Preparation and characterization of AChE immobilized magnetic bio-nanocomposites (Fe₃O₄@Cht/Au) for pesticide detection

Abstract

Free enzymes cause difficulties in many applications due to their insufficient stability, loss of activity in a short time, and most importantly, although they are costly, they are used only once in reactions, lose their effect and cannot be recovered from the environment. Magnetic nanoparticles coated with biocompatible polymeric material are potential candidates for promising enzyme carriers due to their multifunctional pore surfaces, easy removal from the environment provided by the magnetization, ability to main stability under various harsh conditions. This study prepared a biosensor candidate based on the inhibiting acetylcholinesterase enzyme by organophosphate pesticides from chitosan-coated magnetic nanoparticles doped with gold. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction diffractometry, and Fourier transform infrared spectroscopy analysis confirmed the structure of synthesized nanocomposites. Magnetic characteristics of the nanocomposites were assessed using VSM. Bio-nanocomposite (Fe₃O₄@Cht/Au/AChE) was used to determine environmental pollutants qualitatively. Remediation of organophosphate-containing wastewater is an essential issue for environmental sustainability. In this work, Dichlorvos and Chlorpyrifos were selected as organic pollutants to assess the enzymatic activity of immobilized Fe₃O₄@Cht/Au/AChE. Optimum conditions for AChE enzyme were immobilized nanostructures (Fe₃O₄@Cht/Au/AChE) were determined. The optimum pH for the immobilized enzyme was found to be 8, and the optimum temperature was found to be 60 °C. Retained immobilized enzyme activity is found to be around 50% for the 20th reuse. In the presence of 150 µL pesticide, retained immobilized enzyme activity is found to be around 25%. Method validation was performed for pesticides. When using immobilized AChE, the LOD (limit of detection)-LOQ (limit of quantitation) values for Dichlorovos and Chlorpyrifos was obtained in the range of 0.0087–0.029 nM and 0.0014–0.0046 nM, respectively. The relative standard deviation (RSD%) values, which are indicators of precision, were found to be below 2%.

Keywords:

• Fe₃O₄
• chitosan
• Au NPs
• AChE
• pesticides

Author contributions

All authors contributed to the study conception and design. EHÖ: writing, editing, synthesis of nanoparticles, measurement, experimental process, data collection. NKY: writing, measurement, experimental process, formal analysis, synthesis of organic compound and writing analysis. MMK: drafting, conceptualization, editing, and writing. All authors read and approved the final manuscript.

Data availability statement

The data used in the manuscript can be provided upon a reasonable request.

Disclosure statement

The authors have no relevant financial or nonfinancial interests to disclose.

Ethical approval

The authors have no relevant financial or nonfinancial interests to disclose. This research does not involve any human participants or animals. All authors read and approved the final manuscript.