Au/N-Doped Carbon Dot Nanozymes as Light-Controlled Anti- and Pro-Oxidants

Abstract

Disturbances in the redox state of a biological system can cause diverse effects and clinical functions. The key and difficulty lies in controlling the balance between reduction and oxidation. Nanomaterials with oxidoreductase-like activity offer an appealing way to adjust antiand pro-oxidation in response to biological conditions. To this end, we design and prepare visible light-responsive hybrid nanozymes by combining Au and N-doped carbon dots (Au/NC). It is found that Au/NC can efficiently scavenge reactive oxygen species (ROS) and free radicals and exhibit SOD-like activity, showing intrinsic antioxidant activity. Upon irradiation with visible light, we observe that Au/NC can generate ROS (e.g., hydroxyl radicals, superoxide, and singlet oxygen) and exhibit enhanced oxidase-like activity to accelerate the oxidation of chromogenic substrates, showing pro-oxidant capability. The lightactivated oxidative activity is ascribed to the synergistic effects of photoexcitation of N-doped carbon dots and the surface plasmon resonance of Au nanoparticles. In addition, we demonstrate the application of the anti-and pro-oxidant capability of Au/NC in inhibition or acceleration of oxidation of Monascus pigments and Fe 2+ , which is switched by the incident light. These results will be of significant interest in modulating the biological redox conditions through responsive and precise nanozymes.

Prospects of nano-carbons as emerging catalysts for enzyme-mimetic applications

“…The radicals are responsible for the strong fluorescence emissions centered at 435 nm in the absence of Au/NC, while the emission was reduced in the presence of a catalyst. 118 Furthermore, the synthesis methods can significantly influence the activity of the nano-carbon nanozymes. Herein, Dong et al synthesized the enzyme-like CDs (e-CDs) via the solvothermal method in N , N -dimethylformamide (DMF).…”

“…The mechanism was studied by the generation of • OH with the help of Fenton reagent. The radicals are responsible for the strong fluorescence emissions centered at 435 nm in absence of Au/NC while the emission was reduced in presence of catalyst 118. Further, the synthesis methods can also significantly influence the activity of nano-carbon nanozymes.…”

Semiconductor quantum dots for photodynamic therapy: Recent advances

“…Another recent study using Au gold carbon nano dots (Au/NC) was reported by Zhao et al The Au/NC prepared exhibited superoxide dismutase (SOD) like activity and depleted reactive oxygen species and free radicals in dark. However, on irradiation with visible light, the same Au/NC enhanced the generation of HO·, O 2 − , 1 O 2 and catalyzed the oxidation reactions ( Zhao et al, 2021 ). Thus, smart quantum dots can be designed to induce cell protective and cytotoxic activities, which can be controlled by a light switch.…”

Highly Enhanced Enzymatic Activity of Mn-Induced Carbon Dots and Their Application as Colorimetric Sensor Probes

“…The enzymatic properties of CDs are considerably improved through the formation of hybrids with other materials (e.g., Au, Pd, Fe 3 O 4 , Mn 3 O 4 , and CeO 2 ) [24][25][26][27]. Metal ions (e.g., Mn and Fe) with multiple oxidation states promote the enzymatic activity of CDs [28][29][30][31]. The simple addition of metal ions and chelate molecules to the reaction solution accelerates the enzymatic activity of CDs at a neutral pH [32].…”

“…The simple addition of metal ions and chelate molecules to the reaction solution accelerates the enzymatic activity of CDs at a neutral pH [32]. Doping metal species into a CD framework can act as a catalase mimic and reduce oxidative-stress-related damage on CDs by decomposing H 2 O 2 to H 2 O and O 2 [28]. Metal ions can also influence the formation of CDs and induce variations in the chemical structure of CDs during their synthesis, leading to the enhancement of physicochemical properties [29].…”