Mesoporous Silica Nanoparticle-Based Double Drug Delivery System for Glucose-Responsive Controlled Release of Insulin and Cyclic AMP

A boronic acid-functionalized mesoporous silica nanoparticle-based drug delivery system (BA-MSN) for glucose-responsive controlled release of both insulin and cyclic adenosine monophosphate (CAMP) was synthesized. Fluorescein isothiocyanate-labeled, gluconic acid-modified insulin (FITC-G-Ins) proteins were immobilized on the exterior surface of BA-MSN and also served as caps to encapsulate CAMP molecules inside the mesopores of BA-MSN. The release of both G-Ins and CAMP was triggered by the introduction of saccharides. The selectivity of FITC-G-Ins release toward a series of carbohydrate triggers was determined to be fructose > glucose > other saccharides. The unique feature of this double-release system is that the decrease of FITC-G-Ins release with cycles can be balanced by the release of CAMP from mesopores of MSN, which is regulated by the gatekeeper effect of FITC-G-Ins. In vitro controlled release of cAMP was studied at two pH conditions (pH 7.4 and 8.5). Furthermore, the cytotoxicity of cAMP-loaded G-Ins-MSN with four different cell tines was investigated by cell viability and proliferation studies. The cellular uptake properties of cAMP-loaded FITC-BA-MSN with and without G-Ins capping were investigated by flow cytometry and fluorescence confocal microscopy. We envision that this glucose-responsive MSN-based double-release system could lead to a new generation of self-regulated insulin-releasing devices.