Identification of frozen/thawed beef based on label-free detection of hemin (Iron Porphyrin) with solution-gated graphene transistor sensors

The fraud labeling of frozen/thawed meat as fresh meat has become one of the severe problems in the current meat products market. Hemin, as a highly bioavailable iron form in beef, loses with exudates during freezing and thawing cycles. Based on this fact, in this work, solution-gated graphene transistor (SGGT) devices were constructed for discrimination of frozen/thawed beef. The detection mechanism of the sensor is mainly attributed to the adsorption of hemin molecules on the surface of graphene through phi-phi interaction, which leads to the change of doping level of graphene. The SGGT sensor for hemin shows a very low detection limit of 10 nM and a linear range of 100 nM 10 mu M. Finally, determination of the number of freezing and thawing cycles by the rate of hemin loss detected by SGGT sensors for actual beef samples was successfully demonstrated.