Carbon dioxide (CO2) released by plants can serve as a cue for regulating insect behaviors. Hyphantria cunea is a widely distributed forestry pest that may use CO2 as a cue for foraging and oviposition. However, the molecular mechanism underlying its ability to sense CO2 has not been elucidated. Our initial study showed that CO2 is significantly attractive to H. cunea adults. Subsequently, 44 H. cunea gustatory receptors (GRs) were identified using transcriptome data, and 3 candidate CO2 receptors that are specifically expressed in the labial palps were identified. In vivo electrophysiological assays revealed that the labial palp is the primary organ for CO2 perception in H. cunea, which is similar to findings in other lepidopteran species. By using the Xenopus oocyte expression system, we showed that the HcunGR1 and HcunGR3 co-expressions produced a robust response to CO2, but HcunGR2 had an inhibitory effect on CO2 perception. Finally, immunohistochemical staining revealed sexual dimorphism in the CO2-sensitive labial pit organ glomerulus (LPOG). Taken together, our results clarified the mechanism by which H. cunea sense CO2, laying the foundation for further investigations into the role of CO2 in the rapid spread of H. cunea.

Monitoring of carbon dioxide (CO2) body levels is crucial under several clinical conditions (e.g., human intensive care and acid-base disorders). To date, painful and risky arterial blood punctures have been performed to obtain discrete CO2 measurements needed in clinical setups. Although noninvasive alternatives have been proposed to assess CO2, these are currently limited to benchtop devices, requiring trained personnel, being tedious, and providing punctual information, among other disadvantages. To the best of our knowledge, the literature and market lack a wearable device for real-time, on-body monitoring of CO2. Accordingly, we have developed a microneedle (MN)-based sensor array, labeled as CO2-MN, comprising a combination of potentiometric pH- and carbonate (CO32-)-selective electrodes together with the reference electrode. The CO2-MN is built on an epidermal patch that allows it to reach the stratum corneum of the skin, measuring pH and CO32- concentrations directly into the interstitial fluid (ISF). The levels for the pH-CO32- tandem are then used to estimate the PCO2 in the ISF. Assessing the response of each individual MN, we found adequate response time (t95 < 5s), sensitivity (50.4 and -24.6 mV dec-1 for pH and CO32-, respectively), and stability (1.6 mV h-1 for pH and 2.1 mV h-1 for CO32-). We validated the intradermal measurements of CO2 at the ex vivo level, using pieces of rat skin, and then, with in vivo assays in anesthetized rats, showing the suitability of the CO2-MN wearable device for on-body measurements. A good correlation between ISF and blood CO2 concentrations was observed, demonstrating the high potential of the developed MN sensing technology as an alternative to blood-based analysis in the near future. Moreover, these results open new horizons in the noninvasive, real-time monitoring of CO2 as well as other clinically relevant gases.

Advances in gas sensors and open-source hardware are enabling new options for low-cost and light-weight gas sampling devices that are also robust and easy to use and construct. Although the number of studies investigating these sensors has been increasing in the last few years, they are still scarce with respect to agricultural applications. Here, we present a complete system for high-accuracy measurements of temperature, relative humidity, luminosity, and CO2 concentrations. The sensors suite is integrated on the previously developed HyperRail device (Lopez Alcala et al., 2019) - a reliable, accurate, and affordable linear motion control system. All measurements are logged with a location and time-stamp. The system was assembled from only off-the-shelf or 3D printable products. We deployed the system in an agricultural greenhouse to demonstrate the system capabilities.

The amygdala is mainly known for its role in the pathogenesis of anxiety and the initiation of fear responses. However, there is growing evidence showing that the amygdala\'s ability to respond to internal stimuli such as CO2 is limited, thereby challenging its role in the brain-behavior relationship. Based on these results and the strong inhibitory connections between the central nucleus of the amygdala and key brainstem areas regulating the reflexive respiratory responses to CO2, Feinstein et al. propose amygdala-driven apnea as a novel mechanism in the chemoreceptive origin of anxiety.

Fungi are exposed to various environmental variables during their life cycle, including changes in CO2 concentration. CO2 has the potential to act as an activator of several cell signaling pathways. In fungi, the sensing of CO2 triggers cell differentiation and the biosynthesis of proteins involved in the metabolism and pathogenicity of these microorganisms. The molecular machineries involved in CO2 sensing constitute a promising target for the development of antifungals. Carbonic anhydrases (CAs, EC 4.2.1.1) are crucial enzymes in the CO2 sensing systems of fungi, because they catalyze the reversible hydration of CO2 to proton and HCO3-. Bicarbonate in turn boots a cascade of reactions triggering fungal pathogenicity and metabolism. Accordingly, CAs affect microorganism proliferation and may represent a potential therapeutic target against fungal infection. Here, the inhibition of the unique β-CA (MpaCA) encoded in the genome of Malassezia pachydermatis, a fungus with substantial relevance in veterinary and medical sciences, was investigated using a series of conventional CA inhibitors (CAIs), namely aromatic and heterocyclic sulfonamides. This study aimed to describe novel candidates that can kill this harmful fungus by inhibiting their CA, and thus lead to effective anti-dandruff and anti-seborrheic dermatitis agents. In this context, current antifungal compounds, such as the azoles and their derivatives, have been demonstrated to induce the selection of resistant fungal strains and lose therapeutic efficacy, which might be restored by the concomitant use of alternative compounds, such as the fungal CA inhibitors.

