Vincenzo Mazzaracchio

The increasing demand for decentralized, accessible, and rapid analytical tools is driving a transformation in healthcare toward point-of-care (POC) analytical technologies. The final aim is to reduce the cost of healthcare management originating from frequent patient hospitalizations and expensive and time-consuming laboratory-based analyses. This review explores the integration of microfluidic technologies with electrochemical sensing platforms, aiming to address the urgent need for POC analytical platforms. Owing to the miniaturization of fluid management systems and exploiting fluid automation, microfluidic devices enable low sample consumption, cost-effective analysis, and multiplexed detection, offering promising tools for real-time health monitoring. Among the other materials, the most commonly used substrates for microfluidics fabrication are paper, PDMS, and adhesive tape, which support custom-designed microchannel architectures, passive fluid motion, and wearable integration. Special attention is given to wearable sensors for sweat analysis, with various approaches employing capillary-driven flows and smart microfluidic designs to enable continuous and autonomous monitoring of biomarkers. Highlighting relevant works from the last 5 years, the review explores the role of integrated microfluidic electrochemical sensing devices in delivering advanced decentralized analytical platforms, with significant potential for clinical use in biomarker detection. Graphical abstract

Printed potentiometric sensors require reliable solid contacts to provide stable and reproducible ion-selective electrodes. However, hampering fabrications and unfavorable maintenance often hinder their breakthrough on a commercial scale. Herein, we develop a solid-contact calcium-selective screen-printed electrode harnessing straightforward manufacturing based on the combination of carbon black (CB) and poly(3,4-ethylene dioxythiophene) doped with poly(sodium 4-styrenesulfonate) (PEDOT:PSS) as an ion-to-electron transducer. Drop-casting was used to simply deposit the CB layer, while PEDOT:PSS was rapidly electropolymerized (71 s) onto the working electrode to deliver affordable manufacturing of the printed electrode while ensuring valid potentiometric performance. Subsequently, the ion-selective membrane (ISM) and the polyvinyl butyral (PVB)-based reference membrane were, respectively, drop-cast onto the working electrode and reference electrode (RE). Upon the optimization of solid-contact layers, the solid-contact Ca²⁺-ISEs were investigated by evaluating their potentiometric performance versus a conventional RE. CB/PEDOT:PSS-modified screen-printed electrodes demonstrated a low-frequency capacitance of 55 μF, and an outstanding standard potential interelectrode reproducibility (±1 mV). The combination of both types of ion-to-electron transducers provided calcium detection in the linear range 10^-1-10^-7 M with a Nernstian sensitivity (28.3 ± 0.3 mV/decade), ensured over 28 days under dry storage. Furthermore, the absence of the water layer effect was also demonstrated. Lastly, the fully printed platform was assembled to achieve a miniaturized and easily field-deployable potentiometric device, consisting of CB/PEDOT:PSS/ISM configuration and PVB-based reference membrane on the working electrode and the RE, respectively. The resulted all-solid-state sensor revealed a Nernstian sensitivity with a 29.0 ± 0.5 mV/decade slope and a stable signal up to 72 h (drift = -0.2 mV/h). Analysis carried out using commercially available bottled water also demonstrated the sensor successful performance in the determination of calcium ion in real samples.

The frequent and excessive use of organophosphorus pesticides in the agriculture industry raises persistent concerns regarding their environmental protection and public health implications. Addressing these issues requires the development of affordable and reliable sensing platforms for on-field monitoring to mitigate their adverse impacts promptly. This study utilizes nanocellulose papers (bacterial and TEMPO-oxidized) combined with butyrylcholinesterase to create a novel reagent-free and orthogonal nanobioplatform featuring smart opto-electrochemical dual outputs. An integrated nano-PAD, preloaded with enzymes and enzymatic substrates, is fabricated using wax-printing and screen-printing technologies. The nano-PAD measures opto-electroactive products, specifically indoxyl and thiocholine, whose concentrations correlate directly with the enzymatic inhibition caused by paraoxon, used as the organophosphate model. To enhance user convenience and meet the requirements for smart real-time point-of-need detection, integration of the nano-PAD with a smartphone-operated miniaturized potentiostat and a self-developed portable smart optical reader is achieved. The developed bioanalytical platform, further supported by a self-developed Android application, enables accurate and efficient quantification of dual signals in real time. The system covers a wide detection range of paraoxon (20-100 ppb) and demonstrates reliable recovery levels (ranging from 98 to 107%) in a real matrix, specifically wastewater. Given these demonstrated capabilities, this innovative biosensing strategy holds substantial potential for practical application in environmental surveillance, facilitating timely and informed environmental management decisions, particularly in resource-limited settings where traditional analytical tools are inaccessible.

