Ultrasensitive Electrochemical Impedance Detection of Mycoplasma agalactiae DNA by Low-Cost and Disposable Au-Decorated NiO Nanowall Electrodes

Abstract

Nanostructured electrodes detecting bacteria or viruses through DNA hybridization represent a promising method, which may be useful in on-field applications where PCR-based methods are very expensive, time-consuming, and require trained personnel. Indeed, electrochemical sensors combine disposability, fast response, high sensitivity, and portability. Here, a low-cost and high-surface-area electrode, based on Au-decorated NiO nanowalls, demonstrates a highly sensitive PCR-free detection of a real sample of Mycoplasma agalactiae (Ma) DNA. NiO nanowalls, synthesized by aqueous methods, thermal annealing, and Au decoration, by electroless deposition, ensure a high-surface-area platform for successful immobilization of Ma thiolated probe DNA. The morphological, chemical, and electrochemical properties of the electrode were characterized, and a reproducible detection of synthetic Ma DNA was observed and investigated by impedance measurements. Electrochemical impedance spectroscopy (EIS) ascribed the origin of impedance signal to the Ma DNA hybridization with its probe immobilized onto the electrode. The electrode successfully discriminates between DNA extracted from healthy and infected sheep milk, showing the ability to detect Ma DNA in concentrations as low as 53 ± 2 copy number μL −1 . The Au-decorated NiO nanowall electrode represents a promising route toward PCR-free, disposable, rapid, and molecular detection.

Trapping and detecting nanoplastics by MXene-derived oxide microrobots

“…15 ). This mechanism, similar to the one at the base of DNA hybridization sensors, contributed to the R ct increase 62 .…”

“…The fit of the EIS spectrum based on an equivalent circuit model allows the determination of the circuit parameters. By monitoring these parameters, EIS can be used to sensitively detect impedance variations at the electrolyte/electrode interface caused by the adsorption of molecules or particles 62 .…”

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“…The changes to the phase angle were not signicant. 78 Bode phase angle plots provide further information for the characterization of conductive materials, such as supercapacitors 19 and sensors. 14 For example, the capacitor response frequency (f 0 ) is characterized as the position of equal resistive and capacitive impedance, 20 and the relaxation time constant (s 0 ) which is dened as the minimum time for discharging all energy from a device that has an efficiency larger than 50%.…”

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“…As a result, they showed that this type of electrode can detect DNA in the concentration range from 10 fmol/L to 1 nmol/L. Another DNA EIS-sensor was recently proposed in ref 139, where the authors have used an Au-decorated NiO nanowall electrode covered by DNA from Mycoplasma agalactiae. Unlike the previously discussed DNA sensor, this device demonstrates efficiency over a range of relatively high DNA concentrations (0.2−1.5 μmol/L), which nevertheless allows it to be used for fast, accurate, and inexpensive detection of Mycoplasma agalactiae in sheep milk.…”