Study on Development of Piezoelectric Immunosensor for Aflatoxin b1 Detection based on Nanostructured Thin Films

Abstract

Aflatoxin B1 (AFB1), a potent carcinogenic mycotoxin, is of great concern due to their frequent occurrence in foods. The immunosensors offer a tremendous potentiality for a real time, smart, reliable and portable sensing strategy for AFB1. A simple, label free electrochemical quartz crystal microbalance(EQCM) based immunosensor using monoclonal Aflatoxin B1 antibody (aAFB1) realized on self assembled monolayer(SAM) of 4-amino thio phenol(4-ATP) on gold coated quartz crystal(BSA/aAFB1/4-ATP/Au) is developed to detect AFB1 within a linear range from 0.1 to 4 ngmL-1 with LOD of 0.08 ngmL-1 and high sensitivity of 532.7 and#956;A ng-1mLcm-2 [1,2]. To further enhance immuno response two strategies are employed (i) increased electron transfer rate by inclusion of gold nano particles(AuNP) and (ii) to follow a competitive sandwich protocol via metal nano particle-secondary antibody hybrid system. In the first approach, a multi layered immunoelectrode is designed by SAM of hexane dithiol (HDT), 3D layer of gold nano particles, SAM layer of cysteamine (AuNPs), covalently linked aAFB1 antibody and finally BSA to produce BSA/aAFB1/Cys/AuNP/HDT/Au immuno sensor. The immunosensor detects AFB1 within a linear range from 0.008 to 10 ngmL-1 with an ultra LOD of 8 pg mL-1[3]. In the second approach, a competitive sandwiched EQCM magneto immunosensor is fabricated using Au coated iron oxide core shell nano structure- poly clonal antibody conjugate(r-IgG-Au-Fe3O4) bioconjugate. The linear range of AFB1/BSA/aAFB1/4-ATP/Au immunosensor lay within from 0.05-5 ngmL-1 with a LOD of 0.04 ngmL-1 and sensitivity of 335.7 and#956;A ng-1mLcm-2[4]. The unique feature of the immunosensor is its regeneration up to 15-16 times with 2-3% loss in activity using a strong external magnet. The BSA/aAFB1/4-ATP/Au immunoelectrode is successfully utilized to detect AFB1 in contaminated groundnuts extract with the minimum error which is in agreement with the LC-MS/MS results. newline