Free Radical Polymerization of Gold Nanoclusters and Hydrogels for Cell Capture and Light-Controlled Release.

Gold nanocluster (AuNC) decorated hydrogels have attracted considerable attention as versatile biomaterials. To date AuNCs and hydrogels have mainly been mixed as independent components. Here, we report the use of AuNCs as reactive monomers in the polymerization of hydrogels. We used a free radical polymerization to copolymerize AuNCs with acrylamide and N-acryloyl glycinamide to prepare stimuli-responsive smart hydrogels. Multiple C═C bonds were decorated on the surface of the AuNCs as active sites for polymerization. These C═C bonds not only protected the structure of the AuNCs from oxidation by free radicals during polymerization but also covalently connected the AuNCs with the polymer chains. This structure ensured good photothermal performance of the AuNCs while preserving the thermoresponsive hydrogen bonds of polymers. Moreover, the copolymerized AuNCs acted as cross-linkers, which improved the mechanical properties of the hydrogels. These smart hydrogels had good stability, efficient photothermal conversion, and a sensitive thermoresponsive. We examined their potential for capture of MDA-MB-231 cells with hyaluronic acid as target molecules. The captured cells were released under 660 nm irradiation. This process of targeted capture and light-controlled remote release could be repeatedly applied. These results suggest that systems based on AuNCs copolymerized with hydrogels have great potential for biomedical applications.