Strategies For Protein Fiber Degradation And Cellular Oxidative Damage Based On Photodynamic Therapy

The principle of photodynamic therapy(PDT)is activating the photosensitizer produces reactive oxygen species(ROS)through selective illumination of the lesion.ROS has strong oxidizing properties,short half-life and small diffusion range.It can precisely control the production of ROS through the design of photosensitizer structure to achieve precise damage to the target;ROS produced by photosensitizer entering diseased cells can affect cell structure,causeing irreversible oxidative damage.Therefore,ROS can not only degrade inducing disease proteins,but also damage diseased cells to achieve precise treatment of diseases.This thesis focuses on the following three aspects.One is to design and synthesize thymine(T)modified zinc phthalocyanine(ZnPc)to combine with the metal ions that induce AD protein fibers to form T-ZnPc strong binding capacity and vigorous PDT activity.PDT-based fibrils can be effectively degraded in this microenvironment.The second is to design a bionic red blood cell nano-oxygen diagnosis and treatment system to relieve solid tumors'hypoxia and realize high-efficiency PDT treatment of solid tumors.The third is to design and synthesize L-arginine ethyl ester modified ZnPc(Arg-ZnPc),combining nitric oxide(NO)gas with PDT to achieve efficient tumor synergistic therapy.The above-mentioned studies prove that PDT has great application potential in various diseases.The research results of the thesis provide a new structure,new ideas and new methods for the application of PDT in various diseases.The specific research content is as follows:1.The protein fiber degradation for mitigating Alzheimer's disease based on PDTThe aggregation of amyloid substances in the brain to form amyloid plaques,that is,the formation and aggregation of A?peptide fibrils is a typical pathological feature of Alzheimer's disease(AD).There are abnormally high levels of Cu²⁺,Zn²⁺,Fe³⁺,and Al³⁺in the nerve fibers of AD patients,and these ions are involved in the toxic reaction of fibril polypeptide formation.The research in this paper found that thymine-modified ZnPc photosensitizer(T-ZnPc)can specifically bind Fe³⁺or Al³⁺to form Fe-T-ZnPc or Al-T-ZnPc.The photodegradation mechanism experiments show that the addition of Fe³⁺or Al³⁺can significantly enhance the interaction between T-ZnPc and A?fibrils.After being irradiated by a light source with a specific wavelength of 665 nm,T-ZnPc is triggered to generate ROS and degrade A?fibrils.In vitro MTT experiment and cell apoptosis detection showed that the survival rate of T-ZnPc group nerve cells(PC-12)after adding Fe³⁺or Al³⁺was up to 80%,and only 17.46%or 16.76%of the cells had apoptosis,which effectively inhibited the toxicity of A?fibrils.2.Application of biomimetic red blood cells to relive tumor hypoxic in PDT systemHemoglobin(Hb)shows great potential in the field of relieving hypoxia and treating cancer with its unique properties such as good biocompatibility and high oxygen-carrying capacity.Oxyhemoglobin(Oxy Hb)is Hb that is bound to oxygen.The rich histidine residues in its structure have a strong binding ability to Cu.Therefore,the Fe₃O₄@Cu O nanomaterials prepared in this paper are used to adsorb Oxy Hb efficiently.The results of adsorption experiments showed that the maximum adsorption capacity of Oxy Hb is 0.99 mg mg^-1.Adsorb octa-substituted aniline quaternary ammonium salt phthalocyanine(ZnPc)on the periphery and encapsulate hyaluronic acid(HA)to form a BRBC biomimetic nano drug-carrying system.Fe₃O₄ provided active targeting function,Oxy Hb released oxygen to relieve hypoxia,ZnPc played an active role in killing tumor cells.HA provided the drug-carrying system with stability in blood transmission the ability to target tumor cells passively.In vivo and in vitro activity experiments showed that compared with other administration groups,the BRBC+magnetism administration group had the best anti-tumor activity.The multi-mode imaging experiment of BRBC provided strong support for monitoring the tissue distribution of drugs in mice and effective treatment and realized an integrated treatment model of diagnosis and treatment.3.NO gas and PDT synergistic treatment systemThe gas signal molecule nitric oxide(NO)plays a critical regulatory role in various physiological and pathological activities of cells.According to reports in the literature,low concentrations of NO(10^-12-10^-9 M)can be stored in cell growth,and high concentrations of NO(>1?M)can promote cell death.NO has an extremely short half-life and is easily converted into the form of nitrite during blood transmission.How to control the release of NO during cancer treatment is significant,which depends on the light dose during the PDT process and the treatment time and release of the location of NO.In this paper,we designed and synthesized L-arginine ethyl ester modified ZnPc(Arg-ZnPc).The photosensitizer molecule has a guanidine group that can release NO.When the drug reached the tumor cells,the light was applied to cause ROS and RNS and release NO.Through ROS and RNS detection,fluorescence imaging technology,EPR experiment,protein immunoassay technology,and GSH experiment,it has been proved that NO can form ONOO^-,promote vasodilation,and down-regulate the overexpression of efflux transporter(P-glycoprotein,P-gp)and destroy the intracellular redox balance regulated by GSH.Anti-tumor activity experiments in vivo and in vitro showed that the cell activity and tumor suppression effect of the Arg-ZnPc group was significantly better than that of the lysine ethyl ester modified ZnPc(Lys-ZnPc)group without NO release,which proved the NO gas/PDT combined treatment system can significantly improve the effectiveness of treating tumors.