“…Some very suitable inorganic nanocarriers to be functionalized with appropriate hydrogel gatekeeper are mesoporous silica nanoparticles (MSNs) [ 19 , 25 ]. MSNs are characterized by a high specific surface area, an adjustable pore size, high hydrothermal stability, a large pore volume, biocompatibility and very low toxicity [ 19 , 26 , 27 , 28 , 29 ]. Moreover, their internal and external surface is highly covered with silanol groups, which can easily undergo functionalization [ 29 ].…”