Switchable sniff-cam (gas-imaging system) based on redox reactions of alcohol dehydrogenase for ethanol and acetaldehyde in exhaled breath

Menstrual Cycle Matters in Host Attractiveness to Mosquitoes and Topical Repellent Protection

Human hosts exhibit remarkable variability in their attractiveness to mosquitoes, leading to differences in biting rates. It is essential to understand the factors behind this variability if we wish to develop more effective strategies for controlling the transmission of mosquito-borne diseases. While past studies have shed significant light on the forces shaping host attractiveness to mosquitoes, we continue to lack information about variation in attractiveness within individual hosts. For example, little attention has been paid to the potential impact of the menstrual cycle. Our study explored the relationship between the menstrual cycle, host attractiveness to mosquitoes, and the effectiveness of topical mosquito repellents. We found that mosquito landing rate was higher and repellent protection time was shorter during ovulation than during menstruation and the luteal phase. By beginning to clarify the intricate interplay between human physiology and mosquito behavior, our results contribute to the growing body of knowledge regarding the factors that affect within-individual variability in attractiveness to mosquitoes, which has implications for the efficacy of protection and disease prevention strategies.

Tandem Imaging of Breath Ethanol and Acetaldehyde Based on Multiwavelength Enzymatic Biofluorometry

Highly sensitive and selective imaging of human-borne volatile organic compounds (VOCs) enables an intuitive understanding of their concentrations and release sites. While multi-VOC imaging methods have the potential to facilitate step-by-step metabolic tracking and improve disease screening accuracy, no such system currently exists. In this study, we achieved simultaneous imaging of ethanol (EtOH) and acetaldehyde (AcH), the starting molecule and an intermediate metabolite of alcohol metabolism, using a multiwavelength VOC imaging system. The system employed alcohol dehydrogenase-catalyzed substrate oxidation (ADHOX) and reduction (ADHRD) reactions. The oxidation of EtOH by ADHOX in the presence of NAD+ produced NADH, which was subsequently oxidized by diaphorase (DP) with resazurin, leading to the resorufin formation, characterized by red fluorescence (excitation at 560 nm and fluorescence at 590 nm). Reduction of AcH by ADHRD consumed NADH, leading to a decrease in blue fluorescence (ex. 340 nm, fl. 490 nm). Meshes incorporating ADHOX-DP or ADHRD were arranged in tandem in front of a camera. Fluorescence images were captured, while a mixture of gaseous EtOH and AcH was applied by switching between two bandpass filters at 1 Hz. Each mesh exhibited selective responses to the target VOCs, with no significant impact on the dynamic range observed in either the single or tandem configurations (EtOH 1-300 ppm, AcH 0.2-5 ppm). The 90% response time was close after time-domain image differential analysis (EtOH = 26 s and AcH = 15 s). Furthermore, the system enabled simultaneous and quantitative imaging of EtOH and AcH concentrations in the breath after alcohol consumption. It also distinguished differences in alcohol metabolism based on the alcohol dehydrogenase 2 (ALDH2) activity, as indicated by the EtOH/AcH ratio (ALDH2 active vs nonactive: 120.9/0.71 ppm vs 129.2/1.99 ppm).

Luminescence Probes in Bio-Applications: From Principle to Practice

Bioanalysis based on optical imaging has gained significant progress in the last few decades. Luminescence probes are capable of detecting, monitoring, and tracing particular biomolecules in complex biological systems to figure out the roles of these molecules in organisms. Considering the rapid development of luminescence probes for bio-applications and their promising future, we have attempted to explore the working principles and recent advances in bio-applications of luminescence probes, in the hope of helping readers gain a detailed understanding of luminescence probes developed in recent years. In this review, we first focus on the current widely used luminescence probes, including fluorescence probes, bioluminescence probes, chemiluminescence probes, afterglow probes, photoacoustic probes, and Cerenkov luminescence probes. The working principles for each type of luminescence probe are concisely described and the bio-application of the luminescence probes is summarized by category, including metal ions detection, secretion detection, imaging, and therapy.

