Immobilization of Carbon Dots in Molecularly Imprinted Microgels for Optical Sensing of Glucose at Physiological pH

Nanosized carbon dots (CDs) are emerging as superior fluorophores for biosensing and a bioimaging agent with excellent photostability, chemical inertness, and marginal cytotoxicity. This paper reports a facile one-pot strategy to immobilize the biocompatible and fluorescent CDs (∼6 nm) into the glucose-imprinted poly­(<i>N</i>-isopropylacrylamide-acrylamide-vinylphenylboronic acid) [poly­(NIPAM-AAm-VPBA)] copolymer microgels for continuous optical glucose detection. The CDs designed with surface hydroxyl/carboxyl groups can form complexes with the AAm comonomers via hydrogen bonds and, thus, can be easily immobilized into the gel network during the polymerization reaction. The resultant glucose-imprinted hybrid microgels can reversibly swell and shrink in response to the variation of surrounding glucose concentration and correspondingly quench and recover the fluorescence signals of the embedded CDs, converting biochemical signals to optical signals. The highly imprinted hybrid microgels demonstrate much higher sensitivity and selectivity for glucose detection than the nonimprinted hybrid microgels over a clinically relevant range of 0–30 mM at physiological pH and benefited from the synergistic effects of the glucose molecular contour and the geometrical constraint of the binding sites dictated by the glucose imprinting process. The highly stable immobilization of CDs in the gel networks provides the hybrid microgels with excellent optical signal reproducibility after five repeated cycles of addition and dialysis removal of glucose in the bathing medium. In addition, the hybrid microgels show no effect on the cell viability in the tested concentration range of 25–100 μg/mL. The glucose-imprinted poly­(NIPAM-AAm-VPBA)-CDs hybrid microgels demonstrate a great promise for a new glucose sensor that can continuously monitor glucose level change

Biocompatible Chitosan–Carbon Dot Hybrid Nanogels for NIR-Imaging-Guided Synergistic Photothermal–Chemo Therapy

Multifunctional nanocarriers with good biocompatibility, good imaging function, and smart drug delivery ability are crucial for realizing highly efficient imaging-guided chemotherapy in vivo. This paper reports a type of chitosan–carbon dot (CD) hybrid nanogels (CCHNs, ∼65 nm) by integrating pH-sensitive chitosan and fluorescent CDs into a single nanostructure for simultaneous near-infrared (NIR) imaging and NIR/pH dual-responsive drug release to improve therapeutic efficacy. Such CCHNs were synthesized via a nonsolvent-induced colloidal nanoparticle formation of chitosan–CD complexes assisted by ethylenediaminetetraacetic acid (EDTA) molecules in the aqueous phase. The selective cross-linking of chitosan chains in the nanoparticles can immobilize small CDs complexed in the chitosan networks. The resultant CCHNs display high colloidal stability, high loading capacity for doxorubicin (DOX), bright and stable fluorescence from UV to NIR wavelength range, efficient NIR photothermal conversion, and intelligent drug release in response to both NIR light and change in pH. The results from in vitro tests on cell model and in vivo tests on different tissues of animal model indicate that the CCHNs are nontoxic. The DOX-loaded CCHNs can permeate into the implanted tumor on mice and release drug molecules efficiently on site to inhibit tumor growth. The additional photothermal treatments from NIR irradiation can further inhibit the tumor growth, benefited from the effective NIR photothermal conversion of CCHNs. The demonstrated CCHNs manifest a great promise toward multifunctional intelligent nanoplatform for highly efficient imaging-guided cancer therapy with low side effects

Near-Infrared- and Visible-Light-Enhanced Metal-Free Catalytic Degradation of Organic Pollutants over Carbon-Dot-Based Carbocatalysts Synthesized from Biomass

Cost-efficient nanoparticle carbocatalysts composed of fluorescent carbon dots (CDs) embedded in carbon matrix were synthesized via one-step acid-assisted hydrothermal treatment (200 °C) of glucose. These as-synthesized CD-based carbocatalysts have excellent photoluminescence (PL) properties over a broad range of wavelengths and the external visible or NIR irradiation on the carbocatalysts could produce electrons to form electron–hole (e^––h⁺) pairs on the surface of carbocatalysts. These restant electron–hole pairs will react with the adsorbed oxidants/reducers on the surface of the CD-based carbocatalysts to produce active radicals for reduction of 4-nitrophenol and degradation of dye molecules. Moreover, the local temperature increase over CD-based carbocatalyst under NIR irradiation can enhance the electron transfer rate between the organic molecules and CD-based carbocatalysts, thus obviously increase the catalytic activity of the CD-based carbocatalyst for the reduction of 4-nitrophenol and the degradation of dye molecules. Such a type of CD-based carbocatalysts with excellent properties and highly efficient metal-free photocatalytic activities is an ideal candidate as photocatalysts for the reduction of organic pollutants under visible light and NIR radiation

Porous Carbon Protected Magnetite and Silver Hybrid Nanoparticles: Morphological Control, Recyclable Catalysts, and Multicolor Cell Imaging

A simple and facile synthetic strategy is developed to prepare a new class of multifunctional hybrid nanoparticles (NPs) that can integrate a magnetic core with silver nanocrystals embedded in porous carbon shell. The method involves a one-step solvothermal synthesis of Fe₃O₄@C template NPs with Fe₃O₄nanocrystals in the core protected by a porous carbon shell, followed by loading and in situ reduction of silver ions in the carbon shell in water at room temperature. The core–satellite and dumbbell-like nanostructures of the resulted Fe₃O₄@C–Ag hybrid NPs can be readily controlled by loading amount of silver ions. The hybrid NPs can efficiently catalyze the reduction reaction of organic dyes in water. The easy magnetic separation and high stability of the catalytically active silver nanocrystals embedded in the carbon shell enable the hybrid NPs to be recycled for reuse as catalysts. The hybrid NPs can also overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells in multicolor modal, with no cytotoxicity. Such porous carbon protected Fe₃O₄@C–Ag hybrid NPs with controllable nanostructures and a combination of magnetic and noble metallic components have great potential for a broad range of applications in the catalytic industry and biomedical field