Sensors

Within the Sensors group, we are developing portable, sensitive and selective sensors for the electrochemical detection of persistent and mobile chemicals (PMCs), endocrine disrupting chemicals (EDCs), and biomolecules. The devices consist of sensor elements based on three-terminal screen-printed electrodes (SPEs). connected to a portable IoT potentiostat, enabling inexpensive and user-friendly electrochemical sensors for measurements of real samples.

Figure: Selected analytes within the separate groups chosen for electrochemical detection.

Benzendiols

With the aim of detecting and sensing the presence of Benzenediol isomers in liquid media, our group published an article in Electrochimica Acta titled “Electrochemical detection of benzenediols using carbon-supported catalysts” (https://doi.org/10.1016/j.electacta.2024.144389). To fabricate sensor elements, we modified carbon-based SPEs with 20% Pt or Au nanoparticles, both supported on Vulcan and carbon black, respectively. The nanoparticles were applied as suspensions with Nafion additive for improved binding via dropcasting onto the carbon working electrode. The sensor elements underwent rigorous electrochemical testing using pre-determined concentrations of the three benzenediol isomers mixed with 1 M HCl as the supporting electrolyte. Cyclic Voltammetry (CV) enabled individual identification of each isomer, while Differential Pulse Voltammetry (DPV) allowed simultaneous detection of all isomers in mixed solutions. Chronoamperometry (CA) validated the real-time sensing capability and provided calibration curves for each isomer. The modified SPEs exhibited promising performance, with linear ranges of 1 μM to 3.9 M for catechol (CC), 100 nM to 5 M for resorcinol (RS), and 1 μM to 0.54 M for hydroquinone (HQ). Linear ranges extended up to 100 mM for all isomers, with limits of detection (LoD) and quantification (LoQ) in the micromolar range (LoQ: CC 1 μM; RS 100 nM; HQ 1 μM). These findings underline the high sensitivity and practicality of the sensor elements, confirming that the modification of SPEs provides an economical and effective solution for electrochemical sensing of benzenediol isomers in acidic media.

Figure: Overview of sensing benzenediols in air and/or water using modified SPEs (https://doi.org/10.1016/j.electacta.2024.144389).

Persistent and mobile chemicals

PMCs are the result of the development of modern organic chemistry, and they are found in tens of thousands of everyday products. On the top of the priority list of PMCs are bisphenols. Bisphenol S (BPS) is commonly found in everyday items like thermal paper. It has been identified as easily migrating from paper products onto human skin, subsequently entering the body and disrupting the endocrine system by imitating the estrogen hormone. Given its widespread presence, assessing BPS levels assumes critical significance. In 2024, our group published an article titled “Rapid and reliable electrochemical detection of bisphenol S in thermal paper” in the journal Sensing and Bio-Sensing Research (https://doi.org/10.1016/j.sbsr.2024.100662). The study presents a low-cost, portable electrochemical sensors utilizing SPEs with a carbon (SPE-C) and single-walled carbon nanotube (SPE-SWCNT) working electrode. The sensors were evaluated towards BPS detection using CV, and demonstrated a broad linear range from 1 to 400 µM, with LoDs recorded at 0.73 µM and 0.87 µM for SPE-C and SPE-SWCNT electrodes, respectively, with the latter showing slightly higher sensitivity. Both sensors were also tested for repeatability and were found to perform consistently across 16 measurements using a single electrode. We also showed that both sensors are able to detect BPA and BPS simultaneously, enabling analysis of more complex samples. The SPE-C sensor was also applied to detect BPS extracted from thermal paper samples collected from local shops. The sensor successfully detected BPS in all samples at around 0.9 wt%, and the results were confirmed using ultra-performance liquid chromatography with photodiode-array detection (UPLC-PDA).

