Label-Free and Ultrasensitive Detection of Butyrylcholinesterase and Organophosphorus Pesticides by Mn(II)-Based Electron Spin Resonance Spectroscopy with a Zero Background Signal

Abstract

Mn(II)-based electron spin resonance (ESR) spectroscopy was used for detecting butyrylcholinesterase (BChE) and organophosphorus pesticides (OPs). MnO2 nanosheets were synthesized with manganese chloride and hydrogen peroxide. With the catalysis of BChE, S-butyrylthiocholine iodide (BTCh) was hydrolyzed into thiocholine which has a reducing −SH group. In the presence of thiocholine, MnO2 nanosheets were broken down and Mn(IV) in MnO2 nanosheets was reduced into Mn(II). Mn2+ is a paramagnetic ion and gives a good ESR signal. In contrast, MnO2 nanosheets have no ESR signal and need not be separated from Mn2+. Mn2+ can be determined directly by ESR spectroscopy, and no further sensing probe is needed. ESR spectroscopy based on directly detecting Mn2+ is much simpler than those using other probes besides MnO2. The ESR signal of Mn2+ is proportional to the catalytic activity of BChE. OPs which inhibit the activity of BChE can also be detected by probing the ESR signal of Mn2+. Since there is no ESR signal of MnO2 nanosheets, the background signal in the absence of BChE was close to zero. The limit of detection (LOD) of BChE was as low as 0.042 U L–1. The standard curve for determining the OP paraoxon was established by measuring the inhibition of BChE by paraoxon, and the LOD of paraoxon was found to be 0.076 ng mL–1. The spiked Chinese cabbage extract samples were analyzed, and the experimental results indicated that the recoveries were from 96.5 to 102.8%. The planted Chinese cabbage was sprayed with the paraoxon solution, and the residue amount of paraoxon in the extract was estimated by the method. The result obtained by the present method was consistent with that obtained by HPLC, which proved the practicability of this new method.

The role of Mn in widening the potential window of solid solution derived electrodes for aqueous supercapacitors

“…In contrast, Mn 3+ with a low spin state without a lone pair of electrons (3d 4 ) generally shows no ESR signal. 34 As shown in Fig. S5, † the np-NiO(MnO x )@Ni-5 electrode shows an obvious Mn 4+ single intense ESR signal, which may be attributed to the Mn 4+ in the low-symmetry crystal eld (Mn 4+ -lscf).…”

Three–Four Photon Transition Mn(II) Complex Monitoring Lysosome-Related ATP in Real Time via Fluorescence Lifetime Imaging

“…At present, the colorimetric method and fluorescent probe are commonly reported for detecting biomolecules. Compared with the colorimetric method, which has low sensitivity and is easily interfered, fluorescent probes stand out for their high sensitivity and excellent in situ imaging ability. − What is more is that it is notable that higher order multiphoton probes with near-infrared excitation show less photodamage and longer penetration depth. Because the excitation efficiency of higher order nonlinear behavior is limited, a high concentration of fluorescent dyes, which may cause molecular aggregation, leading to fluorescence quenching, is usually required to overcome this defect .…”

A Programmable Microfluidic Paper-Based Analytical Device for Simultaneous Colorimetric and Photothermal Visual Sensing of Multiple Enzyme Activities

“…8 reactions encompassing both cholinesterase and noncholinesterase compounds. 9 The ALP and BChE biomarkers have been clinically recognized as crucial indicators for the identification of liver disorders, including cirrhosis, hepatic impairment, and chronic hepatitis. 10,11 Moreover, aberrant ALP and BChE levels in the bloodstream have been closely associated with diabetes, hypertension, hyperthyroidism, and malignant tumors.…”

“…Enzymes, as crucial biocatalysts, are omnipresent in living organisms and actively participate in diverse physiological regulatory processes for maintaining normal bodily functions. , The physiological functionalities of enzymes in vivo are intricately intertwined with their expression levels, and abnormal enzyme activities generally serve as a pivotal indicator for clinical diagnosis of various diseases. , Among these crucial enzymes, alkaline phosphatase (ALP) functions as a hydrolase to facilitate the dephosphorylation of proteins, nucleic acids, and other biomolecules . Meanwhile, butyryl cholinesterase (BChE) is involved in nonspecific hydrolysis reactions encompassing both cholinesterase and noncholinesterase compounds . The ALP and BChE biomarkers have been clinically recognized as crucial indicators for the identification of liver disorders, including cirrhosis, hepatic impairment, and chronic hepatitis. , Moreover, aberrant ALP and BChE levels in the bloodstream have been closely associated with diabetes, hypertension, hyperthyroidism, and malignant tumors. , Therefore, the simultaneous, facile, and accurate determination of ALP and BChE activities in blood is of paramount significance and urgency for the early diagnosis and prognosis of the associated diseases.…”