Atomically Dispersed Manganese on Graphene Nanosheets as Biocompatible Nanozyme for Glutathione Detection in Liver Tissue Lysate Using Microfluidic Paper-based Analytical Devices

Development of a novel ternary MOF nanozyme-based smartphone-integrated colorimetric and microfluidic paper-based analytical device for trace glyphosate detection

Given the significant and potential fatal implications of glyphosate (GLY) residues on human health and the integrity of ecosystems, their presence has garnered substantial global concern and scrutiny. Herein, we introduced a pioneering colorimetric sensing platform, the first of its kind, based on ternary metal-organic frameworks (ZnCo-ZIFs@MIL-101(Fe)). This innovative platform enabled ultra-sensitive, affordable, portable and rapid on-site detection of GLY. This platform achieved a wider linear range for GLY of 0.02-40 μg/mL with an exhibiting remarkable detection limit of 1 ng/mL, which was attributed to the electronic hybridization of the Fe3+, Co2+, and Zn2+ metal centers of ZnCo-ZIFs@MIL-101(Fe), significantly enhancing the composite's catalytic performance. The assay was successfully employed to detect GLY in food and herb samples. Moreover, to meet the demand of in-field detection for GLY, a smartphone detection method based on ZnCo-ZIFs@MIL-101(Fe) with visual, intelligent, and portable features was fabricated. This detection concentration range of GLY was 0-1 μg/mL, and the limit of smartphone detection was 23 ng/mL. Furthermore, this sensor seamlessly integrated with smartphones and paper-based microfluidic chips (μPADs), which constructed a portable test strips-smartphone sensing platform for facilitating real-time and on-site visual quantitative detection of GLY. The detection concentration range was 0-1 μg/mL, and the limit was calculated as low as 75 ng/mL. The assay was highly adaptable in practical applications. In summary, our study paved a novel pathway for the design and utilization of multi-metal MOF nanozymes in on-site pesticide monitoring.

A facile colorimetric sensor for ketoprofen detection in milk: Integrating molecularly imprinted polymers with Cu-doped Fe3O4 nanozymes

A facile and efficient detection method is required to address the potential health risks of ketoprofen (KP) in animal-derived foods. Herein, we integrated molecularly imprinted polymers (MIPs) with Cu-doped Fe3O4 nanozymes (Fe3O4-Cu) to develop a selective colorimetric sensor for KP detection. Chitosan and glutaraldehyde were used as functional monomers and cross-linkers to fabricate proposed the MIPs@Fe3O4-Cu. On KP addition, it was specifically captured by the imprinted cavities, thereby blocking the channels between chromogenic substrates and Fe3O4-Cu. Based on this rationale, a selective colorimetric sensor utilizing MIPs@Fe3O4-Cu was established, exhibiting a linear range of 0.25-100 μM and a detection limit of 0.073 μM. The developed method was validated through its application in milk samples, yielding satisfactory recoveries with low relative standard deviations. This efficient and selective colorimetric sensor holds immense significance for KP detection in complex samples.

Based on Fe and Ni prepared organic colloidal materials as efficient oxide nanozymes for chemiluminescence detection of GSH and Hg(II) ions

Metal-organic gels (MOGs) are a type of metal-organic colloid material with a large specific surface area, loose porous structure, and open metal active sites. In this work, FeNi-MOGs were synthesized by the simple one-step static method, using Fe(III) and Ni(II) as the central metal ions and terephthalic acid as the organic ligand. The prepared FeNi-MOGs could effectively catalyze the chemiluminescence of luminol without the involvement of H2O2, which exhibited good catalytic activity. Then, the multifunctional detected platform was constructed for the detection of GSH and Hg2+, based on the antioxidant capacity of GSH, and the strong affinity between mercury ion (Hg2+) and GSH which inactivated the antioxidant capacity of GSH. The experimental limits of detection (LOD) for GSH and Hg2+ were 76 nM and 210 nM, and the detection ranges were 2-100 μM and 8-4000 μM, respectively. The as-proposed sensor had good performance in both detection limit and detection range of GSH and Hg2+, which fully met the needs of daily life. Surprisingly, the sensor had low detection limits and an extremely wide detection range for Hg2+, spanning five orders of magnitude. Furthermore, the detection of mercury ions in actual lake water and GSH in human serum showed good results, with recovery rates ranging from 90.10 % to 105.37 %, which proved that the method was accurate and reliable. The as-proposed sensor had great potential as the platform for GSH and Hg2+ detection applications.

