A sulfonated mesoporous silica nanoparticle for enzyme protection against denaturants and controlled release under reducing conditions

Abstract Mesoporous silica nanoparticles (MSiNPs) are attractive enzyme hosts, but current MSiNPs are limited by leaching, poor enzyme stabilization/protection, and difficulty in controlling enzyme release. Sulfonated MSiNPs are promising alternatives, but are challenged by narrow channels, lack of control over enzyme adsorption to particle surfaces, and controlled release of enzyme. By introducing amines on particle surfaces and sulfonate groups into the channels via disulfide bonds, we developed a unique sulfonated MSiNP to selectively encapsulate enzymes to the channels with enhanced enzyme stabilization under denaturing conditions. Via pore-expansion, the channel diameter was increased which allows for encapsulating nm-sized enzymes. This new concept/strategy to immobilize and deliver enzymes or other biomacromolecules were demonstrated using two model enzymes. Furthermore, we combine site-directed spin labeling with Electron Paramagnetic Resonance to confirm the enhanced enzyme-host interaction and reveal the preferred enzyme orientation in the channels. Lastly, the presence of disulfides allows for enzyme release under reducing conditions, a great potential for cancer treatments. To the best of our knowledge, this is the first report of sulfonated MSiNPs that simultaneously offer enhanced stability against denaturants and controlled release of enzymes under reducing conditions, with enzyme orientation resolved in the channels.