Fabrication of Gold Nanoparticle Incorporated Bimetallic Metal Organic Framework Electrode for Direct, Sensitive and Selective Detection of Ochratoxin A from Food Samples

Ochratoxin A (OTA) is a type of mycotoxin produced by fungi as its secondary metabolite. This mycotoxin contaminates the food by its presence and is a significant global threat to animal and human health, necessitating rapid, sensitive and selective detection methods. This study introduces an electrochemical sensor using gold nanoparticle (AuNP) incorporated bimetallic metal organic framework (MOF; Fe₂Zn-MIL88B) nanocomposite to selectively detect OTA in the presence of other competing mycotoxins and food samples. UV–VIS spectrophotometer and HR-TEM analysis have confirmed the successful incorporation of AuNPs within the Fe₂Zn-MIL88B structure. The presence of AuNPs within the MOF structure (AuNP-Fe₂Zn-MIL88B/MWCNT@GCE) has demonstrated a two-fold enhancement in the electrochemical oxidative response of OTA. The ideal AuNP and Fe₂Zn-MIL88B MOF ratio to catalyze OTA was identified as 4 : 1 (v : v). Under optimized detection conditions, the bimetallic MOF electrode had a two-fold OTA catalytic property as compared to the individual metal-ions (Fe or Zn) MOF electrodes (Fe-MIL88B/MWCNT/GCE and Zn-MIL88B/MWCNT/GCE). Our sensor has exhibited remarkable selectivity to OTA in the presence of two other co-existing mycotoxins (patulin and aflatoxin B1), a limit of detection (LOD) of 4.63 ng/mL, excellent reproducibility (RSD = 2.29%) and stable up to 4 months. AuNP-Fe₂Zn-MIL88B/MWCNT@GCE has efficiently detected OTA between 4 - 35 °C and in OTA spiked food samples (red chili, coffee beans, corn, wheat, rice and almonds) with a satisfactory recovery rate of 85 – 112 %. Hence, the developed sensor AuNP-Fe₂Zn-MIL88B/MWCNT@GCE offers a simple solution for efficient OTA detection that holds significant potential to ensure food safety and mitigate the associated health risks.