Tailoring the peroxidase-like properties of Mo atom nanoclusters/N-MXene nanozymes for sensitive colorimetric detection of glutathione

Although nanozyme engineering has made tremendous progress, there is a huge gap between them and natural enzymes due to the enormous challenge of precisely adjusting the geometric and electronic structure of active sites. Considering that intentionally adjusting the metal-carrier interactions may bring the promising catalytic activity, in this work, a novel Mo atom nanocluster is successfully synthesized using nitrogen-doped Mxene (MoACs/N-MXene) nanozymes as carriers. The constructed MoACs/N-MXene displays excellent peroxidase-like catalytic activity and kinetics, outweighing its N-MXene and Mo nanoparticles (NPs)-MXene references and natural horse radish peroxidase. This work not only reports a successful example of MoACs/N-MXene nanozyme as a guide for achieving peroxidase-mimic performance of nanozymes for colorimetric glutathione sensing at 0.29 μM, but also expands the application prospects of two-dimensional MXene nanosheets by reasonably introducing metal atomic clusters and nonmetal atom doping and exploring related nanozyme properties.

[2+1] Cycloadditions Modulate the Hydrophobicity of Ni-N4 Single-Atom Catalysts for Efficient CO2 Electroreduction

Microenvironment regulation of M-N4 single-atom catalysts (SACs) is a promising way to tune their catalytic properties toward the electrochemical CO2 reduction reaction. However, strategies that can effectively introduce functional groups around the M-N4 sites through strong covalent bonding and under mild reaction conditions are highly desired. Taking the hydrophilic Ni-N4 SAC as a representative, we report herein a [2+1] cycloaddition reaction between Ni-N4 and in situ generated difluorocarbene (F2C:), and enable the surface fluorocarbonation of Ni-N4, resulting in the formation of a super-hydrophobic Ni-N4-CF2 catalyst. Meanwhile, the mild reaction conditions allow Ni-N4-CF2 to inherit both the electronic and structural configuration of the Ni-N4 sites from Ni-N4. Enhanced electrochemical CO2-to-CO Faradaic efficiency above 98 % is achieved in a wide operating potential window from -0.7 V to -1.3 V over Ni-N4-CF2. In situ spectroelectrochemical studies reveal that a highly hydrophobic microenvironment formed by the -CF2- group repels asymmetric H-bonded water at the electrified interface, inhibiting the hydrogen evolution reaction and promoting CO production. This work highlights the advantages of [2+1] cycloaddition reactions on the covalent modification of N-doped carbon-supported catalysts.

"Three-in-One" Plasmonic Au@PtOs Nanocluster Driven Lateral Flow Assay for Multimodal Cancer Exosome Biosensing

Exploiting the multiple properties of nanozymes for the multimode lateral flow assay (LFA) is urgently required to improve the accuracy and versatility. Herein, we developed a novel plasmonic Au nanostar@PtOs nanocluster (Au@PtOs) as a multimode signal tag for LFA detection. Based on the PtOs bimetallic nanocluster doping strategy, Au@PtOs can indicate both excellent SERS enhancement and nanozyme catalytic activity. Meanwhile, Au@PtOs displays a better photothermal effect than that of Au nanostars. Therefore, catalytic colorimetric/SERS/temperature three-mode signals can be read out based on the Au@PtOs nanocomposite. The Au@PtOs was combined with LFA and applied for breast cancer exosome detection. The detection limit for the colorimetric/SERS/temperature mode was 2.6 × 103/4.1 × 101/4.6 × 102 exosomes/μL, respectively, which was much superior to the common Au nanoparticles LFA (∼105 exosomes/μL). Moreover, based on the fingerprint molecular recognition ability of the SERS mode, exosome phenotypes derived from different breast cancer cell lines can be discriminated easily. Based on the convenient visual colorimetric mode and sensitive SERS/temperature quantitative modes, Au@PtOs driven LFA can satisfy the requirements of accurate and flexible multimodal sensing in different application scenarios.

Ag-Cu filled nanonets with ultrafine dual-nanozyme active units for neurotransmitter biosensing

Ag and Cu based nanostructures serve as advanced functional materials for biomedical applications, due to their unique properties. Here, we proposed a novel neurotransmitter biosensing method based on Ag-Cu composite nanozyme, synthesized through the soft film plate method. Supported by the soft film template, the Ag-Cu nanozymes were stably kept to an ultrafine 2D structure with high monodispersity, which provided a large specific surface area and sufficient binding sites, leading to controllable and improved dual-nanozyme activities over similar-sized mono-Ag and mono-Cu, and up to 4.95 times of natural enzyme-level. The multi-path enzymatic reaction processes catalyzed by Ag-Cu composite nanozymes were firstly theoretically discussed in detail, according to the theoretical redox potential of redox couples in the reaction systems. On this basis, the Ag-Cu filled nanonets based neurotransmitter biosensing is successfully applied in rapid detection for glutathione and dopamine, possessing a linear range of 10∼100 μM and 1-10 μM, and a detection limit of 3.01 μM and 0.29 μM, respectively, which exhibited superior performance for biomedical purposes over most commercially available products in speed and precision.