M.A.T.H: Methanol vapor analytics through handheld sensing platform

Activated carbon derived from wood biochar for Amperometric sensing of Ammonia for early screening of chronic kidney disease

Personalized medicine has emerged as an increasingly efficient and effective approach to addressing disease diagnosis and intervention. Ammonia is a waste product produced by the body during the digestion of protein. The requirement to develop an electrochemical sensing platform for monitoring skin ammonia levels holds great potential as an essential solution to pre-screen chronic kidney disease (CKD). In this research, we have manufactured an innovative electrochemical sensor by employing activated carbon derived from wood biochar as the signal transducer. We conducted a comprehensive analysis of the structural and morphological characteristics of the synthesized materials using various techniques. The hypothesized interaction was investigated using chronoamperometry as a transduction technique. To assess cross-reactivity, we conducted a study using common interferants or chemicals present in the environment. The data presented in this paper represents three replicates and is plotted with a 5 % error bar, demonstrating a 95 % confidence interval in the sensor response. In this study, we have elucidated the functionality and usefulness of a wearable microelectronic research prototype integrated with an HTC-activated carbon @RTIL-based electrochemical sensing platform for detecting ammonia levels released from the skin as a marker for chronic kidney disease screening. By enabling early detection and monitoring, these platforms can facilitate timely interventions, such as lifestyle modifications, medication adjustments, or referral to nephrology specialists. This proactive approach can potentially slow down disease progression, minimize the need for dialysis or transplantation, and ultimately improve the quality of life for CKD patients.

Recent Advances in Gas Detection Methodologies with a Special Focus on Environmental Sensing and Health Monitoring Applications─A Critical Review

With the expansion of the Internet-of-Things (IoT), the use of gas sensors in the field of wearable technology, smart devices, and smart homes has increased manifold. These gas sensors have two key applications─one is the detection of gases present in the environment and the other is the detection of Volatile Organic Compounds (VOCs) that are found in the breath. In this review, we focus systematically on the advancements in the field of various spectroscopic methods such as mass spectrometry-based analysis and point-of-care approach to detect VOCs and gases for environmental monitoring and disease diagnosis. Additionally, we highlight the development of smart sensors that work on the principle of electrochemical detection and provide examples of the same through an extensive literature review. At the end of this review, we highlight various challenges and future perspectives.

AuNP@ZeNose (ZIF-based electrochemical nose) for detection of flu biomarker in breath

A novel electrochemical sensor is reported for the detection of isoprene levels in breath using a ZIF-based electrochemical nose. This sensor incorporates a hybrid detection system using gold nanoparticles encapsulated inside the ZIF-8 moiety. Breath-based analysis is widely being used for monitoring the metabolic state of the body. It is associated with the change in the concentration of volatile organic compounds and inorganic gases released endogenously and can be tracked using breath as the sample. One such volatile organic compound, isoprene, has been correlated to the presence of influenza virus or respiratory inflammation. Analytical techniques such as powder X-ray diffraction, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and tunneling electron microscopy were used to understand the structural features of the composite. The electrochemical nose system uses chronoamperometry as the transduction mechanism to monitor the diffusion kinetics of the target analyte across the electrode-electrolyte interface. The presented work demonstrates isoprene sensing with high sensitivity and specificity and a detection limit of 10 parts per billion in air. We successfully demonstrate the functionality of the ZIF-based electrochemical nose for point-of-care screening of isoprene levels by developing a prototype device using a commercially available development board. We foresee that the developed sensing platform can help in early screening for the presence of influenza virus and help control the infection rate.

Reproducibility and reporting, the routes to progress in breath research - highlights from the Breath Biopsy Conference 2021

With the continued presence of COVID-19 worldwide, it has been a challenge for the breath research community to progress with clinical studies and travel restrictions have also limited the opportunities to meet up, share ideas and celebrate the latest advances. The Breath Biopsy Conference 2021 provided a much-needed opportunityoffered the chance to catch up with the latest breath research and to share the researchprogress that researchers in the community have been able to progress make in these difficult times. Limited opportunities for clinical research have provided opportunitiesled many in the field to look more closely at different methods for breath collection and have contributed to the growing calls for consistent standards in how results are reported, shared and even how breath studies themselves are carried out. As such, standardization was a key theme for this year's event and featured prominently in the keynotes, discussions and throughout many of the presentation sessions. With over 900 registrants, almost 400 live attendees and 16 speakers, the Breath Biopsy Conference continues to bring together breath research leaders from around the world. This article provides an overview of the highlights from this event.

