Diffusion-modulated colorimetric sensor for continuous gas detection.

Due to their high sensitivity and selectivity, low cost, and good compatibility for sensor array integration, colorimetric gas sensors are widely used in hazardous gas detection, food freshness assessment, and gaseous biomarker identification. However, colorimetric gas sensors are usually designed for one-time discrete measurement because the sensing materials are entirely exposed to analytes during the sensing process. The fast consumption of sensing materials limits colorimetric sensors' applications in continuous analytes monitoring, increases the operation complexity and brings challenges for calibration. In this work, we reported a novel sensor design to prolong the lifetime of colorimetric gas sensors by engineering the gas diffusion process to preserve the sensing materials. We compared two geometries for gas diffusion control in a sensing matrix through simulation and experiment on an ammonia sensing platform. We found that the 2-dimensional gas diffusion geometry enabled a better sensor performance, including more stable and higher sensitivity and a more linear response to ammonia concentration compared to 1-dimensional gas diffusion geometry. We also demonstrated the usability of this diffusion-modulated colorimetric sensor for continuous environmental ammonia monitoring.

Characterization of Copper/Zinc Superoxide Dismutase Activity on Phascolosoma esculenta (Sipuncula: Phascolosomatidea) and Its Protection from Oxidative Stress Induced by Cadmium.

Phascolosoma esculenta, an economically important species inhabiting the high tide areas of the intertidal zone, is particularly sensitive to water pollution. Considering its potential as a bioindicator, studies on the ecotoxicology of P. esculenta are imperative. The toxic effects of cadmium (Cd) were analyzed by exposing P. esculenta to different concentrations of Cd (6, 24, 96 mg/L). In this study, the changes in the antioxidative indexes of total superoxide dismutase (T-SOD), glutathione s-transferase (GST), reduced glutathione (GSH), and microscale malondialdehyde (MDA) were recorded. Copper/zinc superoxide dismutase (Cu/Zn SOD) is one of the most important free radical scavenging members. To reveal the antioxidative function of P. esculenta, an important member of the antioxidative system, designated Pe-Cu/Zn SOD, was cloned and analyzed. Phylogenic analysis revealed that Pe-Cu/Zn SOD was located in the invertebrate evolutionary branch of intracellular Cu/Zn SOD (icCu/Zn SOD). The quantitative real-time polymerase chain reaction results showed that Pe-Cu/Zn SOD messenger ribonucleic acid was widely expressed in all tissues examined. The highest expression levels in coelomic fluid after Cd exposure indicated its function in the stress response. Using a prokaryotic expression system, we obtained a Pe-Cu/Zn SOD recombinant protein, which enhanced the heavy metal tolerance of Escherichia coli. In vivo assays also confirmed that the Pe-Cu/Zn SOD recombinant protein had an antioxidative and free radical scavenging ability. A Cd toxicity experiment, in which purified Pe-Cu/Zn SOD protein was injected into the body cavities of P. esculenta, showed that the reactive oxygen species content in the coelomic fluid of the experimental group was significantly lower compared with the control group. These results suggest that Pe-Cu/Zn SOD played a role in Cd detoxification by chelating heavy metal ions and scavenging reactive oxygen free radicals, and that P. esculenta could be used as a bioindicator to evaluate heavy metal pollution.

Molecular characterization, dynamic transcription, and potential function of KIF3A/KIF3B during spermiogenesis in Opsariichthys bidens.

Spermiogenesis is the final phase of spermatogenesis, wherein the spermatids differentiate into mature spermatozoa via complex morphological transformation. In this process, kinesin plays an important role. Here, we observed the morphological transformation of spermatids and analyzed the characterization, dynamic transcription, and potential function of kinesin KIF3A/KIF3B during spermiogenesis in Chinese hook snout carp (Opsariichthys bidens). We found that the full-length cDNAs of O. bidens kif3a and kif3b were 2544 and 2806 bp in length comprising 119 bp and 259 bp 5' untranslated region (UTR), 313 bp and 222 bp 3' UTR, and 2112 bp and 2325 bp open reading frame encoding 703 and 774 amino acids, respectively. Ob-KIF3A/KIF3B proteins have three domains, namely N-terminal head, coiled-coil stalk, and C-terminal tail, and exhibit high similarity with homologous proteins in vertebrates and invertebrates. Ob-kif3a/kif3b mRNAs were ubiquitously expressed in all tissues examined, with the highest expression in the brain and stage-IV testis. Immunofluorescence results showed that Ob-KIF3A was co-localized with tubulin and the mitochondria. Particularly, in early spermatids, Ob-KIF3A, tubulin, and the mitochondrial signals were evenly distributed in the cytoplasm, whereas in middle spermatids, they were distributed around the nucleus. In the late stage, the signals were concentrated on one side of the nucleus, where the tail is formed, whereas in mature sperms, they were detected in the midpiece and flagellum. These results indicate that Ob-KIF3A/KIF3B may participate in nuclear reshaping, flagellum formation, and mitochondrial aggregation in the midpiece during spermiogenesis.