Points-of-care (PoCs) augment healthcare systems by performing care whenever needed and are becoming increasingly crucial for the well-being of the worldwide population. Personalized medicine, chronic illness management, and cost reduction can be achieved thanks to the widespread adoption of PoCs. Significant incentives for PoCs deployment are nowadays given by wearable devices and, in particular, by RFID (RadioFrequency IDentification) and NFC (Near Field Communications), which are rising among the technological cornerstones of the healthcare internet of things (H-IoT). To fully exploit recent technological advancements, this paper proposes a system architecture for RFID-and NFC-based PoCs. The architecture comprises in a unitary framework both interfaces to benefit from their complementary features, and gathered data are shared with medical experts through secure and user-friendly interfaces that implement the Fast Health Interoperability Resource (FHIR) emerging healthcare standard. The selection of the optimal UHF and NFC components is discussed concerning the employable sensing techniques. The secure transmission of sensitive medical data is addressed by developing a user-friendly "PoC App" that is the first web app exploiting attribute-based encryption (ABE). An application example of the system for monitoring the pH and cortisol levels in sweat is implemented and preliminarily tested by a healthy volunteer.

The rapid transmission and resilience of coronavirus disease 2019 (COVID‐19) have led to urgent demands in monitoring humoral response for effective vaccine development, thus a multiplex co‐detection platform to discriminate infection‐induced from vaccine‐induced antibodies is needed. Here a duplex electrochemical immunosensor for co‐detection of anti‐nucleocapsid IgG (N‐IgG) and anti‐spike IgG (S‐IgG) is developed by using a two‐working electrode system, via an indirect immunoassay, with antibody quantification obtained by differential pulse voltammetry. The screen‐printed electrodes (SPEs) are modified by carbon black and electrodeposited gold nanoflowers for maximized surface areas, enabling the construction of an immunological chain for S‐IgG and N‐IgG electrochemical detection with enhanced performance. Using an optimized immunoassay protocol, a wide linear range between 30–750 and 20–1000 ng mL⁻¹, and a limit of detection of 28 and 15 ng mL⁻¹ are achieved to detect N‐IgG and S‐IgG simultaneously in serum samples. This duplex immunosensor is then integrated in a microfluidic device to obtain significantly reduced detection time (≤ 7 min) while maintaining its analytical performance. The duplex microfluidic immunosensor can be easily expanded into multiplex format to achieve high throughput screening for the sero‐surveillance of COVID‐19 and other infectious diseases.

The fast-growing healthcare demand for user-friendly and affordable analytical tools is driving the efforts to develop reliable platforms for the customization of therapy based on individual health conditions. In this overall scenario, we developed a paper-based electrochemical sensor for the quantification of iron ions in serum as a cost-effective sensing tool for the correct supplement administration. In detail, the working electrode of the screen-printed device has been modified with a nanocomposite constituted of carbon black and gold nanoparticles with a drop-casting procedure. Square wave voltammetry has been adopted as an electrochemical technique. This sensor was further modified with Nafion for iron quantification in serum after sample treatment with trifluoroacetic acid. Under optimized conditions, iron ions have been detected with a LOD down to 0.05 mg/L and a linearity up to 10 mg/L in standard solution. The obtained results have been compared with reference methods namely commercial colorimetric assay and atomic absorption spectroscopy, obtaining a good correlation within the experimental errors. These results demonstrated the suitability of the developed paper-based sensor for future applications in precision medicine of iron-deficiency diseases. Graphical Abstract