Miners face severe risks due to toxic gases such as methane (CH₄), carbon monoxide (CO), and hydrogen sulfide (H₂S), which can cause suffocation, poisoning, and fatal accidents. This abstract proposes an IoT-based toxic gas sensor system designed for coal mining environments, providing real-time monitoring, early detection, and automated alerts to enhance miner safety. The system integrates Metal-Oxide Sensors (MOSs), Electrochemical Sensors, and Infrared Sensors (IR) for high-accuracy gas detection. MOSs detect H₂S and CH₄ by measuring electrical conductivity changes when gas molecules interact with a heated semiconductor. Electrochemical sensors measure gas concentration changes by generating an electric current proportional to CO levels, ensuring precise detection. IR sensors identify CO₂ by analyzing infrared absorption at specific wavelengths, enabling non-invasive and selective monitoring. This multi-sensor system achieves high analytical performance, detecting gases at parts per million (ppm) levels. The detection range is 0–500 ppm for CO and up to 5000 ppm for CH₄, with a limit of detection (LOD) of 1–5 ppm, ensuring early warning before dangerous concentrations are reached. The sensors offer high sensitivity, detecting concentration variations as low as 0.1 ppm, and strong selectivity, differentiating gases based on their chemical properties. With a response time of seconds and an error margin of less than ±2%, the system ensures accurate real-time data and rapid intervention during gas leaks. To further improve safety, Artificial Intelligence (AI) models, including ARIMA and Recurrent Neural Networks (RNNs), estimate occupancy levels and CO₂ accumulation, optimizing ventilation through the Key Performance Indicator for Ventilation (KPIv). This AI-driven airflow management system dynamically adjusts ventilation to reduce toxic gas buildup, improve air quality, and enhance mine-wide operational efficiency. By providing continuous monitoring, instant alerts, and intelligent ventilation control, this IoT-based gas detection system significantly mitigates exposure risks, ensuring a safer working environment for miners.

The detection and selective sensing of toxic chemical residues is critical for ensuring food safety and environmental health. We present a MEMS-based microcantilever sensor integrated with a coplanar waveguide (CPW) ring resonator for high sensitivity and selective analyte detection. The sensor facilitates real-time quantitative analysis by employing a label-free as well as single-step selective immobilization method, demonstrating its applicability to various analytes.

The presented CPW ring resonator-integrated MEMS-based microcantilever sensor was modelled and rigorously simulated using a numerical method based on the Finite Element Method (FEM). An operating frequency range of 30–60 GHz was considered in our numerical study. The microcantilever operating in the stress mode was functionalized with a profenofos-specific aptamer (SS2-55), which in turn enabled selective binding to the analyte profenofos, an organophosphorus insecticide. Molecular binding induces surface stress, causing cantilever deflection and a corresponding frequency shift in the S₁₁ parameter.

Significant shifts in the S₁₁ parameter were observed due to different actuation states induced by analyte binding. In its neutral state, the sensor initially exhibited two distinct S₁₁ dips: the primary dip at 53.96 GHz and the secondary dip at 47.48 GHz. Upon complete actuation of the microcantilever, the two dips are merged into a single S₁₁ dip at 50.4 GHz. The presented approach envisages a simpler fabrication protocol and robust system, while the optical methods normally demand sophisticated fabrication and analytical tools. Given these advantages, the detection limit of the presented sensor is 8.24 ng/ml(22.09 nM).

Our rigorous numerically studied CPW ring resonator MEMS sensing device enables the realization of a portable, robust, and precise sensor platform for detecting hazardous residues. The sensor’s adaptability to a broad spectrum of analytes based on an immobilized material makes it a versatile biosensing solution and can be tailored to the label-free detection of various analytes, including bioanalytes for point-of-care biomedical diagnostic and therapeutic devices.

