Study On Photodynamic Antitumor Activity Of Phthalocyanine Based On Structural Modification And High Temperature Assisted Enhancement

Cancer is a serious threat to human life and health,and it is still very challenging to seek safe and effective tumor treatment methods.Photodynamic therapy（PDT）is an emerging treatment method that is widely used clinically for the treatment of superficial lesions such as skin diseases.Photosensitizer（PS）,oxygen（O₂）,and light are the three elements of PDT.PDT achieves tumor treatment by producing reactive oxygen species（ROS）to kill tumor cells.PDT has the advantages of high selectivity,minimal invasiveness,and common side effects.However,in the clinical application of PDT,its effect is still limited by problems such as insufficient activity,hypoxia of solid tumors,and insufficient light source tissue penetration depth.Singlet oxygen（¹O₂）is the most important ROS in the PDT process,but its short life span leads to low utilization rate;classical photosensitizers are activated by visible light,resulting in PDT being limited to the treatment of superficial lesions;tumor hypoxia microenvironment also significantly limits the therapeutic effect of PDT;besides,it is difficult for a single PDT therapy to achieve a good therapeutic effect.In order to solve the problems mentioned above faced by PDT and effectively improve the efficacy of PDT,this paper has carried out the following research:1.Study on synthesis,anti-tumor activity and mechanism of multifunctional phthalocyanineThe penetration depth of the light source that stimulates PS is insufficient.The utilization rate of ¹O₂ produced by the photosensitizer is low.The upregulation of HIF-1αunder hypoxic conditions will produce resistance to PDT are the three major bottlenecks in the PDT treatment process.In this study,we designed and synthesized a multi-functional 2-pyridone-modified tetra-substituted zinc phthalocyanine（Zn Pc-PYR）.The research results show that this phthalocyanine effectively kills three birds with one stone during PDT treatment.Firstly,Zn Pc-PYR can be excited by 665 and 808nm light to generate reactive oxygen species,thereby improving PDT therapy’s therapeutic effect on deep tumor lesions.Zn Pc-PYR can generate ¹O₂ under the excitation of 665 nm and 808 nm light.It can be slowly released after being stored by the pyridone structure to improve the utilization of ¹O₂;finally,Zn Pc-PYR can significantly reduce HIF-1αin tumor cells and enhance tumor sensitivity cells to PDT treatment under hypoxic conditions.While dealing with the tumor microenvironment’s hypoxia characteristics,we have realized the combined treatment of deep and superficial tumors to achieve high-efficiency PDT treatment of solid tumors.Simultaneously,it promotes the release of Ca²⁺from the extracellular or endoplasmic reticulum calcium storehouse to the cytoplasm,forming a positive feedback effect and aggravating cell damage.2.Moderate high temperature can enhance the anti-tumor activity of PDT and the involved mechanism studyWhen PDT is used as a monotherapy,it often fails to achieve a satisfactory therapeutic effect.Therefore,finding a simple and efficient method to improve the therapeutic effect of PDT is of great significance for the development of the clinical application of PDT.Relevant studies have shown that abnormally increased cytoplasmic Ca²⁺concentration can induce mitochondrial and endoplasmic reticulum oxidative stress and generate many ROS to damage cells.The TRPV1 channel on the tumor cell surface is a temperature-responsive Ca²⁺channel,which opens at a temperature greater than 43°C to initiate extracellular Ca²⁺influx.Tumor hyperthermia usually requires heating the tumor temperature to above 45°C and maintaining it for a long time to get significant tumor ablation,which will inevitably cause damage to the surrounding normal tissues.The mild high-temperature conditions of 43～45°C will not cause effective killing of tumor cells but can open the TRPV1 channel and initiate Ca²⁺influx.In this study,we chose a mild high-temperature condition（44°C）in combination with PDT.The study results showed that when cervical cancer He La cells were incubated at 44°C for 20 minutes,the intracellular Ca²⁺concentration was significantly increased,thereby promoting endogenous ROS production in cells.PDT can also generate a large amount of ROS and realize the mutual promotion effect of ROS and Ca²⁺.In vivo and in vitro experiments show that the combination of mild high-temperature conditions and PDT therapy can significantly improve the anti-tumor therapeutic effect of PDT.