Study On A Sustained-release And Targeting Drug Delivery System Based On Mesporous Silica Nnaoparticles And The Pharmacodynamics Study On Colorectal Cancer

[Background]Chemotherapy is one of the indispensable treatments for advanced cancer patients.However,traditional anticancer drugs are distributed throughout the body,unable to specifically recognize tumor cells,and it is difficult to achieve and maintain effective drug concentrations in vivo,which can easily cause serious toxic and side effects,limiting the clinical therapeutic effect of chemotherapy drugs.As a new therapeutic method,nanoparticles-based drug delivery system has become a emerging field of drug and medicine recent years.Therefore,the preparation of nanocarriers with appropriate particle size,good biocompatibility,large drug load and targeting effect has become an ideal choice for clinical cancer treatment.[Objective]In this study,a mixed nano-drug delivery platform based on mesporous silica nanoparticle（MSN）coated with the supported lipid bilayer（SLB）and ligand-modified was prepared.MSN is an excellent drug carrier with suitable particle size and unique structure,physical and chemical properties.SLB further improves the biocompatibility of MSN,reduces the premature release of drugs and the non-specific binding,and prolongs the drug circulation time.Enhancing drug aggregation in tumor sites through ligand-mediated specific cellular uptake.In addition,ligands modified on nanoparticles can exert its own therapeutic effect in antimigration.In this work,the antimetabolic drug fluorouracil was used as the model drug to load into MSN.SLB coated on the surface of MSN;Cetuximab（CTX）,an Ig G1 monoclonal antibody,was modified onto the surface of the nanoparticles as ligand to construct a novel drug delivery system that can actively target colorectal cancer（CRC）and provide a possible theoretical basis and guidance for subsequent tumor therapy.[Materials and methods]Firstly,MSN was synthesized using TEA as catalyst and CTAC as template.MSN-NH₂ was obtained by amino modification of MSN using APTES by delayed co-condensation method.MSN-FITC was synthesized by fluorescein isothiocyanate（FITC）modification of MSN-NH₂ for nanoparticle tracking.To further improve the biocompatibility of MSN and prolong its circulation time in vivo,the phospholipid bilayer was fabricated to obtain SLB-MSN for reducing non-specific cell binding in vivo.Considering the complexity of cancer therapy,to further improve the in vivo targeting of nanocarriers,CTX was selected as the ligand for functionalized modification of SLB-MSN in this study,and finally CTX-SLB-MSN was prepared.Then 5-fluorouracil（5-FU）,a conventional chemotherapy drug for colorectal cancer,was selected as the model drug for drug loading experiment,and the drug loading content and encapsulation efficiency of this drug delivery system were determined.Then the drug release behavior of MSN and SLB-MSN in vitro was investigated.The effect on cytotoxicity,cell cycle and apoptosis of MSN,SLB-MSN and CTX-SLB-MSN before and after drug loading were investigated in vitro.The in vivo and in vitro targeting properties of MSN-FITC,SLB-MSN-FITC and CTX-SLB-MSN-FITC were verified,and the inhibition of receptor competition of CTX-SLB-MSN-FITC nanoparticles was also investigated in vitro.[Results]The results show that the average particle size of the synthesized MSN is57nm and the dispersion is uniform.Compared with MSN,the particle size of SLB-MSN is increased,and the dispersion is uniform and stable.The physical and chemical properties,structures of the nanoparticles were not significantly changed after CTX modification.In vitro results of cellular uptake showed that the monoclonal antibody modified nanoparticles were internalized in tumor cells with high EGFR expression.In vitro functional experiments showed that the drug free drug nanoparticles inhibited the invasion and metastasis of tumor cells,and the molecular mechanism results showed that CTX-SLB-MSN inhibited the invasion and metastasis of tumor cells by blocking the activation of EGFR classical signaling pathway.After drug loading,the loading content and encapsulation efficiency were 15.07%and 37.67%,respectively.In vitro release experiments showed that SLB encapsulated nanocarriers had good stability and controlled effect on drug release.The cytotoxicity examination in vitro showed that the blank nanocarriers had good biocompatibility.The drug delivery system showed specific cytotoxicity,cycle arrest and induction of apoptosis.In vivo distribution experiments showed that the targeted nanocarriers had obvious aggregation and retention in tumor sites.[Conclusion]In summary,we integrated MSN,SLB,and CTX to construct a nanoplatform which could stably accommodate a water-soluble chemotherapeutic agent,deliver the payload to EGFR positive CRC cells in a targeted manner,and combine the anti-tumor capabilities of antibodies and chemotherapeutics.MSN mainly acted as a uniform nanocarrier,and it efficiently encapsulated the anticancer agent 5-FU.The SLB not only contributed to the biocompatibility and colloidal stability but also prevented the burst release of the loaded cargo.The introduction of CTX enabled the nanocarrier to specifically recognize the EGFR overexpressed on the surface of CRC cells.Moreover,the targeting abilities of CTX-SLB-MSN were further confirmed by biodistribution experiments in vivo.The loaded 5-FU was efficiently delivered to the targeted cells and ultimately killed them.In addition to strong tumor-homing capacity,the CTX docked on the nanoplatform significantly inhibited the migration and invasion of CRC cells through downregulating the EGFR mediated PI3K/AKT signaling pathway.Conclusively,this nanoplatform is a promising candidate for CRC treatment.