Cell-based impedance spectroscopy (CBI) is a powerful tool that uses the principles of electrochemical impedance spectroscopy (EIS) by measuring changes in electrical impedance relative to a voltage applied to a cell layer. CBI provides a promising platform for the detection of several properties of cells including the adhesion, motility, proliferation, viability and metabolism of a cell culture. This review gives a brief overview of the theory, instrumentation, and detection principles of CBI. The recent applications of the technique are given in detail for research into cancer, neurodegenerative diseases, toxicology as well as its application to 2D and 3D in vitro cell cultures. CBI has been established as a biophysical marker to provide quantitative cellular information, which can readily be adapted for single-cell analysis to complement the existing biomarkers for clinical research on disease progression.

The abnormal levels of four DNA bases, namely guanine (G), adenine (A), thymine (T), and cytosine (C) are implicated in several cancers, metabolic diseases, and HIV/AIDS. Therefore, the accurate detection and concentration measurement of these four DNA bases is of significant interest. Furthermore, there has recently been a push towards developing chemical sensors which are more sustainable and cost-effective. Herein, we developed a graphite paste electrode which incorporated the biochar of sugarcane and methylene blue (GPE-SC-MB) in order to simultaneously detect these four DNA bases. The linear ranges obtained for the four DNA bases are 0.67–38.67 µM for G, 0.67–126.67 µM for A, and 6.67–1600 µM for T and C. The limit-of-detection (LOD) values obtained were 0.037 μM for G, 0.042 µM for A, 4.25 μM for T, and 5.33 µM for C. The electroactive surface area of the electrode as well as the diffusion coefficients for each analyte were determined. Lastly, the GPE-SC-MB was tested in real samples using human saliva with recovery values between 99.0 and 103.0%. Thus, biochar from sugarcane proved to be an effective electrode modifier material for the development of sensitive electrochemical sensors.

In this proof-of-concept study, gold nanoparticles (AuNPs) were immobilized on glassy carbon electrode (GCE) surfaces using a surface-anchored diazonium salt of 4-aminothiophenol (GCE-Ph-S-AuNPs). X-ray photoelectron spectroscopy (XPS) studies confirmed the attachment of the AuNPs via 4-thiophenol onto the surface of the modified electrode. Differential pulse voltammetry (DPV) was performed for the simultaneous determination of guanine (G) and 8-hydroxyguanine (8-OH-G). The calibration curves were linear up to 140 µM and 60 µM with a limit of detection of 0.02 µM and 0.021 µM for G and 8-OH-G, respectively. Moreover, chronoamperometric studies were carried out for the determination of diffusion coefficients of 8-OH-G and G. The GCE-Ph-S-AuNPs were also applied in genomic DNA-spiked samples for the determination of G and 8-OH-G with recovery rates between 98.5% and 103.3%. The novel electrochemical surface provided a potential platform for the sensitive detection of 8-OH-G related to oxidative stress-induced DNA damage in clinical studies.

In this proof-of-concept study, a novel hybrid nanomaterial-based electrochemical sensor was developed for the simultaneous detection of four DNA bases. For the modification of the working electrode surface, graphene oxide quantum dots (GOQDs) were synthesized using a solvothermal method. GOQDs were then used for the preparation of a hybrid nanomaterial with multi-walled carbon nanotubes (GOQD-MWCNT) using a solvothermal technique for the first time. Transmission electron microscopy (TEM) was used to characterize the GOQDs-MWCNTs. A glassy carbon electrode (GCE) was modified with the GOQDs-MWCNTs using Nafion™ to prepare a GOQD-MWCNT/GCE for the simultaneous determination of four DNA bases in phosphate buffer solution (PBS, pH 7.0) using differential pulse voltammetry (DPV). The calibration plots were linear up to 50, 50, 500, and 500 µM with a limit of detection at 0.44, 0.2, 1.6, and 5.6 µM for guanine (G), adenine (A), thymine (T) and cytosine (C), respectively. The hybrid-modified sensor was used for the determination of G, A, T, and C spiked in the artificial saliva samples with the recovery values ranging from 95.9 to 106.8%. This novel hybrid-modified electrochemical sensor provides a promising platform for the future development of a device for cost-effective and efficient simultaneous detection of DNA bases in real biological and environmental samples.

