Preparation And Characterization Of Amphipathic Intelligent Antitumor Prodrugs Based On Combined Chemo-immunotherapy

As a new cancer treatment method,immunotherapy can activate autoimmune cells(such as macrophages,etc.)to attack cancer cells.There are advantages of strong specificity,durability,prevention of metastasis and recurrence,increased drug sensitivity and so on.Imiquimod(R837),a typical immune agonist,is currently studied for its bonded drugs,which has the advantages of controllable drug loading and stable structure,but also has some shortcomings and deficiencies,such as Low intratumoral drug delivery rate and not easy to control release due to stable structure.At the same time,due to the multi-drug resistance caused by the high heterogeneity and complexity of tumor cells,it is difficult for a single immunotherapy to achieve good results in the long-term clinical treatment process.Podophyllotoxin(PPT)is a chemotherapeutic agent that shows strong activity against P-glycoprotein mediated multidrug resistant cancer cells by simultaneously inhibiting P-glycoprotein overexpression and cancer cell growthing.Imiquimod agonists have the ability to activate the patient's own immune system specific long-term killing of cancer cells,and it can be used in combination with podophyllotoxin chemotherapeutic drugs to form an "immune reversal multi-drug resistance mechanism" to kill cancer cells on a large scale through the combined effect,at the same time containing the spread and metastasis of cancer cells.In this thesis,the physiological environment where there is a difference p H between tumor cell tissues and normal cell tissues is used to optimize the drug release of the polymer-bound drug at the tumor site.That is,the biodegradable amphiphilic block polymer mPEG-b-PLA and 2-aminoethanethiol obtain a block polymer containing pendant amino groups through the mercapto-ene click reaction.Followed by the introduction of 4-(hydroxymethyl)benzaldehyde-4-nitrophenyl carbonochloridate small molecule intermediate,Imiquimod drug is functionalized with aldehyde groups to obtain R837-CHO.Finally,the modified drug is bonded to the main chain of the amphiphilic block polymer containing pendant amino groups by mild Schiff base reaction to obtain intelligent polymer bonding drug mPEG-b-P(LA-g-R837)of immunomodulatory effect.In addition,an intelligent polymer bonding drug based on the combined action of immunomodulators and chemotherapeutics was also prepared in this thesis,to triggerthe immune system exerting its immune effect and avoid the resistance caused by long-term use of R837.That is,the biodegradable amphiphilic block polymer mPEG-b-PCl was first synthesized,and then the podophyllotoxin and R837-CHO were modified into podophyllotoxin with thiol groups at the ends PPT-R-HS and the imiquimod with thiol groups at the ends R837-C=N-R-HS small molecule.Finally,the mercapto-functionalized two drugs and the amphiphilic block polymer are reacted by the mercapto-bromine click reaction by one-pot method to obtain the polymer-bonded drug mPEG-b-P(Cl-g-R837/PPT).Both of the synthesized anti-tumor prodrugs can self-assemble in water to form nanomicelles,and DLS and fluorescence spectroscopy were used to test the size,potential characterization and critical micelle concentration of the micelles.The drug sustained-release ability of the bonded single drug and the bonded double drug is improved,which were also verified by in vitro drug release experiments.The results show that the prodrug micelles meet the conditions of endocytosis in vivo,and have excellent drug sustained-release performance under simulated tumor cell environment.In addition,the in vitro cell experiment of R837-bonded single drug showed that it has good biocompatibility and the ability of activating immune cells.