Metal-phenolic networks derived CN-FeC hollow nanozyme with robust peroxidase-like activity for total antioxidant capacity detection

A tannate-iron network-derived peroxidase-like catalyst loaded with Fe ions on carbon nitride (C3N4) was reported for detection of total antioxidant capacity (TAC) in food in this study. Metal-phenolic networks (MPNs) was employed to form a low coordination compound on C3N4, and calcined catalyst formed hollow structure with abundant and uniform Fe sites and surface folds. CN-FeC exhibited significant peroxidase-like activity and high substrate affinity. The homogeneous distribution of amorphous Fe elements on the C3N4 substrate provides more active sites, resulting in provided excellent catalytic activity to activate H2O2 to ·OH, 1O2 and O2·-. The established CN-FeC/TMB/H2O2 colorimetric system can detect AA in the concentration range of 5-40 μM, with the detection limits of 1.40 μM, respectively. It has good accuracy for the detection of vitamin C tablets, beverages. Taken together, this work shows that metal-phenolic networks can be an effective way to achieve efficient utilization of metal atoms and provides a promising idea for metal-phenolic networks in nanoparticle enzyme performance enhancement.

Iron-Imprinted Single-Atomic Site Catalyst-Based Nanoprobe for Detection of Hydrogen Peroxide in Living Cells

Fe-based single-atomic site catalysts (SASCs), with the natural metalloproteases-like active site structure, have attracted widespread attention in biocatalysis and biosensing. Precisely, controlling the isolated single-atom Fe-N-C active site structure is crucial to improve the SASCs' performance. In this work, we use a facile ion-imprinting method (IIM) to synthesize isolated Fe-N-C single-atomic site catalysts (IIM-Fe-SASC). With this method, the ion-imprinting process can precisely control ion at the atomic level and form numerous well-defined single-atomic Fe-N-C sites. The IIM-Fe-SASC shows better peroxidase-like activities than that of non-imprinted references. Due to its excellent properties, IIM-Fe-SASC is an ideal nanoprobe used in the colorimetric biosensing of hydrogen peroxide (H₂O₂). Using IIM-Fe-SASC as the nanoprobe, in situ detection of H₂O₂ generated from MDA-MB-231 cells has been successfully demonstrated with satisfactory sensitivity and specificity. This work opens a novel and easy route in designing advanced SASC and provides a sensitive tool for intracellular H₂O₂ detection.

DNA-mediated inhibition of peroxidase-like activities on platinum nanoparticles for simple and rapid colorimetric detection of nucleic acids

In this research, we found that the peroxidase-like activities of noncovalent DNA-Pt hybrid nanoparticles could be obviously blocked, when Pt nanoparticles (PtNPs) were synthesized in situ using DNA as a template. Moreover, this self-assembled synthetic process was very convenient and rapid (within few mintues), and the inhibition mediated by DNA was also very effective. First, by the paper-based analytical device (PAD) we found the catalytic activities of DNA-Pt hybrid nanoparticles exhibited a linear response to the concentration of DNA in the range from 0.0075 to 0.25µM. Then, with the magnetic bead isolated system and target DNA-induced hybridization chain reaction (HCR), we realized the specific target DNA analysis with a low detection of 0.228nM, and demonstrated its effectivity in distinguishing the target DNA from other interferences. To our knowledge, this is the first report that used the nanoassembly between DNA and PtNPs for colorimetric detection of nucleic acids, which was based on DNA-mediated inhibition of catalytic activities of platinum nanoparticles. The results may be useful for understanding the interactions between DNA and metal nanoparticles, and for development of other convenient and effective analytical strategies.