Photoresponsive glycopolymer aggregates as controlled release systems

Abstract

The use of a new block copolymer made up of poly(azobenzene methacrylate) (PMAzo) and poly(3-O-4-vinylbenzoyl- D -glucopyranose) (PBG) is described for the solubilization of waterinsoluble dyes such as Nile Red in aqueous solutions. This polymer, which is abbreviated as PMAzo -b- PBG, self-assembles into spherical aggregates in water as confi rmed by atomic force microscopy. UV irradiation of the aqueous polymer solution destabilizes the aggregates brought about as a result of the trans–cis isomerization of the MAzo units. Dissociated aggregates reunite to form tubular aggregates when the solution is irradiated with 450 nm light. Nile Red, which is a hydrophobic dye, can be incorporated into these aggregates and subsequently released using UV light. The encapsulation, release, and re-encapsulation of Nile Red are studied using fl uorescence spectroscopy.