The antibiotic penicillin G (PEN) is commonly used for the treatment of microbial diseases. However, its extensive application in veterinary medicine can cause infiltration into food, especially milk and meat. Therefore, there is an urgent need for rapid and sensitive methods for antibiotic detection. In this study, we used DNA aptamers specific to PEN for its detection using a combined approach based on an acoustic method, quartz crystal microbalance with dissipation (QCM-D), and an optical method, localized surface plasmon resonance (LSPR). QCM-D measures changes in the resonant frequency, Δf, and dissipation, ΔD, while LSPR monitors the shifts in the wavelength corresponding to changes at the surface of gold nanoparticles (AuNPs). Thiolated aptamers were chemisorbed onto the surface of AuNPs with a diameter of 80 nm. Upon the presence of PEN, a shift to a longer wavelength and a decrease in resonant frequency was observed, accompanied by an increase in dissipation due to surface viscosity effects. Significant changes in the acoustic and optical signals were observed down to a PEN concentration of 1 nM, which is lower than the maximum residue limit (MRL) for this antibiotic established by the EU (4 µg/kg, ~ 12 nM). The sensor selectively detects PEN, as demonstrated in experiments with a non-specific antibiotic, oxytetracycline.

Introduction

Monitoring multiple physiological parameters using biosensors is highly valuable for tracking personal wellness, the healthcare of patients, and the physiology of athletes during exercise. However, the primary challenge in terms of technical development remains keeping the technology's price affordable while ensuring effective monitoring of two or more physiological parameters (temperature, blood pressure, etc.) (1) and biomolecules (glucose, lactate, cortisol, etc.) (2).

Methods

In this regard, biosensor channel multiplexing presents an ideal solution allowing us to switch between detection channels to simultaneously measure and monitor multiple physiological parameters and biomolecules. This technology is particularly suitable for potentiometric biosensors where no current is applied after each switch, thereby minimizing noise and capacitive behavior associated with amperometric techniques.

Results

As shown, biosensor channel multiplexing provides fast response time, versatility, and non-destructive measurement. It consumes little energy, making it ideal for battery-powered application. It can be easily integrated and connected to smart devices (smartphones, tables, etc.), enabling the simultaneous detection of multiple parameters or biomolecules.

Conclusions

Multiplexing techniques are important in biosensing for better health tracker monitoring. At Electrochemistry Consulting and Services, we are committed to supporting our clients at every step of the way, starting from strategic consulting services and feasibility studies, through to the troubleshooting and diagnostics of technical issues. We also assist in the design, development, and testing of electrochemical systems and devices.

References

1. Yammine P, El-Nakat H, Kassab R, Mansour A, El Khoury B, Koumeir D, et al. Recent Advances in Applied Electrochemistry: A Review. Chemistry (Easton). 2024 May 23;6(3):407–34.
2. Obeid PJ, Yammine P, El‐Nakat H, Kassab R, Tannous T, Nasr Z, et al. Organ‐On‐A‐Chip Devices: Technology Progress and Challenges. ChemBioChem. 2024 Dec 2;25(23).

Blood glucose level was developed and tested. The test meter was developed for non-invasively monitoring the blood glucose level. This is due to the fact that some forms of monitoring glucose and cholesterol with instruments involve invasive blood tests, which are needless given present-day biomedical instrumentation technology. Given the global prevalence of high blood glucose levels and related issues, there is an urgent need for non-invasive monitoring methods that engage in comfortable testing compared to the traditional blood glucose monitoring method that requires invasive finger-prick tests, which can be painful and discourage consistent use. Addressing this, a non-invasive glucometer was developed using the MAX30100 optical sensor, which measures glucose levels by analyzing light absorption in the skin, utilizing photoplethysmography (PPG), engaged in a non-invasive method that utilizes the reflective and refractive properties of Near-Infrared (NIR) light to determine blood glucose levels. This method offers a painless and real-time alternative for glucose monitoring, aiming to improve accessibility and patient comfort. The system integrates a MAX30100, a pulse oximeter that detects heart rate and oxygen saturation through light absorption. For glucose monitoring, we analyzed changes in infrared and red-light absorption, which vary with glucose levels. The sensor was connected to an Arduino microcontroller to process the data. Signal processing algorithms were used to filter and interpret the absorption patterns, and calibration was performed by correlating sensor readings with known glucose concentrations. The meter was used on nine subjects, and error analysis was carried out using Clarke Error Grid Analysis (EGA) and Surveillance Error Grid (SEG) analysis. The findings from both Clarke Error Grid Analysis (EGA) and Surveillance Error Grid (SEG) analysis suggest that, while the device is generally reliable, there is room for improvement.

