Research On Anti-tumor Activity And Biomolecular Action Mechanism Based On Mesoporous Silica Drug-carrying System

Tumor-targeted transport of drugs and controlled release within tumor cells are the basis for ensuring efficient tumor therapy.Targeted transport prevents drug transport to non-lesional tissue cells and controls drug transport to designated tissue cells;controlled release can modulate the time of drug release and control drug concentration.The combination of targeted transport and controlled release allows the drug to be released after reaching the diseased cells under targeted action,reducing the side effects of the drug.Mesoporous silica(MSN)has a wide range of applications in the biomedical field due to its unique properties,such as easy structure regulation,easy surface modification and functionalization,large specific surface area,adjustable pore size and good biosafety.In this thesis,the photothermal trigger-controlled drug release system,anti-tumor activity and anti-tumor mechanism of mesoporous silica nanoparticles based on base pairing rules were studied.The main contents are as follows:(1)A photothermal trigger-controlled drug delivery system based on base pairing rules for mesoporous silica nanoparticles was designed and prepared.The principle of base pairing is based on the complementary pairing of adenine(A)with thymine(T)and guanine(G)and cytosine(C),which is the basis for the formation of the double helix structure of nucleic acid molecules.The above complementary pairing is stable at low temperature and normal temperature.As the temperature increases,the stability drops rapidly and the complementary pairing is separated.Based on this,mesoporous silica was prepared this paper and NH2 was modified on the surface.Then,MSN-T was formed by EDC/NHS coupling method.MSN-T was loaded with doxorubicin(DOX,chemotherapeutic drug)and indocyanine green(ICG,photothermal therapeutic drug),then mixed with poly A(a string of polyadenylation consisting of 200-250 adenine bases,which is the tail of the synthetic RNA strand during post-transcriptional RNA processing).Due to AT Pairing,the MSN's tunnel was closed quickly.Both in vitro and in vivo experiments have shown that DOX&ICG@MSN-T@poly A can remain stable at physiological temperatures,but can be heated by activating the ICG photothermal effect by 808 nm laser after entering the tumor cells.Then,poly A was detached and DOX was released to exert anticancer activity.In addition,ICG's photothermal conversion performance not only provides temperature-raising function for drug release,but also treats tumors by photothermal therapy(PTT)in combination with DOX,which inhibits tumor growth and activates anti-tumor immunity effectively.This has enormous potential for chemotherapy combined with tumor chemotherapy.(2)DOX&ICG@MSN-T@poly A in vitro anti-tumor experiments have shown that MSN does not have anti-tumor activity and is highly biosafe.However,does MSN affect protein and nucleic acid structure after entering cells?In order to solve this problem,the interaction mechanism between MSN and human serum albumin was studied by UV-visible absorption spectroscopy,steady-state fluorescence spectroscopy,synchronous fluorescence spectroscopy,time-resolved fluorescence spectroscopy and circular dichroism spectroscopy.Then,the binding constant,the binding site and the type of interaction force are calculated by the theoretical formula.The results indicate that there is an interaction between human serum albumin and MSN,but the effect on the conformation of human serum albumin is not significant.That is,the biological activity of human serum albumin is not fundamentally changed.(3)The UV-vis spectroscopy,fluorescence spectroscopy,FTIR,DSC and circular dichroism spectroscopy were used to study the binding constant,the interaction site and the conformational changes of calf thymus DNA,which revealed that there was an interaction between MSN and the double helix structure of calf thymus DNA molecule,but there was no obvious displacement phenomenon.MSN also had a influence on DNA base stacking,which proved that it's not just a simple physical mix,it's also combined by a certain amount of force between the calf thymus DNA and MSN.However,this effect does not substantially change the biological activity of DNA.The above findings provide valuable reference for objective evaluation of the effects in cancer therapy and potential toxic side effects of MSN,and also further verified the safety of the prepared mesoporous silica from the molecular perspective.