Design and Synthesis of Redox Responsive and Enzyme Responsive Nanocarriers based on Mesoporous Silica Nanoparticles for Targeted Drug Delivery Applications
Srivardhan Reddy Gayam
|關鍵字:||二氧化矽奈米粒子;標靶藥物傳輸;奈米載體;mesoporous;silica;nanoparticles;drug delivery;cancer;stimuli responsive|
|摘要:||In this thesis, we have demonstrated that the design and synthesis of functional mesoporous silica nanoparticles for intracellular drug delivery. This research has taken us through a very exciting journey; starting from the synthesis of MSNPs with controlled shape and size, followed by the develop of site-specific nanovalve systems for MSNPs, continuing with the investigation of their in vivo and in vitro stimuli responsive payload release profiles and biocompatibilities. Finally describing their applications as intracellular drug delivery nanocarriers. In the first research work we have demonstrated the redox responsive, Pd (II) templated rotaxane nanovalve capped mesoporous silica nanoparticle for on command cancer targeted drug delivery applications. In which, the Pd(II) templated, mechanically interlocked rotaxane nanovalves with a folic acid terminal group, anchored by a disulfide bridge as a snap-top on the surface and the folic acid head group bestows targeting capability, specifically to cancer cells. MSNP-SS-FA nanoparticles loaded with the anticancer drug doxorubicin (Dox) were evaluated as a drug-release system in HeLa cell cultures and their effect on the apoptosis mechanism of the cells was studied with the MTT cell viability assay and biodistribution was visualized with the confocal laser scanning microscopy. No premature release in the absence of trigger molecules was observed, high viability of cells in the presence of these nanoparticles and elevated levels of apoptosis in drug loaded nanoparticle treated HeLa cells, compared to an equivalent amount of free drug clearly suggests that this design is a suitable alternative to transport and delivery of drugs in an extremely safe and effective manner.
In the second work, we have demonstrated the NAD(P)H: quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles (MSNPs) for on-command delivery applications. In which, the nanovalve system is made of mechanically interlocked molecules in the form of rotaxane formed by the inclusion of an α-cyclodextrin onto a diethyleneglycol stalk anchored on an MSNP surface, with a benzoquinone stopper integrated at end of the stalk. This design shows no premature release in an aqueous environment, where in the presence of NQO1, a significant payload release was observed due to the enzyme-triggered removal of nanovalve from the mesopores. This proves that the delivery mechanism of our nanoparticles was effective. Moreover, confocal cell images of A549, MCF-7 and HL-60 cells treated with this design of nanoparticles demonstrated the effective internalization of nanoparticles by both cells and was localized in the cytoplasm. Cell viability studies demonstrated that MSNP-NQO1 nanoparticles are nontoxic for A549 and HL-60 cells at the tested concentrations, proving that these nanoparticles are biocompatible. Cell viability reduced significantly in A549 cells (NQO1 +Ve) treated with Dox loaded MSNP-NQO1, whereas no significant change was observed in HL-60 cells. These observations show that the fabricated nanovalves on MSNP-NQO1 were selectively opened in the presence of NQO1 enzyme. More importantly, the Dox loaded MSNP-NQO1system demonstrated a good therapeutic effect on the inhibition of tumor growth in mice. Finally, the design of NQO1 responsive MSNP-NQO1 has proven to be an effective delivery system for the transportation of chemotherapeutic agents for theranostic applications. The results of these two works opens up a wide range of possibilities to transport and deliver drugs in an extremely safe and effective manner.
The multifunctional MSNPs has to be developed to provide a universal platform for theranostics and personalized medicine. Where multicomponent payloads are transported to target cells through the active recruitment of targeting ligands combined with biologically triggered responses that activate molecular nanovalves. As a future prospect of this work, we would like to develop the multifunctional nanovalves to selectively targets the diseased cells and activates to the endogenous responses|
In this Thesis, design and synthesis of redox responsive and enzyme responsive drug delivering nanocarriers, based on mesoporous silica nanoparticles for controlled targeted drug delivery applications are presented. The two topics have been investigated (1) redox responsive Pd (II) templated rotaxane nanovalve capped mesoporous silica nanoparticles and (2) NAD(P)H: quinone oxidoreductase 1 (NQO1) enzyme responsive α-cyclodextrin rotaxane nanovalve capped mesoporous silica nanoparticles for cancer targeted drug delivery applications. In the first work, gatekeeping of the mesopore is achieved by Pd(II) templated, mechanically interlocked rotaxane nanovalves with a folic acid terminal group, anchored by a disulfide bridge as a snap-top on the surface. The folic acid head group bestows targeting capability, specifically to cancer cells. Once nanoparticles enter the cancer cell, controlled release of the cargo is triggered by cleavage of the disulfide bond using an endogenous glutathione stimulus. In the second work, gatekeeping of MSNPs is achieved by the integration of mechanically interlocked rotaxane nanovalves on the surface of MSNPs. The rotaxane nanovalves system is composed of a linear stalk anchoring on the surface of MSNPs, an α-cyclodextrin ring that encircles it and locks the payload “cargo” molecules in the mesopores, and a benzoquinone stopper incorporated at the end of the stalk. The gate opening and controlled release of the cargo is triggered by cleavage of benzoquinone stopper using an endogenous NQO1 enzyme.