A Sensitive Micro Conductometric Ethanol Sensor Based on an Alcohol Dehydrogenase-Gold Nanoparticle Chitosan Composite

In this paper, a microconductometric sensor has been designed, based on a chitosan composite including alcohol dehydrogenase-and its cofactor-and gold nanoparticles, and was calibrated by differential measurements in the headspace of aqueous solutions of ethanol. The role of gold nanoparticles (GNPs) was crucial in improving the analytical performance of the ethanol sensor in terms of response time, sensitivity, selectivity, and reproducibility. The response time was reduced to 10 s, compared to 21 s without GNPs. The sensitivity was 416 µS/cm (v/v%)-1 which is 11.3 times higher than without GNPs. The selectivity factor versus methanol was 8.3, three times higher than without GNPs. The relative standard deviation (RSD) obtained with the same sensor was 2%, whereas it was found to be 12% without GNPs. When the air from the operator's mouth was analyzed just after rinsing with an antiseptic mouthwash, the ethanol content was very high (3.5 v/v%). The background level was reached only after rinsing with water.

Antarctic aldehyde dehydrogenase from Flavobacterium PL002 as a potent catalyst for acetaldehyde determination in wine

Latest solutions in biotechnologies and biosensing targeted cold-active extremozymes. Analysis of acetaldehyde as a relevant quality indicator of wine is one example of application that could benefit from using low-temperatures operating catalysts. In search of novel aldehyde dehydrogenases (ALDH) with high stability and activity at low temperatures, the recombinant S2-ALDH from the Antarctic Flavobacterium PL002 was obtained by cloning and expression in Escherichia coli BL21(DE3). Structural and phylogenetic analyses revealed strong protein similarities (95%) with psychrophilic homologs, conserved active residues and structural elements conferring enzyme flexibility. Arrhenius plot revealed a conformational shift at 30 °C, favoring catalysis (low activation energy) at lower temperatures. In addition to a broad substrate specificity with preference for acetaldehyde (Km = 1.88 mM), this enzyme showed a high tolerance for ethanol (15%) and several salts and chelators (an advantage for wine analysis), while being sensitive to mercury (I₅₀ = 1.21 µM). The neutral optimal pH (7.5) and the stability up to 40 °C and after lyophilization represent major assets for developing S2-ALDH-based sensors. An enzymatic electrochemical assay was developed for acetaldehyde detection in wines with proven accuracy in comparison with the reference spectrophotometric method, thus evidencing the potential of S2-ALDH as effective biocatalyst for industry and biosensing.

How emotional changes affect skin odor and its impact on others

The gas emanating from human skin is known to vary depending on one's physical condition and diet. Thus, skin gas has been gaining substantial scholarly attention as an effective noninvasive biomarker for understanding different physical conditions. This study focuses on the relationship between psychological stress and skin gas, which has remained unclear to date. It has been deduced that when participants were subjected to interviews confirmed as stressful by physiological indicators, their skin emitted an odor similar to stir-fried leeks containing allyl mercaptan and dimethyl trisulfide. This characteristic, recognizable odor appeared reproducibly during the stress-inducing situations. Furthermore, the study deduced that individuals who perceive this stress odor experience subjective tension, confusion, and fatigue (Profile of Mood States scale). Thus, the study findings indicate the possibility of human nonverbal communication through odor, which could enhance our understanding of human interaction.

Enzyme-embedded electrospun fiber sensor of hydrophilic polymer for fluorometric ethanol gas imaging in vapor phase

Non-invasive measurement of volatile organic compounds (VOCs) emitted from living organisms is a powerful technique for diagnosing health conditions or diseases in humans. Bio-based gas sensors are suitable for the sensitive and selective measurement of a target VOC from a complex mixture of VOCs. Conventional bio-based sensors are normally prepared as wet-type probes to maintain proteins such as enzymes in a stable state, resulting in limitations in the commercialization of sensors, their operating environment, and performance. In this study, we present an enzyme-based fluorometric electrospun fiber sensor (eFES) mesh as a gas-phase biosensor in dry form. The eFES mesh targeting ethanol was fabricated by simple one-step electrospinning of polyvinyl alcohol with an alcohol dehydrogenase and an oxidized form of nicotinamide adenine dinucleotide. The enzyme embedded in the eFES mesh worked actively in a dry state without pretreatment. Substrate specificity was also maintained, and the sensor responded well to ethanol with a sufficient dynamic range. Adjustment of the pH and coenzyme quantity in the eFES mesh also affected enzyme activity. The dry-form biosensor-eFES mesh-will open a new direction for gas-phase biosensors because of its remarkable performance and simple fabrication, which is advantageous for commercialization.

Exhaled breath biomarker sensing

This goal of this minireview is to introduce the reader to the area of research concerned with exhaled breath analysis for the purpose of detecting abnormal levels of physiologically-relevant chemical markers reflective of respiratory diseases. Two main two groups of sensing methods are reviewed: mass spectrometry and (bio)sensors. The discussion focuses on biosensor applications for EB and EBC analyses, which are presented in detail. The review finishes with conclusions and future perspectives, including recommendations for future near-term and long-term development of EBC biomarker sensing.

