Screening Of Tumor-targeting Peptides Based On Cell Membrane Chromatography And In Vivo Tumor Inhibition Of Bacteroid Liposomes

At present,cancer is still the second largest disease threatening human health.Poor specific targeting and poor permeability in tumor tissues are two problems faced by nano-drug delivery systems.Traditional theory believed that nanomedicine can be enriched in tumors through the EPR effect,but the latest research shows that the actual enrichment rate achieved by the EPR effect is only about 0.7%.Therefore,it is necessary to find more efficient tumor-targeting substances.There are many types of tumor-targeting materials.Peptides,as one type of tumor-targeting substances,have many advantages such as high specificity,good biocompatibility,small molecular weight,and easy synthesis.So they have been receiving extensive attention and research.Cell membrane chromatography is often applied to the extraction of active pharmaceutical ingredients since its establishment because of its simple and effective screening mechanism.Based on its simple and effective screening mechanism,our research improved the traditional synthesis method of cell membrane chromatography,and established a tumor-targeting peptide screening technology based on cell membrane chromatography-like method.This method relies on the principle that the target substance can specifically bind to the cell membrane surface receptor to screen the target peptide sequence.In this study,sol-gel method was used to synthesize Si O₂ microspheres with a particle size of about 2?m,and the photosensitivity of diazo resin was used to realize the covalent bond connection between the cell membrane and the silica ball carrier material,so that the cell membrane was not easy to fall off and strengthened.The stability of the stationary phase is fast and environmentally friendly compared to other preparation methods.A large number of random peptide libraries were synthesized by solid-phase synthesis,and the synthesized peptide library was simply and quickly screened by solid-phase extraction,and the peptide sequences retained on the cell membrane surface were sequenced and were further verified the targeting ability,then targeting peptides were obtained.This method is convenient and simple,and can quickly obtain the target peptide sequence of relevant cancer cells in a short time,eliminating the tedious operation process of other methods,and is of great significance for the screening of anti-cancer targeting peptides and antibacterial peptides.In recent years,tumor-associated macrophages(TAMs)have been found to promote tumor growth,metastasis and spread by secreting special cytokines and growth factors,and occupy a large proportion in the tumor tissue stroma.With the characteristics of easy deformation and abundant numbers,TAMs have become a new direction for anti-tumor nanocarriers.Mycobacterium tuberculosis in the cell could resist the acidic environment inside the phagosome,prevent the phagosome from fusing with lysosome,and stay in the cell for a long time,eventually destroying the cell.Based on the above,we embed the fragments of Mycobacterium tuberculosis into the nano-scale liposomes to prepare a bacteroid-like liposome.This liposome could follow the macrophages to penetrate deep into the tumor and destroy the TAMs.The possibility of verifying the structure and function at the cellular level has been previously verified.This research further supplements the material characterization of the structure and its anti-tumor performance in vivo.We prepared bacteroide-like liposome with a particle size of about 80 nm by the liquid membrane method,and the load rate of the bacilli fragments was calculated to be 10.23%by the fluorescent labeling method.Through the low loading rate,we made the material have the ability to inhibit the digestion of macrophages,so that it can exist in the macrophages stably for a long time.Through this method,the prepared system can not only follow the macrophages to migrate to the depth of the tumor,but also destroy the macrophages,thereby destroying the microenvironment on which the tumor depends.This system achieves the goal of killing two birds with one stone.We put forward a new idea for tumor targeting carrier to avoid the immune system,and it also proposes a new direction for anti-tumor strategies.