Mesoporous silica nanoparticles (MSN) have potential as drug delivery and controlled release devices due to their high surface area and absorption capabilities. The effect of surface charge and pH on the release of the fluorescent dye, rhodamine 6G, from MSN has been studied. Release profiles of rhodamine 6G from bare and amine-coated MSN at pH 5.0 and 7.4 are very different and demonstrate that electrostatic interactions between entrapped rhodamine 6G molecules and the charged surface of the MSN have a significant effect on release kinetics. Release of rhodamine 6G from amine-coated MSN can be fit to a single exponential function, while release from bare MSN can be fit to a double exponential function—indicating that the release of rhodamine 6G from bare MSN is a two-phase process. In addition, it was determined that MSN need to be sonicated in dye solution to maximize their loading capacity.Graphical abstractResearch highlights► Sonication of MSN in dye solution is necessary to maximize the loading capacity of the MSN. ► Electrostatic interactions between entrapped R6G molecules and the charged surface of the MSN are responsible for differences in release profiles of bare and APTES-functionalized MSN. ► Release profiles from APTES-coated MSN better fit a single exponential function while release profiles from bare MSN better fit a double exponential function—indicating that the release of R6G from bare MSN is a two-phase process.

We demonstrate that multiphoton-absorption-induced luminescence (MAIL) is an effective means of monitoring the uptake of targeted nanoparticles into cells. Gold nanoparticles (AuNPs) with diameters of 4.5 and 16 nm were surface-functionalized with monocyclic RGDfK, an RGD peptide analogue that specifically targets the αvβ3 integrin, a membrane protein that is highly overexpressed in activated endothelial cells during tumor angiogenesis. To determine whether cyclic RGD can enhance the uptake of the functionalized AuNPs into activated endothelium, human umbilical vein endothelial cells (HUVECs) were used as a model system. MAIL imaging of HUVECs incubated with AuNPs demonstrates differential uptake of AuNPs functionalized with RGD analogues: RGDfK-modified nanoparticles are taken up by the HUVECs preferentially compared to AuNPs modified with linear RGD (GRGDSP) conjugates or with no surface conjugates. The luminescence counts observed for the AuNP-RGDfK conjugates are an order of magnitude greater than for AuNP-GRGDSP conjugates. Transmission electron microscopy shows that, once internalized, the AuNP-RGDfK conjugates remain primarily within endosomal and lysosomal vesicles in the cytoplasm of the cells. Significant aggregation of these particles was observed within the cells. MAIL imaging studies in the presence of specific uptake inhibitors indicate that AuNP-RGDfK conjugate uptake involves a specific binding event, with αvβ3 integrin-mediated endocytosis being an important uptake mechanism.

In this paper we describe the modification of anionic surfactant vesicles with surfactant-based glycoconjugates of glucose, lactose, maltose and maltotriose. Catanionic vesicles were prepared by mixing cetyltrimethylammonium tosylate and sodium dodecylbenzenesulfonate to obtain thermodynamically stable, spontaneously formed vesicles. Carbohydrate moieties were linked to a hydrocarbon chain via an N-glycosyl linkage to produce an amphiphilic glycoconjugate that undergoes hydrophobic insertion into the outer bilayer leaflet of the surfactant vesicle. Once inserted, the bioavailability of the surface-adsorbed carbohydrates was determined using agglutination of the modified vesicles through selective binding of the lectins concanavalin A and peanut agglutinin. In these studies, glycoconjugates were present in the vesicle bilayer at a carbohydrate-to-surfactant ratio of approximately 1 : 100. At this coverage, vesicle formation is uninhibited, the carbohydrate groups are displayed on the vesicle outer surface and bind selectively to lectins in solution. The preparation of stable, carbohydrate-functionalized, anionic surfactant vesicles may prove useful in the targeted delivery of molecular payloads such as dyes or drugs to cells with high selectivity for a wide range of biotechnological applications.