Nowadays, we are assisting in the exceptional growth in research relating to the development of wearable devices for sweat analysis. Sweat is a biofluid that contains useful health information and allows a non-invasive, continuous and comfortable collection. For this reason, it is an excellent biofluid for the detection of different analytes. In this work, electrochemical sensors based on polyaniline thin films deposited on the flexible substrate polyethylene terephthalate coated with indium tin oxide were studied. Polyaniline thin films were abstained by the potentiostatic deposition technique, applying a potential of +2 V vs. SCE for 90 s. To improve the sensor performance, the electronic substrate was modified with reduced graphene oxide, obtained at a constant potential of −0.8 V vs. SCE for 200 s, and then polyaniline thin films were electrodeposited on top of the as-deposited substrate. All samples were characterized by XRD, SEM, EDS, static contact angle and FT-IR/ATR analysis to correlate the physical-chemical features with the performance of the sensors. The obtained electrodes were tested as pH sensors in the range from 2 to 8, showing good behavior, with a sensitivity of 62.3 mV/pH, very close to a Nernstian response, and a reproducibility of 3.8%. Interference tests, in the presence of competing ions, aimed to verify the selectivity, were also performed. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance.

Chloride ions and uric acid are two key biomarkers that play a crucial role in oxidative stress, a pathological condition that can lead to serious diseases if not monitored and identified on time. In this work, we focus on developing an innovative device based on an electrochemical sensor and a paper microfluidic system for the early detection of these biomarkers in sweat. The electrochemical sensor consists of a silicon chip containing thin-film gold electrodes modified by electrodeposition with silver and a composite of reduced graphene oxide and gold nanoparticles for the detection of chloride ions and uric acid, respectively. An initial performance assessment of the sensors in batch in buffer and artificial sweat solutions was conducted using chronoamperometry. Calibration curves were obtained in both media. Chloride ions were detectable in the range of 1-100 mM with a sensitivity of 1.40 μA mM-1 in buffer, while the range and sensitivity in artificial sweat were 1-100 mM and 1.44 μA mM-1. Uric acid was detectable with a sensitivity of 1.610 μA mM-1 and a linear range of 10-500 μM in buffer. The corresponding values in artificial sweat were 1.583 μA mM-1 and 10-500 μM). These analytical values indicate minimal interference and a very small matrix effect when measurements were conducted in artificial sweat. The sensors were integrated with a paper microfluidic component to assess the effectiveness of the device in monitoring chloride ion and uric acid levels in sweat with a very low sample volume (7 μL) for non-invasive and low-cost evaluation of oxidative stress.

Chronic Obstructive Pulmonary Disease (COPD) is a chronic inflammatory degenerative disease. Disease exacerbations accelerate lung function deterioration. Airway epithelium has a central role in COPD pathophysiology. Airway epithelium releases alarmins including the thymic stromal lymphopoietin (TSLP) in response to exogenous stressors. Notch-1 in the nucleus acts as inhibitor of TSLP gene expression. Here, we investigated, in human bronchial epithelial cells, the effects of cigarette smoke extract (CSE) in TSLP production exploring the relationship with oxidative stress events and with Notch-1 signaling. In CSE exposed 16HBE, the effects of carbocysteine were assessed on: intracellular and extracellular oxidative stress; nuclear Notch-1 expression; TSLP gene expression. The TSLP levels in sera from non-smokers, smokers and exacerbated COPD patients (before and after therapy with carbocysteine) were also explored. CSE induced TSLP gene expression and oxidative stress and reduced nuclear expression of Notch-1 in 16HBE. The use of an electrochemical sensor allowed a reliable tool to assess oxidative stress. TSLP concentrations were higher in sera from smokers and exacerbated COPD than in sera from non-smokers. Carbocysteine was able to counteract the effects of CSE in oxidative stress and in TSLP gene expression in 16HBE and to reduce TSLP in exacerbated COPD. In conclusion, increased oxidative stress induced by smoke exposure in airway epithelium leads to increased TSLP production and carbocysteine in vitro and in vivo mitigates the induced TSLP production. Oxidative stress detection by electrochemical sensors can open new avenues for evaluating epithelial damage and for identifying patients eligible to alarmin targeted biologics.