Bloodstream infections (BSIs) are a major cause of life-threatening complications in patients with cancer. According to the statistical data, the prevalence of BSIs ranges from 11% to 38%, and overall mortality reaches about 40%. Immediate antibiotic treatment could greatly shorten hospital stays, decrease the mortality rate and decrease healthcare costs. Therefore, a fast detection of bacteria for BSI determination is in high demand. Here, a novel paper-based microfluidic chip with water-absorbing material for generating sample fluid flow is designed for the detection of bacteria in whole blood. The corresponding green quantum dots for the labelling of target S. aureus are prepared by modifying their surfaces with an aptamer for specific binding. Blood cells are separated during diluted sample solution flow in the chip to eliminate interferences and the labelled bacteria are captured at the detection area in the chip. Fluorescent intensity is then measured using a microscope to determine the number of target bacteria in whole blood. The assay of S. aureus in whole blood, which is prepared by adding bacteria into the blood sample, shows that this method could detect bacteria in less than 20 min with a detection limit as low as 10 CFU/mL. It is much faster than clinical tests using the culture method, PCR or mass spectroscopy. The developed method does not require the use of large-scale equipment and complex manual operations. This point-of-care-testing (POCT) method is envisioned to be used for the rapid assessment of certain bacterial infection in BSIs.

Paper-based analytical devices (PADs) have gained widespread attention due to their potential as simple, low-cost, and sustainable analytical devices with the main scope of preliminary monitoring. A ready-to-use colorimetric paper-based sensor for nitrite detection in environmental and clinical samples was developed [10.1039/D4SD00308J]. The sensor is based on the colorimetric Griess reaction, a double-step reaction that includes a diazotization of sulfanilamide in acidic conditions, which forms a diazonium salt, and its coupling with N-(1-naphthyl)ethylenediamine to produce a pink azo dye. Paper has been used as support for reagent immobilization and an origami-based mechanism has been chosen to initiate the reaction without requiring additional handling of chemicals. Unlike conventional nitrite assays, which require multiple steps, specialized instrumentation, and qualified personnel, this sensor enables rapid, user-friendly detection through a smartphone camera, with the option for qualitative assessment via the naked eye. The paper-based sensor demonstrated satisfactory analytical performance when used to analyze drinking water, with recovery rates between 87% and 110%, and detection and quantification limits of 0.27 mg L^-1 and 1.11 mg L^-1, respectively. In addition, for nitrate determination, nitrate reductase was implemented prior to the Griess reaction. The system was stable for at least 1 month at +4°C, maintaining 98% of its performance. The selectivity was studied using ions and potential interferents like BSA, urea, or glucose as common compounds present in environmental or clinical matrices. Another important aspect of this system is its sustainability, which has been evaluated through the 12 principles of white analytical chemistry (WAC) using the 12 algorithms [10.1016/j.trac.2021.116223]. Its sustainability and ease of use make it a promising tool for environmental monitoring and point-of-care (POC) applications. The biosensor was used to detect nitrite and nitrate in water and clinical samples such as saliva and exhaled breath condensate to evaluate its potential as an indicator of inflammation or infection.

