Comparison of reduced graphene oxide and Multi-WalledCarbon Nanotubes modifications on glassy carbon electrode forEscherichia coli detection

Background and Aim : Escherichia coli is an indicator in the quality control of pharmaceuticaland other samples. This study was aimed to compare the classical methods and biosensors for E.coli detection.Methods : A reference electrode (Azar Ag/AgCl electrode), a counter electrode (platinum wire),and a glassy carbon electrode as working electrode were used for E. coli detection. Reducedgraphene oxide (rGO) which synthesized with modified Hammer method and also Multi-WalledCarbon Nanotubes (MWCNTs) were immobilized on glassy carbon electrode (GCE) separately.Then, AuNPs decorated on them with chronoamperometric and reduction method and activatedwith the mixture of ۵ mM N-hydroxysuccinimide (NHS) and ۲ mM ۱-ethyl-۳-(۳-dimethylaminopropyl) carbodiimide hydrochloride (EDC) at ۳۳°C for ۲ h. Then, they wereexposed to polyclonal E. coli antibody for ۱ hour at ۳۳°C. After washing with PBS )pH ۷.۴( anddrying, ۵ μl of ۰.۵ W/V% Bovine Serum Albumin solution was immediately immobilized on themodified electrode. Morphology and structure of rGO and MWCNTs and AuNPs were verified bySEM as well as the surface of bare glassy carbon electrode before and after modification. Square-Wave Voltammetric and Cyclic Voltammetric techniques were used for detection of E. coli indifferent samples. On the other hand, for classic method, serial dilutions of E. coli ATCC ۸۷۳۹were prepared and cultured on Tryptic Soy Agar and incubated at ۳۷oC for ۷۲ hours. Results werecompared with biosensor detections. Salmonella enterica ATCC ۱۴۰۲۸, Pseudomonas aeroginosaATCC ۹۰۲۷, Bacillus subtilis ATCC۶۶۳۳ and Staphylococcus aureus ATCC ۶۵۳۸ referencestrains were used for examining the specificity of the optimized electrode.Results : GC/rGO/AuNPs/BSA modification had not significant change in currents in comparewith GC/MWCNTs/AuNPs/BSA. There was similar sensitivity of detection in polluted samplesin compare with plate method. LOD of biosensor with GC/MWCNTs/AuNPs/BSA was about ۳.۰۲CFU/ml without interference with other bacteria.Conclusion : In spite of two methods of AuNPs immobilization, SEM pictures established thatcurrent deviation with Au was not applicable in GC/rGO/AuNPs/BSA modification. Presence ofMWCNTs with AuNPs could effect on spread of electrode area and conductivity. There was nosignificant deviation between classical and biosensor analysis.

کلیدواژه ها:

Reduced graphene oxide ، Biosensor ، E. coli ، Multi-Walled Carbon Nanotubes ، AuNPs