The Biomedical Application Of Magnetic Mesoporous Silica Nanoparticles Loaded Short-stranded Nucleic Acids Or Proteins

Mesoporous silica nanoparticles (MSNs) are emerging as one of themost appealing candidates for drug carriers owing to their large surface area,ordered pore structure, super high specific pore volume, tunable pore size,and easy modification of surface. Among these, the loading and delivery ofbiological molecules is one of the most attractive research directions butdeveloped relatively slower than other anti-inflammatory and chemotherapydrugs delivery.In this study, we investigated the loading capacities of three typicalbiomolecules, i.e., the siRNA (~20bp), CpG oligonucleotides (~20nt), andurokinases (UK,~50kD) on magnetic MSNs (M-MSNs) with mesopore sizesof2.7nm,4.3nm, and6.1nm respectively. We also developed theirbiomedical applications for cancer gene therapy, immunotherapy andtargeted thrombolysis. While, the traditional nucleic acids loading strategyusing lipofectamine agent suffers from the big cytotoxicity, broad particledistribution, and intravenous vascular therapy also leads to the risk ofbleeding complications. Compared to these, our M-MSNs based drug vectorscan be more potentially utilized for in vivo therapy.In chapter2, we presented the material characterizations of these threepore sizes’ M-MSNs which get involved in this thesis. First, we synthesizedthe nanoparticles and characterized their morphologies, pore sizedistributions and magnetization curves. We further determined themorphologies and pore size distributions of M-MSNs (pore size of2.7nm)complexes which contained loaded siRNA and surface covered PEI layer.Additionally, the morphologies, diameter distributions and Zeta potentials of amino-modified or PEG-modified M-MSNs (4.3nm) were also exhibited.In chapter3, siRNA was encapsulated within the mesoporous structureof M-MSNs (2.7nm) under strongly dehydrated solution condition. Throughcoating polyethylenimine (PEI) on the surface of M-MSNs with siRNAexisting in the mesopores, we obtained a type of siRNA delivery vehicles(M-MSN_siRNA@PEI) with excellent siRNA protective capability andnegligible cytotoxicity. While, it was found that the RNAi efficiencymediated by M-MSN_siRNA@PEI was strongly dependent on theendosomal escape kinetics of the vehicles. We further found the entrapmentof siRNA within the endolysosomes and thus reducing the amount of siRNAto initiate RNAi were the essential reason for the lower efficiency of RNAi.Subsequently, the surface of M-MSN_siRNA@PEI was functionalizedthrough conjugating KALA peptides. The conjugation of KALA peptidefacilitated the endosomal escape of vehicles and thus resulted in an enhancedgene silencing effect in cells.In chapter4, amino-modified (abbreviated as M-MSN-A) or furtherPEG-modified (abbreviated as M-MSN-P) M-MSNs (4.3nm) weresynthesized for CpG adsorption and well particle dispersion. After that, westudied the CpG adsorption and desorption behaviors and the impact to thedrug cytosis of RAW264.7, which was explained from the degradation ofsilica and the delivery of the nanoparticles. The effects of inhibiting cancercells were also discovered by co-administration with the chemotherapy drug.Lastly, we investigated the immunostimulatory capability of such deliverysystems in vivo, which is considered to lay foundation for the cancer therapyin mouse models.In chapter5, a theoretical model providing the relationship betweenthrombolytic radius and UK diffusion time was established based on theFick’s second law and verified by experimental results using UK withdifferent activities. Subsequently, the UK (higher activity) adsorption anddesorption behaviors of M-MSNs were analyzed and found to be in well agreement with the relative equations in literatures. For the purpose ofrevealing the advantages of M-MSNs with enlarged pore size in targetthrombolysis, the efficacy of thrombolysis was investigated by a dynamicflow system in vitro. It suggested this kind of nanoparticle complex enhancedthe thrombolysis efficacy by3.5fold over the same amount of free UK anddisplayed outstanding controlled release efficacy. We also found that theloading efficiency of mesoporous silica nanoparticles basically depended onenzyme size and pore size matching.