Quantification of oxidative stress is a challenging task that can help in monitoring chronic inflammatory respiratory airway diseases. Different studies can be found in the literature regarding the development of electrochemical sensors for H₂O₂ in cell culture medium to quantify oxidative stress. However, there are very limited data regarding the impact of the cell culture medium on the electrochemical quantification of H₂O₂. In this work, we studied the effect of different media (RPMI, MEM, DMEM, Ham’s F12 and BEGM/DMEM) on the electrochemical quantification of H₂O₂. The used electrode is based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) and was obtained by co-electrodeposition. To reduce the electrode fouling by the medium, the effect of dilution was investigated using diluted (50% v/v in PBS) and undiluted media. With the same aim, two electrochemical techniques were employed, chronoamperometry (CH) and linear scan voltammetry (LSV). The influence of different interfering species and the effect of the operating temperature of 37 °C were also studied in order to simulate the operation of the sensor in the culture plate. The LSV technique made the sensor adaptable to undiluted media because the test time is short, compared with the CH technique, reducing the electrode fouling. The long-term stability of the sensors was also evaluated by testing different storage conditions. By storing the electrode at 4 °C, the sensor performance was not reduced for up to 21 days. The sensors were validated measuring H₂O₂ released by two different human bronchial epithelial cell lines (A549, 16HBE) and human primary bronchial epithelial cells (PBEC) grown in RPMI, MEM and BEGM/DMEM media. To confirm the results obtained with the sensor, the release of reactive oxygen species was also evaluated with a standard flow cytometry technique. The results obtained with the two techniques were very similar. Thus, the LSV technique permits using the proposed sensor for an effective oxidative stress quantification in different culture media and without dilution.

High concentrations of H₂O₂, indicative of increased oxidative stress in the lung, are observed in the exhaled breath of individuals affected by different respiratory diseases. Therefore, measuring H₂O₂ in exhaled breath represents a promising and non-invasive approach for monitoring the onset and progression of these diseases. Herein, we have developed an innovative, inexpensive, and easy-to-use device for the measurement of H₂O₂ in exhaled breath. The device is based on a silver layer covered with an electrodeposited thin film of chitosan, that ensures the wettability of the sensor in a humid atmosphere. The s-ensor was calibrated in the aerosol phase using both phosphate buffer solution and cell culture medium. In the buffer, a sensitivity of 0.110 ± 0.0042 μA μM⁻¹ cm⁻² (RSD: 4%) and a limit of detection of 30 μM were calculated, while in the cell culture medium, a sensitivity of 0.098 ± 0.0022 μA μM⁻¹ cm⁻² (RSD 2%) and a limit of detection of 40 μM were obtained. High selectivity to different interfering species was also verified. The sensor was further tested versus an aerosol phase obtained by nebulizing the culture medium derived from human bronchial epithelial cells that had been exposed to pro-oxidant and antioxidant treatments. The results were comparable with those obtained using the conventional cytofluorimetric method. Finally, sensor was tested in real exhaled breath samples and even after undergoing physical deformations. Data herein presented support that in future applications this device can be integrated into face masks allowing for easy breath monitoring.

Despite their substantial economic and financial burden, modern healthcare systems are frequently criticized for their poor efficiency and inclusivity, and substantial concerns arise about their capability to provide adequate responses to the population's needs in the near future. In such context, new digital healthcare models based on advanced bio-sensing technologies are regarded as a possible solution to improve the screening and prevention processes thus improving the overall performance of the healthcare supply chains. This is particularly relevant for respiratory diseases, which are currently among the first causes of death and medical expenditures in industrialized countries. In this research, a new approach to the testing and diagnosis of respiratory diseases is proposed as a new e-health model based on a fog-based architecture and a smart device. According to such a model, the fog-based system that allows for patients’ testing through the analysis of the exhaled breath is collected using a smart device based on a novel nanostructured sensor integrated into a breathing mask, and capable of transferring relevant patient information to a centralized decision-making process. The objective of this new healthcare model is thus to improve the diagnosis process of respiratory diseases by minimizing under-diagnosed or late-diagnosed cases. The practical relevance of the approach proposed is the possibility of enabling remote diagnostics of respiratory diseases without the need for skilled medical staff and bulky equipment only available in specialized labs, thus allowing for decentralized patient testing and self-testing. The original testing method and system proposed have been validated in the lab using samples extracted from real patients.