E.Co.Tech-electrochemical handheld breathalyzer COVID sensing technology

Breathomics is widely emerging as a strategy for non-invasive diagnosis of respiratory inflammation. In this study, we have evaluated the metabolic signals associated with Coronavirus (SARS COV-2), mainly the release of nitric oxide in breath. We have demonstrated the utility of a breath analyzer-based sensor platform for the detection of trace amounts of this target species. The sensor surface is modified with Room Temperature Ionic Liquid (RTIL) that allows faster diffusion of the target gas and can be used for gas sensing application. A low limit of detection (LOD) of 50 parts per billion has been achieved with a 95% confidence interval for detection of nitric oxide.. This inhouse designed sensor is incorporated into a breath analyzer system that displays enhanced sensitivity, specificity, linearity, and reproducibility for NO gas monitoring. The developed sensor platform can detect target concentrations of NO ranging from 50 to 250 ppb, using 1-Ethyl-3-methylimidazolium Tetrafluoroborate ([EMIM]BF4) as RTIL and displays fast response time of 5 s, thereby allowing easy detection of the target gas species. The sensor successfully quantifies the diffusion current and charge modulations arising within the electrical double layer from the RTIL-NO interactions through DC-based chronoamperometry (CA). The subjects tested negative and positive are significantly different (p < 0.01). The prototype can potentially be used for human health monitoring and screening, especially during the pandemic due to its portability, small size, an embedded RTIL sensing element, integrability with a low-power microelectronic device, and an IoT interface.

Mg-doped InSnO nanofiber field-effect transistor for methanol gas detection at room temperature

Research on high-performance gas sensors for detecting toxic and harmful methanol gas is still a very important issue. For gas sensors, it is very important to be able to achieve low concentration detection at room temperature. In this work, we used the electrospinning method to prepare Mg-doped InSnO nanofiber field-effect transistors (FETs) methanol gas sensor. When the Mg element doping concentration is 2.3 mol.%, InSnO nanofiber FET exhibits excellent electrical properties, including higher mobility of 3.17 cm²V^-1s^-1, threshold voltage of 1.51 V, subthreshold swing of 0.42 V/decade, the excellent on/off current ratio is about 10⁸and the positive bias stress stability of the InSnO nanofiber FET through Mg doping has been greatly improved. In addition, the InSnMgO nanofiber FET gas sensor exhibits acceptable gas selectivity and sensitivity to methanol gas at room temperature. In the methanol gas sensor test at room temperature, when the methanol gas concentration is 60 ppm at room temperature, the response value of the InSnMgO nanofiber FET gas sensor is 81.92; and when the methanol concentration is 5 ppm, the response value is still 1.21. This work provides an effective and novel way to build a gas sensor at room temperature and use it to detect methanol gas at room temperature.

Bifunctional Metal Meshes Acting as a Semipermeable Membrane and Electrode for Sensitive Electrochemical Determination of Volatile Compounds

The monitoring of toxic inorganic gases and volatile organic compounds has brought the development of field-deployable, sensitive, and scalable sensors into focus. Here, we attempted to meet these requirements by using concurrently microhole-structured meshes as (i) a membrane for the gas diffusion extraction of an analyte from a donor sample and (ii) an electrode for the sensitive electrochemical determination of this target with the receptor electrolyte at rest. We used two types of meshes with complementary benefits, i.e., Ni mesh fabricated by robust, scalable, and well-established methods for manufacturing specific designs and stainless steel wire mesh (SSWM), which is commercially available at a low cost. The diffusion of gas (from a donor) was conducted in headspace mode, thus minimizing issues related to mesh fouling. When compared with the conventional polytetrafluoroethylene (PTFE) membrane, both the meshes (40 μm hole diameter) led to a higher amount of vapor collected into the electrolyte for subsequent detection. This inedited fashion produced a kind of reverse diffusion of the analyte dissolved into the electrolyte (receptor), i.e., from the electrode to bulk, which further enabled highly sensitive analyses. Using Ni mesh coated with Ni(OH)₂ nanoparticles, the limit of detection reached for ethanol was 24-fold lower than the data attained by a platform with a PTFE membrane and placement of the electrode into electrolyte bulk. This system was applied in the determination of ethanol in complex samples related to the production of ethanol biofuel. It is noteworthy that a simple equation fitted by machine learning was able to provide accurate assays (accuracies from 97 to 102%) by overcoming matrix effect-related interferences on detection performance. Furthermore, preliminary measurements demonstrated the successful coating of the meshes with gold films as an alternative raw electrode material and the monitoring of HCl utilizing Au-coated SSWMs. These strategies extend the applicability of the platform that may help to develop valuable volatile sensing solutions.