Disinfection plays a crucial role in the production of potable water, the maintenance of swimming pools, the sanitation of food industry facilities, and medical and hospital environments. Among disinfection methods, chlorination involves the use of gaseous chlorine, chlorine dioxide, calcium hypochlorite, or, most commonly, sodium hypochlorite. It is important to monitor the concentration of free residual chlorine, i.e., the amount of disinfectant remaining in water after treatment. Residual free chlorine can react with natural organic matter to form disinfection by-products classified as carcinogens. The ISO 7393-2 standard detects free residual chlorine by its reaction with N,N-diethyl-p-phenylenediamine (DPD), producing a pink complex with intensity proportional to the residual chlorine concentration. The method requires benchtop instrumentation and trained personnel, making routine monitoring expensive and time-consuming. A paper-based colorimetric sensor was developed as a low-cost, rapid, portable, and user-friendly alternative. The sensor leverages color change resulting from the DPD reaction and allows naked-eye detection. Quantitative analysis can be performed in only 3 min by capturing images of the sensor using a smartphone, allowing for precise colorimetric evaluation. This approach achieved a detection limit of 12 μM for sodium hypochlorite, making it a promising tool for routine water quality monitoring applications.

Hydrogen sulfide (H₂S) is the most recently identified endogenous gasotransmitter, along with molecules such as nitric oxide (NO) and carbon monoxide (CO). It has been recognized as a key mediator in various physiological processes, such as cellular homeostasis, as well as in pathological conditions, including cancer. Specifically, H₂S exerts different effects on cancer cells depending on its concentration and exposure time. At lower concentrations, it can promote tumor cell growth and proliferation, whereas higher concentrations may inhibit growth or induce apoptosis. Due to its biphasic behavior, H₂S is a promising biomarker for both diagnostic and therapeutic strategies in cancer, with potential applications in liquid biopsy for non-invasive early detection of tumor progression and treatment response. Given the challenging nature of H₂S detection, there is a growing need for sensitive analytical techniques, such as electrochemical methods, to accurately measure its levels. Considering this, a novel paper-based electrochemical sensor was fabricated for the detection of this gas trasmitter in H₂S-exposed murine tissue lysates, with possible applications in liquid biopsy. The sensor, screen-printed on filter paper, was modified with a Prussian blue (PB) dispersion, synthesized directly on the paper support. Analytical characterization was performed in standard solutions, achieving a detection limit of 3 μM with an adequate repeatability, under 10%. This electroanalytical method was then applied for the detection of H₂S levels in murine skin lysate, untreated cancer murine lysates, and pharmacologically-treated neoplastic murine lysate, validating the accuracy and reliability of the technique. It indicates a notable improvement in portable point-of-care (POC) platforms for cancer diagnostics, allowing rapid, on-site testing with minimal sample volume requirements, simplified procedures, and timely, minimally invasive cancer detection. The use of miniaturized, portable sensors, in particular, allows for a reduction in sample size, which usually presents an issue in traditional approaches.

Food fraud remains an issue with significant environmental, health, and socio-economic impacts for consumers and the food industry alike. Honey, known for its natural sweetness, rich nutritional value, and numerous health benefits, is among the most adulterated foods found in the global market. Common fraudulent practices include mislabelling the honey’s botanical origin, blending it with lower-quality honeys, processed sugars, or other substances. Moreover, as most of their beneficial properties are linked to honey’s botanical origin, it is important to assure the safety and quality of the honey. Nonetheless, with the increasing number of reports on tampered or adulterated products appearing, there is a pressing need to develop an analytical tool that can quickly, affordably, and reliably ensure the quality and safety of honeys. In this study, an innovative inkjet-printed gold electrode paper-based biosensing platform coupled with gold-coated magnetic nanoparticles (MNPs) was developed to detect the genomic DNA of two plant species from which honey can be produced: Castanea sativa and Erica arborea. Analyzing public database platforms, a DNA-target probe for both C. sativa and E. arborea were selected and designed. These sensors resulted from the DNA hybridization reaction between the two complementary probes specific to both plant species in a sandwich format. Their complementary probes were modified with an amine (NH₂) group and a fluorescein isothiocyanate and cut in two to generate the enzymatic amplification of the electrochemical signal. The hybridization reaction was labeled with enzymes, enabling chronoamperometric measurement of peroxidase activity associated with the MNPs on the gold electrode surface. The developed biosensor was then successfully applied to detect C. sativa and E. arborea present in real plant samples and, hence, determine the botanic origin of the honeys. Therefore, these MNPs and paper-based biosensors are a viable and rapid tool to help authenticate the origin of honeys.