Herein, a novel hybrid bilayer membrane is introduced as a platform to study the aggregation of amyloid-β_1–42 (Aβ_1–42) peptide on surfaces. The first layer was covalently attached to a glassy carbon electrode (GCE) via diazonium electrodeposition, which provided a highly stable template for the hybrid bilayer formation. To prepare the long-chain hybrid bilayer membrane (lcHBLM)-modified electrodes, GCE surfaces were modified with 4-dodecylbenzenediazonium (DDAN) followed by the modification with dihexadecyl phosphate (DHP) as the second layer. For the preparation of short-chain hybrid bilayer membrane (scHBLM)-modified electrodes, GCE surfaces were modified with 4-ethyldiazonium (EDAN) as the first layer and bis(2-ethylhexyl) phosphate (BEHP) was utilized as the second layer. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to characterize the bilayer formation. Both positively charged [Ru(NH₃)₆]³⁺ and negatively charged ([Fe(CN)₆]^3-/4-) redox probes were used for electrochemical characterization of the modified surfaces using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS results showed a decrease in charge transfer resistance (R_ct) upon incubation of Aβ_1–42 on the hybrid bilayer-modified surfaces. This framework provides a promising electrochemical platform for designing hybrid bilayers with various physicochemical properties to study the interaction of membrane-bound receptors and biomolecules on surfaces.

Background: Biomimetic membrane systems can be deposited onto conductive metal surfaces to study the physical properties of membranes as well as the behaviour of proteins within these membranes using electrochemical and surface analytical techniques [1]. Although there are several types of biomimetic membrane, hybrid bilayer lipid membranes (HBLMs) have attracted wide interest. Traditionally, HBLMs have been developed by electrodepositing alkanethiol self‐assembled monolayers onto gold surfaces, which can then be further modified by depositing a secondary phospholipid layer to form the HBLM. Although HBLMs have been widely regarded due to them being robust, relatively straightforward to make, as well as being easy to modify according to the users needs, several concerns surround HBLMs including their reduced fluidity compared to true cell membranes. This is due to the alkanethiol layer being crystalline in nature and more densely packed, resulting in difficulty to reconstitute transmembrane proteins within them.Method: Screen‐printed carbon electrodes are modified with diazonium based phenyl alkyl groups using different protocols to evaluate the biomimetic differences of these novel HBLMs. 2,2‐diphenyl‐1‐picrylhydrazyl is used to prevent the formation of polyaryl layers on the surface of the electrode, hence limiting the electrodeposition to a monolayer. The HBLMs are formed by depositing the second layer in the form of dihexadecyl phosphate, which are analyzed using differential pulse voltammetry, ellipsometry, and X‐ray photoelectron spectroscopy.Result: The different HBLMs presented are embedded with amyloid‐β_1‐42 (Aβ₄₂), the hallmark protein implicated in Alzheimer’s Disease, to assess the protein‐membrane interactions using HBLMs. Aβ₄₂ is known to aggregate to form dimers, oligomers, fibrils, and plaques. Hence using electrochemical techniques, we are able to monitor the aggregation of Aβ₄₂ in the HBLMs. The aggregation process was accelerated by the presence of the bilayer membrane.Conclusion: The electrochemical platform presented here enables us to understand how the interaction of amyloid‐β with the bilayer membrane can alter the aggregation pathways and also affect the formation of toxic oligomer species.References: [1] Fini, H., Hassan, Q., Noroozifar, M. & Kerman, K. Electrografting a Hybrid Bilayer Membrane via Diazonium Chemistry for Electrochemical Impedance Spectroscopy of Amyloid‐β Aggregation. Micromachines 13, 574 (2022).