Umbelliferone as a Small Molecular Peroxidase Mimic towards Sensitive Detection of H2O2 and Glucose

A Novel Ratiometric Cationic Iridium(III) Complex Phosphorescent Probe for Hydrogen Peroxide

A novel cationic iridium(III) complex phosphorescent probe (Ir-BE) containing aromatic boronate ester moiety as recognition unit was designed and synthesized. The probe exhibits ratiometric emission variations (I₄₉₀/I₅₅₀) with the color change from yellow to green only toward H₂O₂ with a broad pH range of 4 - 13. Different from other aromatic boronate-based probes, Ir-BE possesses larger Stokes shift (320 nm) and exhibits good linear correlation (R² = 0.998) between the emission ratio (I₄₉₀/I₅₅₀) and the H₂O₂ concentration in a range of 0 - 300 μM. The detection limit was as low as 0.21 μM. Furthermore, the real water sample studied further proved Ir-BE has excellent selectivity for the quantitative detection of H₂O₂.

Efficient Preservation of Acetylcholinesterase at Room Temperature for Facile Detection of Organophosphorus Pesticide

A simple and inexpensive strategy is reported to facilitate the detection of an organophosphorus pesticide by acetylcholinesterase (AChE). Pullulan is able to preserve AChE at room temperature, but the activity of conserved AChE varies significantly depending on the time, stir and volume of solution to dissolve it. The reason is that AChE entrapped in pullulan tablet remains in an inactive state to avoid denaturalization and deactivation. There is a reactivation process to gradually recover the enzyme activity during dissolution of the tablet. Stirring would interrupt this procedure and lead to a loss of enzyme activity. Dissolution of the tablet for 5 min with a volume of 15 μL could facilitate full recovery of AChE activity. The feasibility of activated AChE for organophosphorus pesticide detection was evaluated using malaoxon. These results contribute to the understanding of preservation mechanism by pullulan and the development of easy-to-use enzyme assays.

Enhanced Mimetic Enzyme Activity of Phosphorylated Porphyrin Nanocomposite Induced by Localized Surface Plasmon Resonance for Colorimetric Assay

Plasmon-enhanced light harvesting has been of great interest to enhance the catalytic efficiency of some composites or hybrids. The enhanced peroxidase-like activity of phosphorylated iron(III) porphyrin (TPPFe(III))-based nanocomposite, induced by localized surface plasmon resonance for a colorimetric assay, was developed in this study. Firstly, a phosphate group modification strategy was adopted to synthesize water-soluble iron(III) porphyrin materials. Then, the as-synthesized TPPFe(III) was covalently attached to core-shell gold nanorods (GNRs), GNR@Au₂S/AuAgS, to form TPPFe(III)-GNR@Au₂S/AuAgS nanocomposite, which shows greatly enhanced peroxidase-like activity compared to TPPFe(III). A mechanism for the enhanced peroxidase-like activity of TPPFe(III)-GNR@Au₂S/AuAgS was proposed, which results from a synergic effect of hot electrons excited by localized surface plasmon resonance and photogenerated electrons of the TPPFe(III), verified by experiments. Furthermore, a fast colorimetric assay for the detection of H₂O₂ and glucose was established based on the unique property of TPPFe(III)-GNR@Au₂S/AuAgS. This colorimetric assay was applied to determine practical human serum samples; satisfactory results demonstrate this method has high accuracy. The present study would not only provide some insights into the mechanism of plasmon-activated enzyme-like reactions, but also offer new strategies for improving the catalytic activity of a mimetic enzyme.