Abstract
In this work, a low-cost and rapid electrochemical resistive DNA biosensor based on the current relaxation method is described. A DNA probe, complementary to the specific human papillomavirus type 16 (HPV-16) sequence, was immobilized onto a screen-printed gold electrode. DNA hybridization was detected by applying a potential step of 30 mV to the system, composed of an external capacitor and the modified electrode DNA/gold, for 750 µs and then relaxed back to the OCP, at which point the voltage and current discharging curves are registered for 25 ms. From the discharging curves, the potential and current relaxation were evaluated, and by using Ohm’s law, the charge transfer resistance through the DNA-modified electrode was calculated. The presence of a complementary sequence was detected by the change in resistance when the ssDNA is transformed in dsDNA due to the hybridization event. The target DNA concentration was detected in the range of 5 to 20 nM. The results showed a good fit to the regression equation , and a detection limit of 2.39 nM was obtained. As the sensing approach uses a direct current, the electronic architecture of the biosensor is simple and allows for the separation of faradic and nonfaradaic contributions. The simple electrochemical resistive biosensor reported here is a good candidate for the point-of-care diagnosis of HPV at a low cost and in a short detection time.
Highlights
The International Agency for Research on Cancer (IARC) estimates that the number of cases of invasive cervical cancer in 2020 was 557,088 with more than 297,122 deaths caused by the disease
In order to compare the Rtotal values obtained from the relaxation curves, electrochemical measurements of the modified electrodes were performed in PBS solution by using the electrochemical impedance spectroscopy (EIS) technique and obtaining the resistance values by a nonlinear least squares fitting (CNLS) of the experimental impedance data
HPV DNA sequence attached to the Au surface and their electrochemical changes, which are related to the hybridization process and associated redox reactions
Summary
The International Agency for Research on Cancer (IARC) estimates that the number of cases of invasive cervical cancer in 2020 was 557,088 with more than 297,122 deaths caused by the disease. By detecting changes that occur during hybridization at the interface between a DNA functionalized electrode and a conductive target analyte solution, electrochemical techniques have the potential to provide real-time measurement, label-free sensing, and more portable detection platforms [25]. A major advantage of EIS is that detection can be performed label free, i.e., the changes in the electrical properties of the electrode surface arise from the interaction with the target molecule alone [28]. Even though this technique is highly sensitive, this advantage sometimes limits its application as a result of being liable to respond to interferences, too. Solutions of complementary and single-base mismatch sequences were used; the hybridization response of each was compared by using a Student’s t-test
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