Superparamagnetic Core–Mesoporous Silica Shell Nanoparticles with Tunable Extra- and Intracellular Dissolution Rates

Mesoporous silica nanoparticles have repeatedly been shown to be a promising drug carrier because of their high porosity, biocompatibility, and inherent degradability. The kinetics of degradation is an extremely important parameter, as both the clearance time in vivo and, in many cases, the drug delivery kinetics are closely linked to the dissolution rate. Thus, a synthetic means to control the dissolution rates is an important part of nanoparticle optimization for a given application. Another important parameter influencing the fate of the nanoparticles in a biological system is their size. Optimally, it should therefore be possible to independently tune the dissolution rate without simultaneously changing the particle size. Here, we present means to achieve this by looking at both intracellular and extracellular degradation, using mesoporous silica shell-SPION core nanoparticles, where the porosity of the shell can postsynthetically be varied without changing the original size of the particles in combination with the macrophage cell line J774.A1. Furthermore, it is also shown that the kinetics of intracellular silica dissolution is much slower than that of extracellular dissolution. However, the trends in terms of dissolution kinetics for the different particles also hold for intracellular dissolution. Furthermore, our results also indicate that the intracellular dissolution kinetics are related to the nanoparticle concentration within vesicular compartments.