Graphene Quantum Dots as Nanozymes for Electrochemical Sensing of Yersinia enterocolitica in Milk and Human Serum

Abstract

The genus <i>Yersinia</i> contains three well-recognized human pathogens, including <i>Y. enterocolitica</i>, <i>Y. pestis</i>, and <i>Y. pseudotuberculosis</i>. Various domesticated and wild animals carry <i>Yersinia</i> in their intestines. Spread to individuals arises from eating food or water contaminated by infected human or animal faeces. Interaction with infected pets and domestic stock may also lead to infection. <i>Yersinia</i> is able to multiply at temperatures found in normal refrigerators; hence, a large number of the bacteria may be present if meat is kept without freezing. <i>Yersinia</i> is also rarely transmitted by blood transfusion, because it is able to multiply in stored blood products. Infection with <i>Yersinia</i> can cause yersiniosis, a serious bacterial infection associated with fever, abdominal pain and cramps, diarrhea, joint pain, and symptoms similar to appendicitis in older children and adults. This paper describes a novel immunosensor approach using graphene quantum dots (GQDs) as enzyme mimics in an electrochemical sensor set up to provide an efficient diagnostic method for <i>Y. enterecolitica</i>. The optimum assay conditions were initially determined and the developed immunosensor was subsequently used for the detection of the bacterium in milk and human serum. The GQD-immunosensor enabled the quantification of <i>Y. enterocolitica</i> in a wide concentration range with a high sensitivity (LOD_milk = 5 cfu mL^-1 and LOD_serum = 30 cfu mL^-1) and specificity. The developed method can be used for any pathogenic bacteria detection for clinical and food samples without pre-sample treatment. Offering a very rapid, specific and sensitive detection with a label-free system, the GQD-based immunosensor can be coupled with many electrochemical biosensors.