Diazonaphthoquinone-based amphiphilic polymer assemblies for NIR/UV light- and pH-responsive controlled release

Here, a novel near-infrared (NIR)/ultraviolet (UV) light-, pH-and temperature-responsive amphiphilic polymer, poly(ethylene glycol)-block-poly(dimethylaminoethyl methacrylate)@2-diazo-1,2-naphthoquinone (PEG-PDMAEMA@DNQ), is synthesized via an atom transfer radical polymerization (ATRP) and quaternization reaction. In aqueous solution, this amphiphilic polymer could self-assemble into spherical assemblies with hydrophobic NIR/UV light and base responsive DNQ moieties as the core and hydrophilic PEG and pH/temperature-responsive PDMAEMA as the corona. The NIR/UV light-and pH-sensitive absorbances of the polymer were characterized by UV-vis spectroscopy. Under 365 nm UV or 808 nm NIR irradiation, the characteristic absorption intensity of DNQ gradually decreased, indicating that DNQ converted to 3-indenecarboxylic acid (3-IC) via the Wolff rearrangement. Under acidic conditions, the absorption spectra changed little, while the absorption peak at around 400 nm decreased and a new absorption peak at 350 nm appeared under basic conditions. The morphological changes of the assemblies, which could be dissociated after UV/NIR irradiation, swollen under acidic conditions, while turned into nanocapsules under basic conditions and shrunk above the lower critical solution temperature (LCST), were revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The loaded hydrophobic model molecules coumarin 102 could be released from the assemblies in response to NIR, UV light and pH. More importantly, the release efficiency could be enhanced dramatically under combined stimulation. The reported NIR/UV light-and pH-responsive polymer assemblies would have great potential as nanocarriers for controlled release.