Towards biocompatible nanovalves based on mesoporous silica nanoparticles

Over the past two decades, cancer has ascended to become the number one or two cause of death in many nations worldwide. Encapsulation of anticancer drugs within nanocarriers that selectively target diseased cells promises to increase the effectiveness of conventional chemotherapy and decrease its side effects. Nanoparticles show great potential as superior intelligent drug delivery platforms. Among them, mesoporous silica nanoparticles (MSNs) are particularly interesting candidates for powerful drug carriers because of their unique characteristics and abilities to efficiently and specifically entrap cargo molecules. The biggest challenge in current development is the design and synthesis of controlled biocompatible nanovalves or cap systems on MSNs to realize zero premature release of drugs and targeted delivery of anticancer drugs in a controlled fashion for smart cancer therapies. This review article evaluates drug delivery systems which comprise MSNs functionalized with well-defined self-assembled layers of biocompatible molecular and supramolecular nanovalves based on (supra) molecular switches, polymers, and biomolecules. Recent research progress on MSN-based smart materials that can simultaneously address targeted delivery of anticancer drugs, ideally zero premature release, and controlled release by external physical, chemical and biological stimuli will be highlighted and discussed.