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

Abstract

Nanomaterial-based enzyme mimetics (nanozymes) have attracted significant interest because of their lower cost and higher stability compared to natural enzymes. In this study, we focused on improving the enzymatic properties of metal induced N-doped carbon dots (N-CDs), which are nanozymes of interest, and their applications for sensory systems. For this purpose, Mn(acetate)2 was introduced during the synthetic step of N-doped carbon dots, and its influence on the enzymatic properties of Mn-induced N-CDs (Mn:N-CDs) was investigated. Their chemical structure was analyzed through infrared spectroscopy and X-ray photoelectron spectrometry; the results suggest that Mn ions lead to the variation in the population of chemical bonding in Mn:N-CDs, whereas these ions were not incorporated into N-CD frameworks. This structural change improved the enzymatic properties of Mn:N-CDs with respect to those of N-CDs when the color change of a 3,3′,5,5′-tetramethylbenzidine/H2O2 solution was examined in the presence of Mn:N-CDs and N-CDs. Based on this enhanced enzymatic property, a simple colorimetric system with Mn:N-CDs was used for the detection of γ-aminobutyric acid, which is an indicator of brain-related disease. Therefore, we believe that Mn:N-CDs will be an excellent enzymatic probe for the colorimetric sensor system.

Intrinsic Multienzyme-like Activities of the Nanoparticles of Mn and Fe Cyano-Bridged Assemblies

“…Interest in investigating the catalytic properties of manganese complexes is due to their essential role in redox biology with regard to the composition of antioxidant enzymes: manganese-containing catalases, mitochondrial manganese superoxide dismutase (MnSOD), and manganese peroxidase, as well as a variety of Mn oxidation states that are favorable for (electro)catalytic activities. Moreover, Mn complexes are known for their high catalytic activity and protective role in (electro)chemical reactions with dioxygen and ROS [14,[35][36][37][38][39][40]. Recently, Mn-doped PB nanoparticles were used in a biological environment as efficient agents in photothermal therapy [41] and MR imaging [42].…”

Zn-assisted modification of the chemical structure of N-doped carbon dots and their enhanced quantum yield and photostability

“…Zn:N-CD was prepared as reported previously with some modifications. 38,39 Zn(OAc)2 was added to the reaction solution containing CA and EDA (Figure 1a). The synthesized Zn:N-CD was confirmed to have a spherical shape and an average size of Please do not adjust margins Please do not adjust margins 3.5 ± 1.1 nm, as shown in the TEM image (Figure 1b).…”

“…Zn:N-CD was prepared as reported previously with some modications. 38,39 Zn(OAc) 2 was added to the reaction solution containing CA and EDA (Fig. 1a).…”

“…N-CDs and Zn:N-CDs were prepared according to a previously reported method with some modifications. 38,39 In a typical synthesis, CA (10 μmol), and EDA (5 μmol) were dissolved in deionized water (15 mL) for both N-CD and Zn:N-CDs. Zn(OAc)2 (0.1-5 μmol) is further added for Zn:N-CDs, and the resulting mixture was hydrothermally treated in a Teflon-lined stainless steel autoclave at 200 °C.…”

“…N-CDs and Zn:N-CDs were prepared according to a previously reported method with some modications. 38,39 In a typical synthesis, CA (10 mmol) and EDA (5 mmol) were dissolved in deionized water (15 mL) for both N-CD and Zn:N-CDs. Zn(OAc) 2 (0.1-5 mmol) is further added for Zn:N-CDs, and the resulting mixture was hydrothermally treated in a Teon-lined stainless steel autoclave at 200 C. Aer one hour of the reaction, the mixture was cooled to room temperature, and the residue was puried by column chromatography (CombiFlash NextGen 100, Teledyne ISCO) to obtain a brown Zn:N-CD sample.…”