Electrochemical biosensor

Electrochemical sensing is a common detection method that measures the electron transfer associated with the oxidation/reduction rate in chemical reactions that occur on electrode surfaces. The electrochemical biosensor platforms hold promising applications in the early-stage detection and diagnosis of diseases as robust and adaptable diagnostic and therapeutic systems.

Electrochemical biosensor that functionalizes a reduced graphene oxide (rGO)-based conductive 3D matrix structure on the sensor surface

The integration of novel functional nanomaterials and analytical technologies represents a significant opportunity for advancing electrochemical sensor and biosensor platforms across a wide range of biomedical applications. By employing new surface modifications, microfabrication techniques, and diverse nanomaterials with unique properties, the design of sensitive and selective electrochemical biological sensor platforms becomes achievable. These platforms offer the potential for in vivo and in vitro medical analysis through a well-planned electrode/solution interface. The advantageous attributes of low-cost, miniaturization, easy fabrication, and simultaneous sensing capability are driving the continued growth of electrochemical biosensing platforms. These platforms have captured the attention of interdisciplinary research fields, including chemistry, material science, biological science, and the medical industry.

Antifouling coating comprising glutaraldehyde crosslinked bovine serum albumin and rGO nanoflake have displayed exceptional 3D porous matrix structure for biomolecule characterization in biofluids. We chose to include rGO in the matrix because it is a commonly used functional material in biosensors due to its unique properties, such as high surface area, excellent biocompatibility, and high conductivity. Meanwhile, due to the inclusion of rGO, the coating was able to maintain over 70% of the conductivity level, which is highly desirable for electrochemical characterizations. To immobilize the BSA/ rGO-TEPA mixture on the sensor surface, glutaraldehyde was used as crosslinking agent to react with the mixture, forming schiff bases between the carbonyl ends of GA and the amine groups of BSA/ rGO-TEPA.

Overview of DMF device with EC sensors and the surface characterizations of rGO functioanlization EC electrode

Equivalent Circuit and Modeling of IDEs in electrochemical impedance spectroscopy for cell-assay detection

Electrochemical impedance spectroscopy (EIS) is a powerful analytical technique used to study the electrical behavior of electrochemical systems. The principle behind EIS lies in the application of an AC (alternating current) signal to the electrochemical cell and analyzing the resulting impedance response. By varying the frequency of the AC signal, EIS can probe different electrochemical processes, such as charge transfer reactions, mass transport, and adsorption/desorption phenomena.

An equivalent circuit, which allows the basic characterization of an electrode-electrolyte system, is commonly built to analyze the electrical behavior of the EIS sensor. The experimental components were approximated as ideal electronic components such as capacitors and resistors, in order to correlate the overall impedance and change of the system with each component separately, thus finding optimal measurement parameters for the immunoassay. The EIS was conducted by measuring the impedance response of IDE in DI water, and the resulting impedance and phase were plotted as a function of frequency from 100 Hz to 1 MHz, as shown in Figure a. Bode plot was used here for EIS graphical presentation since it associates the applied frequencies with the electronic components of the electrode systems that are non-faradaic and can reflect key information on detection sensitivity. The simplified equivalent circuit of the non-faradaic regime (no redox probe) was typically presented in Figure 3b, containing two parallel branches (Figure 3c) to present the electrode-electrolyte interface and aqueous media. 𝐶𝑑𝑙 represents the double-layer capacitance formed at the interface of the electrode-electrolyte is due to the accumulated electrical double layer (EDL) under the applied voltage. The aqueous media has both resistive and capacitive responses, and it is presented as solution resistance 𝑅𝑠𝑜𝑙 and solution dielectric capacitance (𝐶𝑑𝑒) connected in parallel.

Impedance magnitude of IDEs in DI water (non-faradaic regime) and the equivalent circuit