Opportunities and challenges of using ion-selective electrodes in environmental monitoring and wearable sensors

Great opportunities exist for Ion-Selective Electrodes (ISEs) in the fields of environmental monitoring and of wearable applications for example as the sensing part in wireless networks. In this review special attention is given to the recent results obtained with Solid Contact Ion-Selective Electrodes and Solid Contact Reference Electrodes. Their combination as disposable sensing platform may offer the best solution to eliminate issues commonly experienced with ISEs and lead in a short term to their commercialization. Future research will likely focus on the miniaturization of the current devices and on the further development of non conventional potentiometric methods, e.g., controlled potential thin-layer coulometry

Nano- and micro- electrodes: applications in the biosensing field

Platinum and gold inlaid disk micro- and nano-sized electrodes were prepared using a laser puller. It is the very first time that a similar procedure is fully described for the preparation of gold microelectrodes. Scanning Electron Microscopy, Cyclic Voltammetry, High Speed Chronoamperometry and Scanning Electrochemical Microscopy were used to characterize the electrodes. Radius of platinum and gold tips ranged from 7 nm and 500 nm up to several micrometers, respectively. Platinum probes with radius < 200 nm were employed in high resolution SECM imaging of an array of nanocavities (600–700 nm wide and 400-500 nm deep) prepared by means of nanosphere lithography. The small size of the probe employed in the study allowed resolving the features of the sample, showing the significant capability to do electrochemistry with submicrometer spatial resolution. The small size of these electrodes allowed their application as immunosensors using the steady-state current of a redox probe as transducing principle. In fact, an object having larger size than the electrode blocks the diffusing of the redox probe towards the electrochemical active surface. Indeed, platinum UMEs were coated with Goat-Human Immunoglobulin (hIgG) while anti-hIgG labelled polystyrene microspheres were injected into the electrochemical cell and let settle. Stable step like decreases (~ 2- 5 %) in the UME current were interpreted as binding of a single bead on the electrode surface due to the immunological reaction between hIgG and anti-hIgG. When the microelectrodes are uncoated, no immunological reaction can occur and then no stable step-like decrease should be observed. However, it was noticed that the electrostatic attraction between the electrode and the microspheres could cause the stabilization of the beads on the electrode surface and produce similar stable step-like drops in the current. Finally, UMEs were employed in the preparation of glucose microsensors which were based on the glucose oxidase immobilization and in the anodic oxidation of the enzymatically produced hydrogen peroxide. Indeed, a comparative study of the results obtained with four enzyme immobilization procedures was carried out. The work highlighted that the high concentration of glucose oxidase necessary to have sensitive microsensors hampered the polymerization of pyrrole. On the other hand, the microsensors prepared by entrapment of the enzyme in a polyphenol matrix showed good sensitivity (~ 1 - 2 mAM-1cm-2) and very fast response time (< 4 seconds). Direct glucose oxidase deposition induced by applied potential did not improve the performances compared to the latter case. Finally, sensors prepared by ruthenium electrodeposition in presence of the enzyme showed encouraging results in terms of enhanced sensitivity (~ 10 - 20 mAM-1cm-2) However, a drift in the amperometric signal prevents its analytical use at the moment

Distributed environmental monitoring

With increasingly ubiquitous use of web-based technologies in society today, autonomous sensor networks represent the future in large-scale information acquisition for applications ranging from environmental monitoring to in vivo sensing. This chapter presents a range of on-going projects with an emphasis on environmental sensing; relevant literature pertaining to sensor networks is reviewed, validated sensing applications are described and the contribution of high-resolution temporal data to better decision-making is discussed

Disposable potentiometric strips: a versatile tool for low-cost sensing

The integration of sensors within wireless networks represents a pivotal step for remote analytical monitoring, not limited to pollutants in the environment but also suitable for diagnostics and personal health monitoring. For instance, higher spatial and temporal resolutions for toxic metals are fundamental for epidemiology studies, where they would help to establish definitive associations between the exposure to specific chemicals and the health of individuals and communities. In addition, accessible body fluids such as saliva and sweat represent an interesting medium for the realization of wearable sensors. These fluids contain important personalized physiological information. For example, a continuous monitoring of pH in saliva and electrolyte concentrations in sweat would be beneficial for controlling healthy mouth conditions or to improve endurance performances and avoid critical situations, e.g., dehydration and hyponatremia in athletes. Low-cost potentiometric strips based on screen printed substrates consisting of a solid-contact ion-selective electrode (SC-ISE) combined to a solid-contact reference electrode (SC-RE) may offer a versatile tool in sensing technology. These strips can be readily adapted for the detection of several ionic species. Here, as an example, we present on the monitoring of pH in saliva, Na+ in sweat and Pb2+ in water. The strip is plugged into an electronic platform of reduced dimensions which converts the chemical information into an electric signal, wireless transmitted to a base station. This technology may have an impact in remote monitoring but also in wearable sensing thanks to the device miniaturization

