Multi-Tailoring of a Modified MOF-Derived CuxO Electrochemical Transducer for Enhanced Hydrogen Peroxide Sensing

Reasonable control of the redox states within the catalytic units together with the interconnection degrees of the substrate is of great significance in the modulation of a well-performed transducer. Herein,...

Electrochemical Behavior of Screen-Printed Carbon Electrodes as Transducers in Biosensors

Screen-printed carbon electrode (SPCE) was examined as a transducer substrate for application in electrochemical sensors. Aqueous solutions of 0.1 M KCl and 0.1 M KCl + 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] (redox solution) were prepared to simulate the environment of faradaic and non-faradaic sensing, respectively. The SPCE presented an irregular surface composed by two main carbon phases. Raman spectroscopy results revealed the presence of peaks around 1,580 cm−1 and 1,334 cm−1 related to the G and D bands corresponding to sp2 carbon atoms (graphite flakes) and a multitude of broad bands associable to amorphous sp3 carbon in the ink matrix. Conductive atomic force microscopy indicated that the irregular structure of the SPCE led to the heterogeneous distribution of the current over the surface and the electroactivity of this material was mainly attributed to the presence of graphite. Polarization curves and electrochemical impedance spectroscopy (EIS) revealed that the redox solution was more aggressive to the SPCE, despite this electrode was achieved a quasi-steady state for 1 h under the effect of a polarization potential in both electrolytes, which justifies its use as an electrochemical transducer in faradaic and non-faradaic devices.

TiO2 Sol-gel Coating as a Transducer Substrate for Impedimetric Immunosensors

Given the importance of the transducer elements in the performance of sensors for various applications, as well as the growing search for devices that are capable of providing the response in shorter time, in this work, titanium dioxide was examined as a candidate for application in an electrochemical biosensor. A TiO2 coating deposited by sol-gel method on a silicon wafer was obtained with an anatase crystalline structure, as an n-type<br /> semiconductor with donor density equal to 2.954 · 1017 cm–3. Its surface was functionalized to be tested as a biosensor to detect snake venom of the Bothrops genera, and each step of the functionalization was investigated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic voltammetry. Despite being less sensitive than the reference method ELISA, the TiO2-based biosensor was also capable of detecting the analyte of interest at 20 μg mL–1, revealing an increase in its leakage resistance and phase shift after incubation in this solution. Furthermore, the total time for carrying out the biodetection with the TiO2-coated device (41.24 ± 0.05 min) was estimated to be approximately 80 % shorter than that required by the labelled standard assay, which indicates that TiO2 is a promising electrochemical transducer for biosensing applications.

The Role of Electrochemical Immunosensors in Clinical Analysis

An immunosensor is a kind of affinity biosensor based on interactions between an antigen and specific antigen immobilized on a transducer surface. Immunosensors possess high selectivity and sensitivity due to the specific binding between antibody and corresponding antigen, making them a suitable platform for several applications especially in the medical and bioanalysis fields. Electrochemical immunosensors rely on the measurements of an electrical signal recorded by an electrochemical transducer and can be classed as amperometric, potentiometric, conductometric, or impedimetric depending on the signal type. Among the immunosensors, electrochemical immunosensors have been more perfected due to their simplicity and, especially their ability to be portable, and for in situ or automated detection. This review addresses the potential of immunosensors destined for application in clinical analysis, especially cancer biomarker diagnosis. The emphasis is on the approaches used to fabricate electrochemical immunosensors. A general overview of recent applications of the developed electrochemical immunosensors in the clinical approach is described.