Highly Sensitive and Selective Real-Time Breath Isoprene Detection using the Gas Reforming Reaction of MOF-Derived Nanoreactors

Recent advances in biosensors based on metal-oxide semiconductors system-integrated into bioelectronics

Metal-oxide semiconductors (MOSs) have emerged as pivotal components in technology related to biosensors and bioelectronics. Detecting biomarkers in sweat provides a glimpse into an individual's metabolism without the need for sample preparation or collection steps. The distinctive attributes of this biosensing technology position it as an appealing option for biomedical applications beyond the scope of diagnosis and healthcare monitoring. This review encapsulates ongoing developments of cutting-edge biosensors based on MOSs. Recent advances in MOS-based biosensors for human sweat analyses are reviewed. Also discussed is the progress in sweat-based biosensing technologies to detect and monitor diseases. Next, system integration of biosensors is demonstrated ultimately to ensure the accurate and reliable detection and analysis of target biomarkers beyond individual devices. Finally, the challenges and opportunities related to advanced biosensors and bioelectronics for biomedical applications are discussed.

Improved isoprene detection performance of Si-doped WO3 films deposited by sputtering and post-annealing

Si-doped WO3 films were sputtered at room temperature and then annealed in air at 500 °C. The Si doping resulted in structural distortion from space group P21/n to Pc. A high density of pores with a diameter of ∼20 nm was observed in the films, which is ideal for gas sensing applications because of the easy diffusion of gas. Isoprene sensitivity, which is defined as the resistance ratio measured in pure air and in air containing 5 ppm isoprene, was greatly improved by the Si doping. The films containing 6.3 at% Si showed the highest sensitivity of 7.7 at a working temperature of 325 °C. However, despite a lower sensitivity of 6.9 measured at 350 °C, the films exhibited better gas selectivity for isoprene over a range of reference gases, including methanol, ethanol, acetone, CO and CO2. The response and recovery times of the films were very short, being less than 1.5 and 3.0 seconds, respectively. Detailed characterization with a range of techniques verified that the increase in gas sensitivity in the Si-doped films was related to better oxygen adsorbability as a consequence of an increase in positively-charged oxygen vacancies introduced by the aliovalent substitution of W6+ by Si4+.

Mixed Potential Type Isoprene Sensor for the Application in Real-Time Monitoring of Biomarker Gases

Monitoring of isoprene in exhaled breath is expected to provide a noninvasive and painless method for dynamic monitoring of physiological and metabolic states during exercise. However, for real-time and portable detection of isoprene, gas sensors have become the best choice for gas detection technology, which are crucial to achieving the goal of anytime, anywhere, human-centered healthcare in the future. Here, we first report a mixed potential type isoprene sensor based on a Gd2Zr2O7 solid electrolyte and a CdSb2O6 sensing electrode, which enables sensitive detection for isoprene with sensitivities of -21.2 mV/ppm and -65.8 mV/decade in the range of 0.05-1 and 1-100 ppm. The sensing behavior of the sensor follows the mixed potential sensing mechanism and was further verified by the electrochemical polarization curves. The significant differentiation between the sensor response to exhaled breath of healthy individuals and simulated breath containing different concentrations of isoprene demonstrates the potential of the sensor for the detection of isoprene in exhaled breath. Simultaneously, monitoring of isoprene during exercise signifies the feasibility of the sensor in dynamic monitoring of physiological indicators, which is not only of great significance for optimizing training and guiding therapeutic exercise intervention in sporting scenarios but also expected to help further reveal the interaction between exercise, muscle, and organ metabolism in medicine.

A sensitive coumarin fluorescence sensor designed for isoprene detection and imaging research in plants

The release of isoprene by plants is considered to be an adaptation to the environment. Herein, a highly selective coumarin fluorescent probe (DMIC) was designed for detecting isoprene. When isoprene came into contact with the maleimide of DMIC, an electrophilic addition process took place. The powerful push-pull effect of DMIC was disrupted. Simultaneously, intramolecular charge transfer was initiated. This enabled DMIC to achieve rapid detection of isoprene within 5 min. Furthermore, excellent linearity was observed in the concentration range of 1-560 ppm (R2 = 0.996). A limit of detection is 1.6 ppm. DMIC was applied to in vitro studies of plant release of liberated isoprene. By monitoring the release of isoprene from different tree species throughout the day, the dynamics of isoprene release from plants throughout the day have been successfully revealed. In addition, the release of isoprene varied considerably among different tree species. In particular, the biocompatibility of DMIC allowed for the in vivo detection of isoprene using fluorescence imaging. The results successfully revealed the dynamics of isoprene release in plants under stress. The amount of isoprene that a plant produced increased with the severity of the stress it experienced. This suggested that the level of isoprene content in plants could be used as a preliminary indicator of the physiological health status of plants. This research demonstrates great potential for clarifying signal transduction in biological systems. It provided ideas for further understanding the biology of isoprene.

A review of physical, chemical and biological synthesis methods of bimetallic nanoparticles and applications in sensing, water treatment, biomedicine, catalysis and hydrogen storage

This article provides an in-depth analysis of various fabrication methods of bimetallic nanoparticles (BNP), including chemical, biological, and physical techniques. The review explores BNP's diverse uses, from well-known applications such as sensing water treatment and biomedical uses to less-studied areas like breath sensing for diabetes monitoring and hydrogen storage. It cites results from over 1000 researchers worldwide and >300 peer-reviewed articles. Additionally, the article discusses current trends, actionable recommendations, and the importance of synthetic analysis for industry players looking to optimize manufacturing techniques for specific applications. The article also evaluates the pros and cons of various fabrication methods, highlighting the potential of plant extract synthesis for mass production of capped BNPs. However, it warns that this method may not be suitable for certain applications requiring ligand-free surfaces. In contrast, physical methods like laser ablation offer better control and reactivity, especially for applications where ligand-free surfaces are critical. The report underscores the environmental benefits of plant extract synthesis compared to chemical methods that use hazardous chemicals and pose risks to extraction, production, and disposal. The article emphasizes the need for life cycle assessment (LCA) articles in the literature, given the growing volume of research on nanotechnology materials. This article caters to researchers at all stages and applies to various fields applying nanomaterials.