Aptamer based electrochemical biosensor design for clinical analysis

In this work, an aptamer-based nanobiosensor for cancer cell detection was developed. A composite nanofiber that consists of conductive PAN (polyacrylonitrile) and PPy (polypyrrole) polymers were used as sensor surfaces. The aptamer modified nanofiber sensor surfaces allowed the determination of the A549 lung cancer cell used as the model case. Disposable pencil graphite electrodes (PGE) were used as a working electrode. Nanofibers were electrospun directly onto PGE surfaces in order to obtain nanofiber modified electrodes (NFPGE) for the first time. The NFPGE electrode was partially hydrolyzed with a NaOH aqueous solution to convert the nitrile groups of the nanofiber into carboxyl groups. Aptamer sequence was immobilized onto functionalized-NFPGE (f-NFPGE) surface covalently via carbodiimide chemistry. The binding of cancer cells onto Aptamer/ f-NFPGE surfaces at 37.5 oC were monitored by Electrochemical Impedance Spectroscopy (EIS) transduction of the Rct in the presence of 5mM [Fe(CN)6]3-/4-. The designed aptasensor's selectivity was performed by using HeLa cells. Optimization of the aptasensor's performance was performed by the detection of optimum probe and target concentrations and washing time conditions. Under the optimized conditions, the selectivity was further investigated by using non-specific aptamer as a recognition molecule and deformed cells as target molecules, respectively. The developed aptansor is related to a low–cost and fast detection methodology in comparison to other cancer monitoring techniques. On the other hand disposable electrode system technique proved applicability of the system to microchip technology. With the detection limit of 3.41 cell /mL shows that the designed aptasensor is capable to perform a highly sensitive detection.