Near-infrared light-triggered micelles for fast controlled drug release in deep tissue

In this manuscript, a near-infrared (NIR) light-breakable amphiphilic block copolymer N-succinyl-N′-4-(2-nitrobenzyloxy)-succinyl-chitosan micelles (SNSC), containing light-sensitive triggering group 2-nitrobenzyl alcohol on the hydrophobic block, was developed. The UV–Vis absorption spectra, Fourier Transform Infrared (FTIR) spectra, and 1H nuclear magnetic resonance (1H NMR) spectra were characterized to confirm the successful synthesis of the micelles. Two-photon photolysis of SNSC micelles was displayed by transmission electron microscopy (TEM). By encapsulating a NIR dye cypate (Ex/Em: 780/808 nm) into the hydrophobic core of the micelles, the dissociation of the micelles under NIR illumination was greatly accelerated, enabling a controlled fast release of co-loaded hydrophobic species in the micelles. In vivo distribution and acute toxicity of the NIR light-sensitive micelles were also investigated to verify the low cytotoxicity of the micelles. Results indicate that this system provides an efficient method to surmount the drawback of UV or visible light-responsive polymeric systems for controlled drug release in deep tissues.