Construction And Anti-Tumor Activity Of The Self-Assembled Peptide Polymer Nano-Drug Delivery System Responsive To Endogenous Environment

Nano-drug delivery systems have received widespread attention in tumor treatment due to their advantages in improving drug bioavailability,improving drug delivery efficiency,and reducing drug toxic and side effects.Some drugs have been used clinically,but more carrier systems have stopped in pre-clinical research.The most important reason for this is safety.When nano-drug carrier systems enter the organism,they will gather in different tissues for a long time.If the material is toxic,it will endanger human health.Therefore,the nano-drug carrier system needs to develop in the direction of both functionality and safety.Self-assembling peptides are composed of amino acids and can self-assemble into nanotubes,nanoparticles,nanofibers,nanobelts,etc.They have good biocompatibility,biodegradability.In this study,phenylalanine dipeptide(FF)was used as the self-assembling peptide matrix.Through the modification of FF,the goal is to construct a nano drug-carrying system that is simple to synthesize,has low biological toxicity,has good drug-carrying capacity,and is responsive to the tumor environment.The research was divided into four parts.First,we synthesized a pH-responsive self-assembling peptide polymer(FFPFF).FFPFF was formed by coupling FF and Pluronic F127(F127)through Schiff base bond.It can self-assemble into nanospheres,and has good water solubility,pH responsiveness.FFPFF can be taken up by cells through clathrin and caveolin-mediated endocytosis,then escaped from lysosomal.Cytotoxicity,Caenorhabditis elegans model and hemolysis experiments proved that it has low toxicity and good blood compatibility.The doxorubicin(DOX)drug model proved that FFPFF has a good drug-carrying capacity.The drug in FFPFF released less drug in a neutral environment,but was released quickly in an acidic environment.The ATN-161 peptide is a ligand for the integrin ?5?1 protein.The integrin ?5?1protein is overexpressed on the surface of a variety of tumor cells.Therefore,the modification of the ATN-161 peptide can achieve the targeted delivery.The ATN-161 peptide was modified at both ends of FFPFF,named ATN-FFPFF-ATN.The target cell(MDA-MB-231)proved that ATN-FFPFF-ATN promoted cellular uptake by recognizing the integrin ?5?1 protein.ATN-FFPFF-ATN-DOX significantly inhibited the proliferation of MDA-MB-231 cells,significantly increased the rate of apoptosis,and increased the expression of apoptosis-related protein Caspase 3 in vitro.And the effect was better than FFPFF-DOX(non-targeted control)and DOX(free drug).Polyethylene glycol(PEG)can improve the stability,immunogenicity of the nano-drug delivery system in vivo.And it will prolong the half-life of the drug.We modified the ATN-FFPFF-ATN by PEG.In addition,in order to avoid the restriction of the release of the drug,we used matrix metalloproteinase 9(MMP-9)responsive peptides to link PEG and ATN-FFPFF-ATN.We synthesized a pH,enzyme dual response type self-assembling peptide polymer(PEG-MAF=P).It can target the cells with high expression of integrin ?5?1 protein.And it has good stability in physiological environment.However its structure was fragmented in acid and MMP-9enzyme environment,which can quickly release the drug.PEG-MAF=P-DOX can significantly inhibit tumor cell activity in vitro.At the end,we used tumor-bearing nude mice and SD rats as models,proved that ATN-FFPFF-ATN and PEG-MAF=P can target tumor cells and increase the enrichment of drugs in tumor tissues in vivo.And the anti-tumor effect was significantly better than the same dose of DOX in vivo.In addition ATN-FFPFF-ATN and PEG-MAF=P can alleviate animal weight loss and the normal tissues damage caused by DOX.PEG-MAF=P can significantly increase the absorption of drugs and prolong the average retention time.It has the best anti-tumor effect in the experiment.PEG-MAF=P has good research potential.