Another PMC of great concern is Benzisothiazolinone (BIT), which serves as an antimicrobial agent incorporated into various products, including laundry detergents, water-based paints and food packaging paper, contributing significantly to the contamination of municipal wastewater. Exposure to BIT through skin contact with such products can result in skin sensitization and allergic reactions. Moreover, the discharge or runoff of BIT-containing substances into water bodies poses a substantial threat to aquatic life. Hence, we are developing fast and reliable electrochemical detection methods utilizing carbon and gold-based SPEs. The electrodes demonstrated excellent electrochemical responses for BIT detection. A linear range of 0.25 to 100 µM was obtained with working electrodes based on carbon nanoparticles (SPE-C) and 1 to 100 µM for the working electrodes based on single-wall carbon nanotubes (SPE-SWCNT). CV and square wave voltammetry (SWV) were used to detect BIT in solution, revealing significant differences between the two methods. SWV showed a lower LoD to CV. For instance, with a SPE-C, LoD was was 0.04 µM. The proposed sensor  applied to estimate BIT levels in river samples, indicating its potential suitability for on-site real sample monitoring (Figure s3).

Figure: Electrochemical detection of BIT in river.

Benzotriazole (BZT) is also a notable representative of PMCs, persisting in the environment due to continuous input and low biodegradability. It is widely used as a UV stabilizer in plastics and a corrosion inhibitor for various metals, making it present in food packaging, textiles, plastics, dishwashing detergents, and coolant fluids. Classified as an emerging contaminant, it may be a potential carcinogen and can disrupt the hormonal system with long-term exposure, which is why reliable sensors are essential for detection in the environment. Given its electroactive nature, electrochemical techniques such as voltammetry provide a rapid and efficient means of detection. We are developing a sensor based on a SPE-C, enhanced through modifications of the working electrode. The first modification, incorporating SWCNTs and Nafion, achieved a LoD of 2,4 μM. The second modification, utilizing functionalized Vulcan and sulfonated polyether ether ketone, exhibited a linear detection range of 10–200 μM with an improved LoD of 1,4 μM.

Biomolecules

In the frame of SENSE-PA project we focus on electrochemical detection of biomolecules where we study development of a new sensor platform for the detection of important biological molecules polyamines (PAs), namely putrescine, spermidine, and spermine. They play vital roles in cellular functions, including cell proliferation and division, nucleic acid stabilization, regulation of apoptosis, gene transcription etc.  Their concentration is tightly regulated by homeostasis, and abnormal levels are closely linked to various health conditions, including neurodegenerative diseases and cancer. In particular, elevated PA levels in biological fluids—such as blood, saliva, and urine—have been consistently observed in cancer patients compared to healthy individuals. As such, accurate, point-of-care monitoring of PAs in biological samples is critical for both diagnostic and therapeutic applications.

Since PAs cannot be directly detected due to electrochemical inactivity, most existing PA sensors integrate Prussian blue (PB) with polyamine oxidases. These enzymes catalyse the oxidation of PAs, generating hydrogen peroxide (H₂O₂), which is then detected electrochemically via the PB layer. Known for its exceptional electrocatalytic activity and selectivity for H₂O₂ reduction, PB functions as an artificial peroxidase, enabling H₂O₂ detection at low applied potentials around 0 V vs. Ag/AgCl. However, the stability of the PB layer in biological fluids at neutral pH is limited, reducing its activity and shortening the sensor’s operational lifespan. We are investigating different synthesis approaches for fabricating PB-modified SPEs, focusing on how these methods affect the stability of the PB layer during H₂O₂ sensing in phosphate-buffered saline (PBS). Additionally, we are evaluating the binding performance of several polymers, including polyaniline, polyvinylpyrrolidone, poly(diallyldimethylammonium chloride), and chitosan. Our results demonstrate that incorporating a conductive polymer effectively minimizes material loss while maintaining the sensor’s sensitivity to H₂O₂.

Figure: The intended use of the fabricated portable biosensor based on screen-printed electrodes for PA detection in urine and saliva.