of cell hypoxia/normoxic treatment and the fluorescence staining test of live/dead cells proved that 2D Ti₃C₂@Porphyridium had good killing performance on MCF-7 cells and its performance was significantly better than that of single PDT treatment.At the same time,the cell dark toxicity test results show that even when the concentration of 2D Ti₃C₂@Porphyridium reaches 100 ppm,the cell viability can still reach more than 80%,indicating that 2D Ti₃C₂@Porphyridium has good cytocompatibility.Part four:Evaluation of 2D Ti₃C₂@Porphyridium photodynamic therapy in vivo.To explore the in vivo photodynamic therapy efficacy and biocompatibility of 2D Ti₃C₂@Porphyridium.The in situ breast cancer tumor model of mice was established,and2D Ti₃C₂@Porphyridium was intervened by intratumoral injection,and laser irradiation was performed every two days for 30 minutes.The body weight and tumor volume of mice were regularly recorded.Finally,the mice were dissected,and their hearts,livers,spleens,lungs and kidneys were taken for H&E staining analysis.The experimental results showed that 2D Ti₃C₂@Porphyridium had obvious inhibitory effect on tumor growth and high biosafety.In order to solve the bottleneck of photodynamic therapy caused by tumor hypoxia,in this paper,porphyridium of the super-strong photosynthetic oxygen-producing performance and the ultrasonically exfoliated photosensitizer 2D Ti₃C₂ were successfully combined by electrostatic self-assembly.The performance test results of 2D Ti₃C₂@porphyridium showed that under the irradiation of 660 nm laser,porphyridium could provide a continuous source of oxygen for photosensitizer 2D Ti₃C₂ through photosynthetic oxygen production,which significantly improved the PDT effect and inhibited tumor growth.