Facile Synthesis of Enzyme-Inorganic Hybrid Nanoflowers and Its Application as a Colorimetric Platform for Visual Detection of Hydrogen Peroxide and Phenol

This study reports a facile approach for the synthesis of horseradish peroxidise (HRP)-inorganic hybrid nanoflowers by self-assembly of HRP and copper phosphate (Cu₃(PO₄)₂·3H₂O) in aqueous solution. Several reaction parameters that affect the formation of the hybrid nanoflowers were investigated and a hierarchical flowerlike spherical structure with hundreds of nanopetals was obtained under the optimum synthetic conditions. The enzymatic activity of HRP embedded in hybrid naonflowers was evaluated based on the principle of HRP catalyzing the oxidation of <i>o</i>-phenylenediamine (OPD) in the presence of hydrogen peroxide (H₂O₂). The results showed that 506% enhancement of enzymatic activity in the hybrid nanoflowers could be achieved compared with the free HRP in solution. Taking advantages of the structural feature with catalytic property, a nanoflower-based colorimetric platform was newly designed and applied for fast and sensitive visual detection of H₂O₂ and phenol. The limits of detection (LODs) for H₂O₂ and phenol were as low as 0.5 μM and 1.0 μM by the naked-eye visualization, which meet the requirements of detection of both analytes in clinical diagnosis and environmental water. The proposed method has been successfully applied to the analysis of low-level H₂O₂ in spiked human serum and phenol in sewage, respectively. The recoveries for all the determinations were higher than 92.6%. In addition, the hybrid nanoflowers exhibited excellent reusability and reproducibility in cycle analysis. These primary results demonstrate that the hybrid nanoflowers have a great potential for applications in biomedical and environmental chemistry

Protein-Metal Organic Framework Hybrid Composites with Intrinsic Peroxidase-like Activity as a Colorimetric Biosensing Platform

Artificial enzyme mimetics have received considerable attention because natural enzymes have some significant drawbacks, including enzyme autolysis, low catalytic activity, poor recovery, and low stability to environmental changes. Herein, we demonstrated a facile approach for one-pot synthesis of hemeprotein-metal organic framework hybrid composites (H-MOFs) by using bovine hemoglobin (BHb) and zeolitic imidazolate framework-8 (ZIF-8) as a model reaction system. Surprisingly, the new hybrid composites exhibit 423% increase in peroxidase-like catalytic activity compared to free BHb. Taking advantages of the unique pore structure of H-MOFs with high catalytic property, a H-MOFs-based colorimetric biosensing platform was newly constructed and applied for the fast and sensitive detection of hydrogen peroxide (H₂O₂) and phenol. The corresponding detection limits as low as 1.0 μM for each analyte with wide linear ranges (0–800 μM for H₂O₂ and 0–200 μM for phenol) were obtained by naked-eye visualization. Significantly, a sensitive and selective method for visual assay of trace H₂O₂ in cells and phenol in sewage was achieved with this platform. The stability of H-MOFs was also examined, and excellent reproducibility and recyclability without losing in their activity were observed. In addition, the general applicability of H-MOFs was also investigated by using other hemeproteins (horseradish peroxidase, and myoglobin), and the corresponding catalytic activities were 291% and 273% enhancement, respectively. This present work not only expands the application of MOFs but also provides an alternative technique for biological and environmental sample assay

Additional file 1 of A potent synthetic nanobody with broad-spectrum activity neutralizes SARS-CoV-2 virus and the Omicron variant BA.1 through a unique binding mode

Additional file 1: Table S1. Epitope binning of spike nanobodies. Table S2. Cryo-EM data collection, refinement and validation statistics. Table S3. Conservation of epitopic residues in RBD for C5G2 binding from natural occurring SARS-Cov-2 variants