Construction Of Tumor Acidity-Responsive Nanocarriers And Their Applications In Cancer Therapy

Nanoparticle-based delivery systems can enhance drug solubility,alter tissue distribution,and reduce side effects,and thus play an essential role in the delivery of chemotherapies and immunotherapies.However,nanomedicines face multiple delivery barriers in vivo,such as blood,tumor and cells,which reduce drug delivery efficiency.Limited penetration of nanomedicines in tumor tissues is a crucial factor severely limiting their efficacy.An efficient delivery system should be able to change its performance by adapting to the needs of different delivery stages to improve delivery efficiency.The construction of physiological microenvironment-responsive smart nanomedicines is one of the important strategies to achieve the above goals and overcome barriers of in vivo delivery.In order to solve the problem of insufficient penetration of nanomedicine in tumor tissues,a novel tumor acidic microenvironment-responsive nanomedicine delivery system based on dendritic macromolecules was developed for the in vivo delivery of chemotherapy drugs and immunomodulatory drugs.This dissertation contains three parts:1)the first part develop a novel synessay method of environmentally sensitive PAMAM derivatives using polyamide-amine dendrimers PAMAM and N,N-dialkyl aminoethyl as raw materials,and then verify the temperature and p H response;2)basedd on the method mentioned in the first part,the second part of the dissertation focuses on the construction of tumor acidity-responsive size-shifted nanomedicines delivery system to enhance the penetration of gemcitabine in pancreatic cancer tumor tissues and improve the efficacy of chemo-immunotherapy;3)In the third part of the dissertation,in order to deliver immunomodulatory drugs(R848)to both tumor tissues and lymph nodes,we constructed an R848-bonded tumor acidity-sensitive nanomedicines delivery system to enhance tumor penetration while improving lymph node drug delivery.The specific studies in the three parts of this dissertation are as follows.1.A method for preparing novel environmentally sensitive dendrimer derivatives by facile chemical reactions was established.We obtained a series of structurally graded dendrimer derivatives by bonding different structural N,N-dialkylaminoethyl units to the surface amino groups of PAMAM dendrimers,and systematically investigated the conformational relationship between their structures and properties.It was found that the chemical structure and the number of dialkylaminoethyl units,as well as the polymer concentration,p H and the number of generations of PAMAM can affect the temperature-responsive performance of the dendrimers.Meanwhile,we can obtain dendrimer materials with different p H response ranges by modulating the chemical structure and number of substitutions of dialkylaminoethyl units and PEG.The prepared temperature-sensitive materials and p H-responsive materials can be adjusted in a large range of temperature and p H,such as temperature close to human body and p H of different targeting parts.2.On this part,we focused on the development of a tumor acidity(p H 6.8)responsive size-shifted nanocarrier(SPN)to enhance the penetration of the gemcitabine(Gem)in pancreatic cancer tumor tissues and improve the efficacy of chemo-immunotherapy.The size of the prepared loaded Gem nanodrug(SPN@Pro-Gem)is about 120 nm under neutral conditions,undergoes a size shift from 120 nm to 8 nm under the stimulation of tumor acidity,which significantly promotes drug penetration in deep tissue of tumor.In addition,SPN@Pro-Gem can also upregulate PD-L1 expression in tumor cells.The combination of SPN@Pro-Gem and anti-PD-1 antibody(αPD-1)further improved the therapeutic efficacy of pancreatic cancer.Analysis of tumor immune cells revealed that SPN@Pro-Gem could significantly down-regulate immunosuppressive cells(such as TAMs,MDSCs and Tregs)and promoting CD8~+T cell infiltration in tumor tissues.3.Further studies have found that tumor permeable nanocarriers can improve drug delivery of lymph nodes.Therefore,we further prepared tumor acidity-responsive nanoedicines(SPRN)bonded to the immunomodulatory drug R848 based on the previous SPN carriers.The experimental results showed that the size-shifted SPRN can achieve drug delivery to both tumor tissues and lymph nodes.R848 was delivered to the deep tissue of the tumor through enhanced tumor penetration to perform the function of repolarizing macrophages.At the same time,R848was promoted to penetrate into the tumor lymphatic vessels and migrate to the tumor drainage lymph nodes,so as to activate DC cells in the lymph nodes.In vivo therapeutic experiments have shown that SPRN can increase the infiltration of CD8~+T cells and improve the immunosuppressive microenvironment,thus effectively inhibiting the growth of melanoma and breast cancer tumors.