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BACKGROUND: Graphene is an allotrope of carbon with two-dimensional (2D) monolayer honeycombs. A larger detection area and higher sensitivity can be provided by a graphene based nanosenor because of its two-dimensional structure. In addition, owing to its special characteristics including electrical, optical and physical properties, graphene is a known more suitable candidate than other materials for use in sensor applications.
RESULT: In this research, a set of novel models employing field effect transistor (FET) structures using graphene has been proposed and the current–voltage (I-V) characteristics of graphene have been employed to model the sensing mechanism. An adaptive neuro fuzzy inference system (ANFIS) algorithm has been used to provide another model for the current–voltage (I-V) characteristic.
CONCLUSION: It has been observed that the graphene device experiences a large increase in conductance when exposed to Escherichia coli bacteria at 0–104 cfu mL−1 concentrations. Accordingly, the proposed model exhibits satisfactory agreement with the experimental data and this biosensor can detect E. coli bacteria providing high levels of sensitivity.
The discovery of Escherichia coli bacteria in human colon goes back to 1885 and is associated with German bacteriologist Theodor Escherich. He found correlations between particular strains of the bacteria and diarrhoea and gastroenteritis in infants which was a significant finding in the public health area; hence the change of the name of the bacteria from Bacterium Coli to Escherichia Coli in his honor.1,2 It must be noted that most E. coli bacteria do not cause any illness in humans, and some act to the benefit of the human body. However, several E. coli bacteria cause infections that are not gastrointestinal disorders, but rather those of the urinary tract.3,4 In E. coli sensing several biosensor structures have been used, such as optical biosensors, photodiode based sensing,5 integrated waveguide biosensors6 electro-chemical sensing techniques7 – 10 or carbon nanotube biosensors based on a FET structure with very high limits of sensing.11 – 14 Nonetheless, most of these experiments need the use of labels for detection; hence, a simpler method is required. Many of these biosensor fabrications are unmanageable or the limit of sensing is remarkably lower than preferred. Properties and definition of nanomaterials utilized as part of nanobiotechnology for E. coli sensing is recorded in Table 1.
The graphene component shows measureable changes in conductance when in contact with E. Coli, and this behavior is proposed to be used for the detection of this type of bacteria. A bacteria concentration control parameter (?) is introduced in the derivation of the analytical model and is calculated iteratively. The sensor created is label-free, rapid, extremely sensitive and selective for the detection of bacteria E. Coli, with a very low sensing limit of 10 cfu mL−1. Comparison between the results obtained from the analytical and ANFIS models enables more accurate estimations. With the aid of the proposed models, a realistic understanding of the biosensor performance under exposure to E. coli can be gained minimizing the need for empirical experiments.