Responsive polymer-fluorescent carbon nanoparticle hybrid nanogels for optical temperature sensing, near-infrared light-responsive drug release, and tumor cell imaging

Fluorescent carbon nanoparticles (FCNPs) have been successfully immobilized into poly(N-isopropylacrylamide-co-acrylamide) [poly(NIPAM-AAm)] nanogels based on one-pot precipitation copolymerization of NIPAM monomers with hydrogen bonded FCNP-AAm complex monomers in water. The resultant poly(NIPAM-AAm)-FCNP hybrid nanogels can combine functions from each building block for fluorescent temperature sensing, cell imaging, and near-infrared (NIR) light responsive drug delivery. The FCNPs in the hybrid nanogels not only emit bright and stable photoluminescence (PL) and exhibit up-conversion PL properties, but also increase the loading capacity of the nanogels for curcumin drug molecules. The reversible thermo-responsive swelling/shrinking transition of the poly(NIPAM-AAm) nanogel can not only modify the physicochemical environment of the FCNPs to manipulate the PL intensity for sensing the environmental temperature change, but also regulate the releasing rate of the loaded anticancer drug. In addition, the FCNPs embedded in the nanogels can convert the NIR light to heat, thus an exogenous NIR irradiation can further accelerate the drug release and enhance the therapeutic efficacy. The hybrid nanogels can overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells upon laser excitation. The demonstrated hybrid nanogels with nontoxic and optically active FCNPs immobilized in responsive polymer nanogels are promising for the development of a new generation of multifunctional materials for biomedical applications.