Adsorption/Combustion-type Micro Gas Sensors: Typical VOC-sensing Properties and Material-design Approach for Highly Sensitive and Selective VOC Detection

Highly sensitive and selective detection of various volatile organic compounds (VOCs) has been most needed in a wide range of fields, such as medical diagnosis, health supervision, industry-process control, and environmental monitoring. Since a semiconductor-type gas sensor is a typical promising candidate among various portable VOC-sensing devices, many efforts on developing these gas sensors are introduced in this article for the first time. Through some development stages, it has been well known that the temperature-modulated operation of gas sensors is one of effective ways to improve the magnitude of VOC responses. On the other hand, catalytic combustion-type gas sensors operated with a mode of pulse-driven heating were developed in the early 2000s, and they are named as "adsorption/combustion-type gas sensors" after their gas-sensing mechanism, based on the combustion of VOC adsorbates on the sensing material. The representative VOC-sensing properties of the adsorption/combustion-type gas sensors and recent material-design approach to achieve highly sensitive and selective VOC detection are summarized in this article.

Evaluation for regional difference of skin-gas ethanol and sweat rate using alcohol dehydrogenase-mediated fluorometric gas-imaging system (sniff-cam)

Skin gas that contains volatile metabolites (volatilome) is emanated continuously and is thus expected to be suitable for non-invasive monitoring. The aim of this study was to investigate the relationship between the regional difference of sweat rate and skin volatilome distribution to identify the suitable site to monitor metabolisms. In this study, we developed a biofluorometric gas-imaging system (sniff-cam) based on nicotinamide adenine dinucleotide (NAD)-dependent alcohol dehydrogenase (ADH) to visualize transcutaneous ethanol (EtOH) distribution. The EtOH distribution was converted to a fluorescence distribution of reduced NAD with autofluorescence property. First, we optimized the solution volume and concentration of the oxidized NAD, which was a coenzyme of ADH. Owing to the optimization, a two-dimensional distribution of EtOH could be visualized from 0.05-10 ppm with good sensitivity and selectivity. Subsequently, transcutaneous EtOH imaging and measurement of sweat rate were performed at the palm, dorsum of hand, and wrist of participants who consumed alcohol. Transcutaneous EtOH from all skin parts was imaged using the sniff-cam; the concentrations initially increased until 30 min after drinking, followed by a gradual decrease. Although the determined peak EtOH concentrations of typical subjects were approximately 1100 ± 35 ppb (palm), which were higher than 720 ± 18 ppb (dorsum) and 620 ± 13 ppb (wrist), the results of sweat rate suggested that the dorsum of hand and the wrist were appropriate sites. Finally, the sniff-cam could visualize the individual difference of alcohol metabolism capacity originating from aldehyde dehydrogenase phenotype by imaging transcutaneous EtOH.

Transcutaneous Blood VOC Imaging System (Skin-Gas Cam) with Real-Time Bio-Fluorometric Device on Rounded Skin Surface

A skin-gas cam that allows continuous imaging of transcutaneous blood volatile organic compounds (VOCs) emanated from human skin was developed. The skin-gas cam is able to reveal the relationship between the local skin conditions and transcutaneous blood VOCs in the field of volatile metabolomics (volatolomics). A ring-type ultraviolet (UV) light-emitting diode was mounted around a camera lens as an excitation light source, which enabled the simultaneous excitation and imaging of fluorescence. A nicotinamide adenine dinucleotide (NAD)-dependent alcohol dehydrogenase (ADH) was used to detect ethanol as a model sample. When gaseous ethanol was applied to an ADH-immobilized mesh that was wetted with an oxidized NAD solution placed in front of the camera, a reduced form of NAD (NADH) was produced through an ADH-mediated reaction. NADH emits fluorescence by UV excitation, and thus, the concentration distribution of ethanol was visualized by measuring the distribution of the fluorescence light intensity from NADH on the ADH-immobilized mesh surface. In this study, a new gas application method that mimicked the release mechanism of transcutaneous gas for quantification of the transcutaneous gas concentration was evaluated. Also, spatiotemporal changes of transcutaneous ethanol for various body parts were measured. As a result, we revealed a relationship between local skin conditions and VOCs that could not be observed previously. In particular, we demonstrated the facile measurement of transdermal gases from around the ear where capillaries are densely distributed below a thin stratum corneum.