Detection of Aristolochic Acid Using a Piezoelectric Immunosensor Based on Magnetic Carbon Nanocomposites

Abstract

This article describes a method for detection of aristolochic acid (AA) in food products using a piezoelectric immunosensor, the recognition layer of which was magnetic carbon nanocomposites (MCNCs) with AA protein conjugates immobilized on their surface. Methods for the synthesis of magnetic Fe₃O₄ nuclei and their fixation on the surface of multiwalled carbon nanotubes (CNTs) have been studied. Using IR spectroscopy, it was established that the formation of the recognition layer of the sensor occurs owing to the formation of covalent bonds between the amino groups of AA conjugates and the carboxyl groups of CNTs. The concentrations of protein conjugates based on ovalbumin (OVA) and bovine serum albumin (BSA) (0.3 and 0.2 mg/mL) and the degree of dilution of antibodies (0.25) providing optimal characteristics of the piezoelectric immunosensor were determined. The metrological characteristics of the determination of AA using the proposed method have been established: the range of determined contents and the detection limit of AA when using a piezoelectric immunosensor with a recognition layer based on MCNC/AA-OVA and MCNC/AA-BSA are 50–400 and 10 ng/mL and 100–300 and 50 ng/mL, respectively. The sensor was tested upon determination of AA in samples of Chinese herbal tea and dietary supplements for weight loss. No acid was found in the tea, but in the dietary supplements, its content is 3.2 μg/g.