Stabilizing silica nanoparticles in hydrogels: impact on storage and polydispersity

For a successful nanomedicine, it is important that the unique, size-dependent physicochemical proprieties of the nanomaterial remain predictably constant during both the storage and the manipulation with the material. Here a novel approach to preserve the colloidal stability and degradation of NPs is described. The concept is simple: a) solution of monodisperse particles is formulated into a responsive water- or PBS-based hydrogel; b) the gel can be reversibly turned into a solution after long term storage by shaking it by hand; c) the NP can be diluted and used in any desired application without the need for excessive manipulation. The differences between the physico-chemical properties of NPs stored in solution and in gel are compared. Two types of NPs were involved in this study: Silica NPs of ~100 nm and Au-NPs of 30 and 80nm in diameter. The key findings are: the fibrous matrix of the hydrogel limits the NP mobility, significantly reduces NP aggregation and conserves the NP morphology; both the hydrogelator and the NPs show negligible toxicity towards model, U937 human hematopoietic cell line; undesired leaching of cargo material loaded inside the particles is reduced, which could be an important feature for drug delivery systems.