A potentiometric disposable sensor strip for measuring pH in saliva

In this paper, the preparation of a potentiometric strip for pH monitoring in saliva samples is reported. The potentiometric strip consists of a solid contact pH-selective and of a solidcontact ionogel reference electrode prepared on a dual screen printed substrate. The screen printing protocols, i.e., type of inks and number of deposits, were adjusted to relatively improve the batch reproducibility and the stability of the pH sensor. The pH of real saliva samples was monitored using the optimised potentiometric strip, and results were validated through parallel measurements with a standard laboratory method

Non invasive detection of biological fluids: a new perspective in monitoring pH in saliva and sodium in sweat

The chemical composition of body fluids contains crucial information about the state of health of an individual. While many efforts have been already directed toward real time analysis of blood and urine, there is still a pressing need for new solutions to non-invasively monitor other fluids like saliva and sweat1. Towards this aim, the main technological challenge is the development of devices that are at the same time low-cost, minimally invasive and wearable, so that they could be used for in situ and real-time monitoring of physiological conditions2. For example, continuous recording of sodium levels in sweat could be an informative tool to assist clinicians in prescribing a more personalised treatment of diseases such as Cystic Fibrosis3 and in assessing athletes’ performances4. Similarly, the monitoring of pH levels in saliva provides valuable information for the treatment of pathologies where physiological mouth conditions are compromised, like in Gastroesophageal Reflux Disease (GERD)5. Ion Selective Electrodes (ISEs) are potentiometric sensors designed to detect specific ions in blood and saliva. Using dual-screen printed electrodes as substrates, we were able to reduce their production cost, improve reproducibility, and combine pH5 and sodium ISEs with solid contact reference electrodes. In our design, the sensors will be interfaced to two miniaturized potentiometric platforms (WIXEL for pH and Tyndall Mote for sodium detection) that were wirelessly connected to a base station. For pH measurements, the device will be accommodated into a gum shield. For sodium detection instead, we will use a microfluidic channel to convey sweat to the electrodes. The mote communication platform was adapted so that it could be worn on the upper shoulder through a fiber strip

Yield and Quality of Essential Oils in Hemp Varieties in Different Environments

Due to its possible utilization in cosmetics, medicine and crop protection, as a valuable alternative to petrochemical-derived products, hemp essential oil is now considered a product with high value added and a promising marketing potential. This experiment was conducted with the aim of evaluating the effect of four different locations of Northern Italy during two years (four environments) and three hemp monoecious varieties on the production and quality of essential oils (EOs) obtained by inflorescences harvested at full flowering of female flowers. The highest inflorescence yield was obtained at Maiano 2017, where a superficial groundwater layer (1.5 m) was present, with values that ranged from 1.69 of Fedora to 2.06 t ha 121 of Futura. EOs production ranged between 3.4 and 4.9 L ha 121 , affected mainly by the variety effect. The terpene in EOs, very similar between varieties and environments, was mainly composed of sesquiterpenes (caryophillene and humulene, as the most abundant) rather than monoterpenes (\u3b1-pinene, \u3b2-myrcene and trans-\u3b2-ocimene, in particular). Phytocannabinoids, and in particular cannabidiol (CBD), were not removed from tissues by the steam during hydrodistillation, and if this is confirmed by further experiments, the residual biomass, now considered as waste, could assume significant importance as a source for further utilization

Dyslipidaemia and mortality in COVID-19 patients - a meta-analysis

Background: The prevalence and prognostic implications of pre-existing dyslipidaemia in patients infected by the SARS-CoV-2 remain unclear. Aim: To assess the prevalence and mortality risk in COVID-19 patients with pre-existing dyslipidaemia. Design: Systematic review and meta-Analysis. Methods: Preferred reporting items for systematic reviews and meta-Analyses guidelines were followed in abstracting data and assessing validity. We searched MEDLINE and Scopus to locate all the articles published up to 31 January 2021, reporting data on dyslipidaemia among COVID-19 survivors and non-survivors. The pooled prevalence of dyslipidaemia was calculated using a random-effects model and presenting the related 95% confidence interval (CI), while the mortality risk was estimated using the Mantel-Haenszel random-effect models with odds ratio (OR) and related 95% CI. Statistical heterogeneity was measured using the Higgins I2 statistic. Results: Of about 18 studies, enrolling 74 132 COVID-19 patients (mean age 70.6 years), met the inclusion criteria and were included in the final analysis. The pooled prevalence of dyslipidaemia was 17.5% of cases (95% CI: 12.3-24.3%, P &lt; 0.0001), with high heterogeneity (I2 = 98.7%). Pre-existing dyslipidaemia was significantly associated with higher risk of short-Term death (OR: 1.69, 95% CI: 1.19-2.41, P = 0.003), with high heterogeneity (I2 = 88.7%). Due to publication bias, according to the Trim-And-Fill method, the corrected random-effect ORs resulted 1.61, 95% CI 1.13-2.28, P &lt; 0.0001 (one studies trimmed). Conclusion: Dyslipidaemia represents a major comorbidity in about 18% of COVID-19 patients but it is associated with a 60% increase of short-Term mortality risk