Stainless Steel Foil-Based Label-Free Modular Thin-Film Electrochemical Detector for Solvent Identification.

Most organic solvents are colorless liquids, usually stored in sealed containers. In many cases, their identification depends on the appropriate description on the container to prevent mishandling or mixing with other materials. Although modern laboratories rely heavily on identification technologies, such as digitized inventories and spectroscopic methods (e.g., NMR or FTIR), there may be situations where these cannot be used due to technical failure, lack of equipment, or time. An example of a portable and cost-effective solution to this problem is an electrochemical sensor. However, these are often limited to electrochemical impedance spectroscopy (EIS) or voltammetry methods. To address this problem, we present a novel modular electrochemical sensor for solvent identification that can be used with either an EIS-enabled potentiostat/galvanostat or a simple multimeter. A novel method of fabricating and using a sensor consisting of a thin-film coating of an organic substance on a stainless-steel electrode substrate is presented. The differences in the solubility of the thin film in different solvents are used to distinguish between common organic solvents such as water, ethanol, and tetrahydrofuran.

Electrochromic Device Demonstrator from Household Materials.

Electrochromism encompasses reversible changes of material's optical properties (color, opacity) under the influence of an external electric current or applied voltage. The effect has been known for decades, but its importance continues to grow due to the rapid development of smart systems and the accompanying demand to build devices that consume less power. Most commercial electrochromic devices (ECDs) require sophisticated chemicals and advanced material preparation techniques. Also, the demonstration of electrochromism in chemistry classes mainly uses expensive WO3 films, intrinsically conductive polymers, and/or optically transparent electrodes (OTEs). The aim of this article is to present a simple and fast educational method to build ECDs from household materials without the need for OTEs: unsharpened kitchen knives are used as electrodes, curcumin from turmeric is used as the electrochromic dye, and baking soda is used as the electrolyte. The laboratory experiments presented will help students gain a deeper understanding of the fundamentals of electrochemistry (electrolysis, pH change) and electrochromism (in our case, color changes due to pH-induced keto-enol tautomerism of curcumin).

A549 Cell-Covered Electrodes as a Sensing Element for Detection of Effects of Zn2+ Ions in a Solution.

Electrochemical-based biosensors have the potential to be a fast, label-free, simple approach to detecting the effects of cytotoxic substances in liquid media. In the work presented here, a cell-based electrochemical biosensor was developed and evaluated to detect the cytotoxic effects of Zn2+ ions in a solution as a reference test chemical. A549 cells were attached to the surface of stainless-steel electrodes. After treatment with ZnCl2, the morphological changes of the cells and, ultimately, their death and detachment from the electrode surface as cytotoxic effects were detected through changes in the electrical signal. Electrochemical cell-based impedance spectroscopy (ECIS) measurements were conducted with cytotoxicity tests and microscopic observation to investigate the behavior of the A549 cells. As expected, the Zn2+ ions caused changes in cell confluency and spreading, which were checked by light microscopy, while the cell morphology and attachment pattern were explored by scanning electron microscopy (SEM). The ECIS measurements confirmed the ability of the biosensor to detect the effects of Zn2+ ions on A549 cells attached to the low-cost stainless-steel surfaces and its potential for use as an inexpensive detector for a broad range of chemicals and nanomaterials in their cytotoxic concentrations.

A HepG2 Cell-Based Biosensor That Uses Stainless Steel Electrodes for Hepatotoxin Detection.

Humans are frequently exposed to environmental hepatotoxins, which can lead to liver failure. Biosensors may be the best candidate for the detection of hepatotoxins because of their high sensitivity and specificity, convenience, time-saving, low cost, and extremely low detection limit. To investigate suitability of HepG2 cells for biosensor use, different methods of adhesion on stainless steel surfaces were investigated, with three groups of experiments performed in vitro. Cytotoxicity assays, which include the resazurin assay, the neutral red assay (NR), and the Coomassie Brilliant Blue (CBB) assay, were used to determine the viability of HepG2 cells exposed to various concentrations of aflatoxin B1 (AFB1) and isoniazid (INH) in parallel. The viability of the HepG2 cells on the stainless steel surface was quantitatively and qualitatively examined with different microscopy techniques. A simple cell-based electrochemical biosensor was developed by evaluating the viability of the HepG2 cells on the stainless steel surface when exposed to various concentrations of AFB1 and INH by using electrochemical impedance spectroscopy (EIS). The results showed that HepG2 cells can adhere to the metal surface and could be used as part of the biosensor to determine simple hepatotoxic samples.

Model Electrochemical Biosensor for the Detection of Methanol in Aqueous Solutions with Yeast Cells.

An electrochemical device that serves as a model biosensor and contains yeast Saccharomyces cerevisiae as the active biological element was developed. Different configurations of the electrochemical cells were assembled and tested. Stainless steel was used in the electrochemical cell composition process and the surface of this metal electrode was modified with a thin layer of WO3 if necessary. The yeast Saccharomyces cerevisiae was adhered to the working electrode. The resulting model biosensor was then used to monitor the response to a 10% CH3OH. For detection of biological activity, the electrochemical impedance spectroscopy (EIS) method was applied with a portable potentiostat/galvanostat, where the Bode and the Nyquist plots were interpreted. The stability of the device was beforehand determined by measuring the open circuit potential (OCP). The topography of the electrodes was inspected using the techniques of scanning electron microscopy and optical microscopy. The investigated model biosensor serves as a case study for the development of more complex biosensors that utilize living cells as the active layer.