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb3+/Ho3+. The attention has been paid to the analysis of the Yb3+→ Ho3+ energy transfer processed ions in fluoroindate glasses pumped by 976 nm laser diode. The most effective sensitization for 2 μm luminescence has been obtained in glass co-doped with 0.8YbF3/1.6HoF3. Further study in the mid-infrared spectral range (2.85 μm) showed that the maximum emission intensity has been obtained in fluoroindate glass co-doped with 0.1YbF3/1.4HoF3. The obtained efficiency of Yb3+→ Ho3+ energy transfer was calculated to be up to 61% (0.8YbF3/1.6HoF3), which confirms the possibility of obtaining an efficient glass or glass fiber infrared source for a MID-infrared (MID-IR) sensing application.

When compressed, the size of ordinary materials reduces. The opposite effect, when a material or system increases (decreases) its volume upon compression (decompression), is called Negative Compressibility (NC). NC is extremely rare, while being attractive for a wide range of applications. Here we demonstrate, by both experiments and MD simulations, a pronounced effect of volumetric NC in a system consisting of water, porous metal and CO2. This effect is achieved due to a new extrusion-adsorption cycle of water from-into a porous metal driven by a wetting-nonwetting transition due to the increase-decrease of CO2 pressure. The heterogeneous nature of such a system leads to unprecedented NC of up to ∼ 90% in a narrow pressure range, meaning that almost a double volume increase (decrease) upon compression (decompression) is achieved. As long as the wetting-nonwetting transition is achieved, the proposed approach is not limited to water and a specific porous metal. An example of the application of this phenomenon is miniature sensors, particularly for threshold CO2 pressure detection.

Monitoring carbon dioxide (CO2) levels is extremely important in a wide range of applications. Although metal oxide-based chemoresistive sensors have emerged as a promising approach for CO2 detection, the development of efficient CO2 sensors at low temperature remains a challenge. Herein, we report a low-temperature hollow nanostructured CeO2-based sensor for CO2 detection. We monitor the changes in the electrical resistance after CO2 pulses in a relative humidity of 70% and show the high performance of the sensor at 100 °C. The yolk-shell nanospheres have not only 2 times higher sensitivity but also significantly increased stability and reversibility, faster response times, and greater CO2 adsorption capacity than commercial ceria nanoparticles. The improvements in the CO2 sensing performance are attributed to hollow and porous structure of the yolk-shell nanoparticles, allowing for enhanced gas diffusion and high specific surface area. We present an easy strategy to enhance the electrical and sensing properties of metal oxides at a low operating temperature that is desirable for practical applications of CO2 sensors.

A nanocomposite of cross-linked bacterial cellulose-amino graphene/polyaniline (CLBC-AmG/PANI) was synthesized by covalent interaction of amino-functionalized graphene (AmG) AmG and bacterial cellulose (BC) via one step esterification, and then the aniline monomer was grown on the surface of CLBC-AmG through in situ chemical polymerization. The morphological structure and properties of the samples were characterized by using scanning electron microscopy (SEM), and thermal gravimetric analyzer (TGA). The CLBC-AmG/PANI showed good electrical-resistance response toward carbon dioxide (CO2) at room temperature, compared to the BC/PANI nanopaper composites. The CLBC-AmG/PANI sensor possesses high sensitivity and fast response characteristics over CO2 concentrations ranging from 50 to 2000 ppm. This process presents an extremely suitable candidate for developing novel nanomaterials sensors owing to easy fabrication and efficient sensing performance.

A water-air triboelectric nanogenerator (WATENG) is presented for CO2 sensing application. During the operation of WATENG, two independent charge transfers can be used to characterize the effect of force and humidity, respectively. Thus, the structure of WATENG provides a capability to eliminate these two major interferences in a triboelectric self-powered sensor. With the aid of the polyethylenimine (PEI) coating, WATENG can be used for CO2 sensing in both static and dynamic conditions. In static condition with a stable CO2 concentration, the CO2 sensing is characterized with respect to different relative humidity, and the sensing range can be up to 6000 ppm. In dynamic CO2 sensing of a pulse gas spray, due to the fast recovery of PEI surface reaction, the sensing range of dynamic situation can be broadened to 30,000 ppm. The self-powered and portable feature of WATENG is preferable as a self-powered amenity sensor for the construction of internet of the things (IoT) sensor networks in the future.