A NO photoreleasing supramolecular hydrogel with bactericidal action

We have developed an engineered hydrogel formed, in the absence of any toxic solvents or reagents, by spontaneous self-assembly of three key components: a poly-beta-cyclodextrin polymer (1), a hydrophobically modified dextran (2) and a nitric oxide (NO) photodonor bearing an adamantyl appendage (3). The formation of this supramolecular assembly is based on a "lock-and-key" mechanism in which the alkyl side chains of 2 and the adamantane moiety of 3 form inclusion complexes with the beta-CD cavities of 1. The multivalent character of the interactions between all components and the insolubility of the NO photodonor in an aqueous medium ensure the stability of the hydrogel and the total lack of leaching of the photoactive component from the gel network under physiological conditions, even in the absence of protective coating agents. The photochemical properties of the NO photodonor are well preserved in the supramolecular matrix as demonstrated by the remote-controlled release of NO through visible light excitation and its transfer to a protein such as myoglobin. The utility of this NO photoreleasing platform is demonstrated in effective and strictly light-dependent bactericidal activity against the Gram-negative Escherichia coli bacterial colony suspension.