ZEUS (ZIF-based electrochemical ultrasensitive screening) device for isopentane analytics with focus on lung cancer diagnosis

Breath analytics is currently being explored for the development of point-of-care devices in non-invasive disease detection. It is based on the measurement of volatile organic compounds (VOCs) and gases that are produced by the body because of the metabolic pathways. The levels of these metabolites vary due to alteration in the endogenous oxidative stress-related metabolic pathways and can be correlated to understand the underlying disease condition. The levels of exhaled hydrocarbons in human breath can be used to design a rapid, easy to use method for lung cancer detection. This work outlines the development of an electrochemical sensing platform that can be used for the non-invasive diagnosis of lung cancer by monitoring isopentane levels in breath. This electrochemical sensor platform involves the use of [BMIM]BF4@ZIF-8 for sensing the target analyte. This synthesized nanocomposite offers advantages for gas sensing applications as it possesses unique properties such as an electrochemically active Room Temperature Ionic Liquid (RTIL) and a crosslinking Metal Organic Framework (MOF) that provides increased surface area for gas absorption. This is the first report of a hydrocarbon-based sensor platform developed for lung cancer diagnosis. The developed sensor platform displays sensitivity and specificity for the detection of isopentane up to 600 parts-per-billion. We performed structural and morphological characterization of the synthesized nanocomposite using various analytical techniques such as PXRD, FESEM, FTIR, and DLS. We further analyzed the electrochemical activity of the synthesized nanocomposite using a standard glassy carbon electrode. The application of the nanocomposite for isopentane sensing was done using a commercially available carbon screen printed electrode. The results so obtained helped in strengthening our hypothesis and serve as a proof-of-concept for the development of a breathomics-enabled electrochemical strategy. We illustrated the specificity of the developed nanocomposite by cross-reactivity studies. We envision that the detection platform will allow sensitive and specific sensing of isopentane levels such that it can used for point of care applications in noninvasive and early diagnosis of lung cancer, thereby leading to its early treatment and decrease in mortality rate.

ZENose (ZIF-Based Electrochemical Nose) Platform for Noninvasive Ammonia Detection

Breathomics is a widely emerging tool for noninvasive disease diagnosis and focuses on the detection of various levels of volatile organic compounds and inorganic gases present in human breath. One of the rapid, easy-to-use, and noninvasive detection methods being investigated is a system that can measure exhaled breath ammonia levels and can be correlated to the functional state of protein metabolic pathways and the renal functioning system. In this work, we have demonstrated the development of an electrochemical nose system using ferrocene encapsulated into zeolitic imidazole framework, Fc@ZIF-8, which can be successfully used for the detection of ammonia levels in breath. This is the first report of an electrochemical gas sensor platform that uses a faradaic probe (that is ferrocene) encapsulated into a metal-organic framework cavity used for disease diagnosis by monitoring the levels of the target gas and can be used for breathomics applications. This work demonstrates that low levels of ammonia gas (up to 400 ppb) can be detected with high sensitivity and specificity. The morphological and structural characterization of the novel, synthesized Fc@ZIF-8 nanocomposite has been performed using powder X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, ultraviolet-visible spectroscopy, and dynamic light scattering. Electrochemical characterization of the material has been performed using a standard glassy carbon electrode, and further application of the material has been shown using the in-house designed and reported spiral electrochemical notification coupled electrode, used for ammonia gas sensing. Cross-reactivity studies have also been performed to demonstrate sensor specificity toward the target gas. We demonstrate the first of its kind electrochemical bifunctional probe platform that can be used for sensing ammonia levels in breath, with high sensitivity and specificity, due to the hybrid material system-zinc-imidazole framework 8 (having excellent physisorption properties) and ferrocene (acting as a redox mediator). We envision that such a sensing system will allow noninvasive and early diagnosis of chronic kidney disease, thus leading to early treatment and a decrease in the mortality rate.