Electron transfer studies of a conventional redox probe in human sweat and saliva bio-mimicking conditions

Abstract

Modern day hospital treatments aim at developing electrochemical biosensors for early diagnosis of diseases using unconventional human bio-fluids like sweat and saliva by monitoring the electron transfer reactions of target analytes. Such kinds of health care diagnostics primarily avoid the usage of human blood and urine samples. In this context, here we have investigated the electron transfer reaction of a well-known and commonly used redox probe namely, potassium ferro/ferri cyanide by employing artificially simulated bio-mimics of human sweat and saliva as unconventional electrolytes. Typically, electron transfer characteristics of the redox couple, [Fe(CN)6]3−/4− are investigated using electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. Many different kinetic parameters are determined and compared with the conventional system. In addition, such electron transfer reactions have also been studied using a lyotropic liquid crystalline phase comprising of Triton X-100 and water in which the aqueous phase is replaced with either human sweat or saliva bio-mimics. From these studies, we find out the electron transfer reaction of [Fe(CN)6]3−/4− redox couple is completely diffusion controlled on both Au and Pt disc shaped electrodes in presence of sweat and saliva bio-mimic solutions. Moreover, the reaction is partially blocked by the presence of lyotropic liquid crystalline phase consisting of sweat and saliva bio-mimics indicating the predominant charge transfer controlled process for the redox probe. However, the rate constant values associated with the electron transfer reaction are drastically reduced in presence of liquid crystalline phase. These studies are essentially carried out to assess the effect of sweat and saliva on the electrochemistry of Fe2+/3+ redox couple.

PEDOT-AuNPs-based impedimetric immunosensor for the detection of SARS-CoV-2 antibodies

“…The first one, located around -0.5 V / -0,.2 V, is related to PEDOT redox reaction, as detailed by Sterby et al [54] . Another redox process is located at 0.3 V / 0.0 V, that is associated with Fe(CN) 6 4-/3- conversion by electron transfer and its well-defined peak profile suggests that the process occurs by diffusion [53] . A shift towards higher potential values and a decrease in peak current intensity are observed in the voltammograms after AG and BSA immobilization, suggesting an increasing difficulty for the Fe(CN) 6 4-/3− redox reaction to occur at the electrode / electrolyte interface.…”

“…Chemically modified electrodes are commonly investigated using redox probes, such as potassium ferro / ferricyanide ([Fe(CN) 6 ] 3-/4− ), since the electron transfer charge depends on the electrode interface characteristics, mainly its chemical nature [53] . Thus, the modification steps can be observed by the electrochemical measurements performed on [Fe(CN) 6 ] 3-/4- / PBS electrolyte.…”

Correlations of Salivary and Blood Glucose Levels among Six Saliva Collection Methods

“…Thus, saliva may be an excellent substitute for blood. [ 19 ]. Caixeta et al [ 20 ] demonstrated that salivary glucose was a potential outcome for screening, diagnosing, and monitoring DM, as they found a 95.2% accuracy of the laboratory test of salivary glucose in response to blood glucose.…”

Use of PEDOT:PSS/Graphene/Nafion Composite in Biosensors Based on Acetic Acid Bacteria

“…Figure 4 shows Nyquist plots of impedance for the stepwise modification of carbon SPE. The data were obtained by using 5 mM K 3 [Fe(CN) 6 ] as a redox label (the standard redox active marker for EIS [25]). The impedance spectra are illustrated by semicircle-like shapes related to the electron transfer.…”