Photoregulation of drug release in azo-dextran nanogels

A simple photoresponsive azo-dextran polymer has been investigated for its ability to act as a nanogel drug carrier. Self aggregation of the azo-dextran polymer leads to the formation of nanogels, AD (5 and 10) in aqueous media, which were characterized by TEM and DLS. When examined under UV light (365 nm), the unloaded nanogels, which were observed to be in the range of 120-290 nm, show dependence on the degree of crosslinking, pH and ionic concentration of the dispersed media. Nanogels, AD (5 and 10), have been loaded with a model fluorophore, rhodamine B and a drug, aspirin, by freeze drying an aqueous dispersion of the nanogels in the presence of the substrate dissolved in water or PBS buffer. The release pattern of the encapsulated bio-active molecules from these nanogels was regulated by (trans-cis) photoisomerization of the azobenzene moiety present in the crosslinker. A comparison of the release behavior of the loaded (rhodamine, aspirin) AD (5 and 10) nanogels reveal that the rate of release of the encapsulated active molecules from the nanogels was slower when the azo moiety was in E-configuration as compared to that the azo in the Z-configuration. The in vitro release behavior of drug from these polymeric micellar systems is revelative of the potential of the nanogels for targeted drug delivery in nanomedicine. (c) 2007 Elsevier B.V. All rights reserved.