Enzyme/Laser-responsive Controlled Drug Release Systems Based On Mesoporous Silica Nanoparticles And Their Biological Evaluations

Along with interdisciplinary fusion of bioscience, materials science, pharmacy and clinical medicine etc., nanobiomedicine has witnessed considerable achievements. Some functional nano-materials have displayed tremendous potential for applications in diagnosis, diseases alert and drug delivery etc. Particularly in the field tumor therapy, by surface modifying nanoparticles with functional molecules, which endowed the nanoparticles with tumor targeting intelligent responsive controlled drug release, so as to efficiently deliver drug to tumor site. The functionalized nanoparticles could not only improve the efficiency of tumor therapy, but also simutaniously reduce the toxic side effect on healthy cells/organs.Mesoporous silica nanoparticles(MSNs) attract much attention due to their unique features, such as large surface area and pore volume, tunablepore size, ordered structure and a large amount of active hydroxyl groups(-OH) on the surfaces. MSNs have been widely investigated in the fields of bioimaging, diagnosis, biosensor, biocatalysis and drug delivery. As for tumor therapy drug delivery sysytem, it is urgent to solve the problems as follows:(1) how to construct an intelligent stimuli-responsive gatekeeper onto the surfaces of MSNs that could control on-demand drug delivery at malignant tumor tissue; and(2) how to evaluate the therapeutic effects of MSNs-based drug delivery system with an animal tumor model and biosafty, and thus to provide scientific evidence for its potential clinc application.To solve above-mentioned problems, this study employed MSNs and hollow mesoporous silica nanoparticles(HMSNs) to construct two types of controlled drug release systems: matrix metalloproteinases(MMPs) responsive MSNs controlled drug release system and near-infrared laser(NIR) responsive HMSNs controlled drug release system. A series of materials characterizations, controlled drug release and biological evaluations in vitro and in vivo were performed on these systems. The study provides scientific evidence for the potential clinic application of MSNs and HMSNs. The main contents of this study are listed as follows:① Synthesis and characterization of MSNs and HMSNsMCM-41 type MSNs were synthesized through hydrolyzation of tetraethoxysilane and CTAB as template. Si O2@CTAB-Si O2 nanoparticles with core-shell structure were synthesized based on solid Si O2 and CTAB. The HMSNs were synthesized by Na2CO3 etching. Transmittance electron microscopy(TEM) and scanning electron microscopy(SEM) observations confirmed that MSNs displayed good dispersity, ordered pores and with dimensions of around 100 nm;HMSNs displayed obvious hollow structure, ordered pores, good dispersity and with diameters of about 160 nm. XRD analysis showed that both MSNs and HMSNs had derivative peaks at 2.2 degree(2θ), suggesting that the two types of nanoparticles had mesoporous structures. BET and BJH results showed that the surface areas and pore volumes of MSNs were 959.47 m2/g and 0.962 cm3/g, respectively; whereas the HMSNs were 1396.60 m2/g and 1.32 cm3/g, respectively.② Construction of MMPs responsive controlled drug release system based on MSNs and its biological evaluationsIn this charpter, we designed and constructed a MMPs-responsive controlled drug release system(MSNs-Peptide-BSA-LA) by using BSA as end-cap, peptide substrate of MMPs as intermediate linker, lactobionic acid as targeting moiety and MSNs as drug carrier. The results of TEM, FITR, Zeta potential measurements, fluorescamine detection, BET, BJH and TGA confirmed that amino groups, polypeptide, bovine serum albumin(BSA) and lactobionic acid(LA) were successfully conjugated to the MSNs surfaces of MSNs.The drug release behaviors suggested that the MSNs-Peptide-BSA-LA system could be triggered by MMPs. Cell viability assayand confocal laser scanning microscopy(CLSM) observations revealed that MSNs-Peptide-BSA-LA@DOX could effectively inhibit the proliferation of Hep G2 cancer cells. Flow cytometry, TEM and CLSM observations were used to characterize the interactions between Hep G2 cells and the controlled drug release system. The results suggested that MSNs-Peptide-BSA-LA system could target and be efficiently uptaken by Hep G2 cells.The endocytosed nanoparticles were distributed at cytoplasm, while not penetrating intocell nuclei. Finally, tumor model of nude mice in vivo suggested that MSNs-Peptide-BSA-LA@DOX system induced apoptosis of tumor cells, thus inhibiting the tumor growth. Mice weight and H&E staining assay of main organs of nude mice suggested that the fabricated systemhas only limited toxic side effect on the major organs of nude mice.③ Construction of NIR laser-responsive controlled drug release system based on HMSNs and its application in chemo-photothermal combination therapy for liver cancer.In this chapter, we designed and constructed a controlled drug release system based on HMSNs. The system was constructed by filling a phase-change materials(PCM) of 1-tetradecanol and drugs into HMSNs that could be triggered by NIR laser with thermo-chemo combination cancer therapy. DOX, indocyanine(ICG) and 1-tetradecanol were loaded into HMSNs. The system could achieve near ―zero release‖ in the process during drug delivery due to the solidification of 1-tetradecanol to DOX and ICG. The system was triggered by NIR laser to release drug and induced the photothermal effect of ICG, thus realizing chemo-photothermal combination therapy for liver cancer. The results of TEM, TGA and elemental analysis confirmed that the DOX, ICG and 1-tetradecanol were successfully loadedinto HMSNs.The drug release behaviors suggested that DOX could be released from HMSNs@DOX-ICG@PCM system triggering by NIR laser with thermal energy. It displayed great potential to achieve thermo-chemo combination cancer therapy. Cell cytotoxicity and CLSM observations revealed that HMSNs@DOX-ICG@PCM could effectively inhibit the proliferation of Hep G2 cells. TEM observation was used to characterize the cellular uptake. The result suggested that the endocytosed nanoparticles were located at endosome while not penetrating into the cell nuclei. Finally, tumor model of nude mice in vivo suggested that the combination therapy of HMSNs@DOX-ICG@PCM could efficiently inhibit the tumor growth, induce the apoptosis of cancer cells and prolong survival time of nude mice. Mice weight and H&E staining assay of main organs of nude mice suggested that free DOX led to weight decrease and cardiotoxicity of nude mice; wherease combination therapy of HMSNs@DOX-ICG@PCM had only limited toxic side effects on the major organs of nude mice.