Synergistic in-situ growth of silver nanoparticles with nanozyme activity for dual-mode biosensing and cancer theranostics

A multifunctional nanocomposite of AgNPs@GQDs is prepared by synergistic in-situ growth of silver nanoparticles (AgNPs) on the complex of tannic acid (TA) and graphene quantum dots (GQDs) for the construction of dual-mode biosensing platform and cancer theranostics. The nanocomposite exhibits a hydrogen peroxide (H₂O₂)-responsive degradation, in which Ag⁰ is oxidized to Ag⁺ along with the release of oxidized TA and GQDs. The degradation induces the decreased absorbance and enhanced fluorescence (FL) intensity due to the suppression of Förster resonance energy transfer (FRET) in AgNPs@GQDs, which is employed for colorimetric/fluorescence dual-mode sensing of H₂O₂. The intrinsic peroxidase-like activity of GQDs nanozyme can effectively catalyze the oxidation reaction, enhancing the detection sensitivity significantly. Based on the generation of H₂O₂ from the oxidation of glucose with the catalysis of glucose oxidase (GOx), this nanoprobe is versatilely used for the determination of glucose in human serum. Further, through combining the H₂O₂-responsive degradation of AgNPs@GQDs with high H₂O₂ level in cancer cells, the nanocomposites exhibit good performance in cancer cell recognition and therapy, in which the synergistic anticancer effect of Ag⁺ and oxidized TA contribute to effective cell death, and the liberated GQDs are used to monitor the therapeutic effect by cell imaging.