Development of an ultrasensitive electrochemical aptasensor based on aptamer/rGO/SPGE for the detection of Botulinum neurotoxin A (BoTN/A) in food samples

Consumption of Botulinum neurotoxin A (BoTN/A) contaminated foods has increased the public health issues which necessitates the development of rapid and simple diagnostic tools for their sensitive detection. Electrochemical aptasensors can replace existing biosensors and traditional methods of BoTN/A detection in foods. These aptasensors are simple, quick response, economic, precise, sensitive, accurate and reproducible. In the present study, an electrochemical aptasensor was constructed by immobilizing BoTN/A specific aptamer and reduced graphene oxide (rGO) onto screen printed gold electrode (SPGE) for the detection of BoTN/A in spiked food samples. The specificity of this aptasensor was achieved by conjugating BoTN/A specific aptamer on rGO/ SPGE. Test sample containing BoTN/A form aptamer-BoTN/A complex onto SPGE which was directly proportional to BoTN/A concentration. Formation of aptamer-BoTN/A complex reduced the surface of working SPGE for redox reactions. Thus decreased the current peaks that was taken as measuring signal of BoTN/A in test food sample. BoTN/A aptasensor showed optimum response at pH 6.5 and 30 degrees C temperature. The responsetime of BoTN/A/aptamer/rGO/SPGE was 6 s. In optimum conditions aptamer/rGO/SPGE BoTN/A aptasensor exhibited wide linearity ranges from 1-100 pM and 1 pM limit of detection (LOD). The analytical recoveries of aptamer/ rGO/SPGE BoTN/A aptasensor at 5 pM and 10 pM BoTN/A were 98.5 % and 99.8 % respectively. The proposed aptasensor showed unique sensitivity, reproducibility and accuracy. Moreover, aptamer/rGO/SPGE aptasensor was used for the detection of BoTN/A in five different types of food samples.