Molecular cloning, characterisation and expression analysis of the vitellogenin genes vtgAo1 and vtgC during ovarian development in Chinese hook snout carp Opsariichthys bidens.

Vitellogenesis is essential for oocyte maturation. Vitellogenin (Vtg), a yolk precursor protein, plays an important role in oogenesis and vitellogenesis. Chinese hook snout carp Opsariichthys bidens is an economically important freshwater fish in China whose reproductive and developmental biology are not well understood. In this study, we undertook histological analysis to examine ovary development and oogenesis in O. bidens. The ovaries were divided into Stages II-V and oocytes were divided into perinuclear oocytes, cortical alveoli oocytes, vitellogenic oocytes and mature oocytes. Full-length cDNA sequences were cloned of two vtg genes from the liver of O. bidens, namely Ob-vtgAo1 and Ob-vtgC. Ob-vtgAo1 and Ob-vtgC cDNA are made up of 4136 and 4392 bases respectively and encode proteins containing 1335 and 1250 amino acids respectively. Ob-vtgAo1 contains three yolk protein domains: lipovitellin heavy chain (LvH), phosvitin (Pv) and lipovitellin light chain (LvL), whereas Ob-VtgC contains LvH and LvL, which are incomplete Vtgs. Ob-vtgAo1 and Ob-vtgC mRNA expression was significantly higher in the liver of O. bidens than in all other tissues. In oocytes of Stage II-III ovaries, yolk granules are almost absent and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is low. At Stage IV, the oocyte is filled with yolk granules and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is significantly increased. Collectively, these findings help us better understand vitellogenesis in O. bidens.

Gradient-Based Colorimetric Array Sensor for Continuous Monitoring of Multiple Gas Analytes.

Colorimetry is widely used in chemical sensing due to its high sensitivity and high selectivity. However, most colorimetric sensors are one-time use because the color-producing reactions or bindings are usually irreversible. In addition, traditional colorimetric sensors like the detection tubes are bulky and packed individually, making parallel sensing of multiple analytes difficult. Here, we demonstrate a gradient-based colorimetric array sensor (GCAS) to overcome these limitations. Different colorimetric sensing elements are inkjet-printed as parallel straight lines on a porous substrate. Lateral transport of analytes across the substrate creates color gradients on the sensing elements. The color gradients shift along the transport direction over time, and GCAS tracks the gradient shifts and converts them into analyte concentrations in real time. Using a low-cost complementary metal-oxide semiconductor imager, we show detection of three air pollutants using a single GCAS chip and 24 h continuous monitoring of ambient ozone.

Cloning, Functional Characterization and Response to Cadmium Stress of the Thioredoxin-like Protein 1 Gene from Phascolosoma esculenta.

Cadmium (Cd) is a heavy metal toxicant and is widely distributed in aquatic environments. It can cause excessive production of reactive oxygen species (ROS) in the organism, which in turn leads to a series of oxidative damages. Thioredoxin (Trx), a highly conserved disulfide reductase, plays an important role in maintaining the intracellular redox homeostasis in eukaryotes and prokaryotes. Phascolosoma esculenta is an edible marine worm, an invertebrate that is extensively found on the mudflats of coastal China. To explore the molecular response of Trx in mudflat organisms under Cd stress, we identified a new Trx isoform (Trx-like protein 1 gene) from P. esculenta for the first time, designated as PeTrxl. Molecular and structural characterization, as well as multiple sequence and phylogenetic tree analysis, demonstrated that PeTrxl belongs to the Trx superfamily. PeTrxl transcripts were found to be ubiquitous in all tissues, and the highest expression level occurred in the coelomic fluid. Exposure to three sublethal concentrations of Cd resulted in the upregulation and then downregulation of PeTrxl expression levels over time in coelomic fluid of P. esculenta. The significant elevation of PeTrxl expression after 12 and 24 h of Cd exposure at 6 and 96 mg/L, respectively, might reflect its important role in the resistance to Cd stress. Recombinant PeTrxl (rPeTrxl) showed prominent dose-dependent insulin-reducing and ABTS free radical-scavenging abilities. After exposure to 96 mg/L Cd for 24 h, the ROS level increased significantly in the coelomic fluid, suggesting that Cd induced oxidative stress in P. esculenta. Furthermore, the injection of rPeTrxl during Cd exposure significantly reduced the ROS in the coelomic fluid. Our data suggest that PeTrxl has significant antioxidant capacity and can protect P. esculenta from Cd-induced oxidative stress.

Cytological features of spermatogenesis in Opsariichthys bidens (Teleostei, Cyprinidae).

Spermatogenesis is important for male fertility, but has not been well-studied in Opsariichthys bidens, an economically important freshwater fish in China. In this study, there was investigation of the cytological features of spermatogenesis in O. bidens using light microscopy, transmission electron microscopy, and immunofluorescence detection of microtubules. O. bidens has tubular testis. Spermatogenesis in O. bidens is of the cystic type, in which the spermatogenic cells develop into spermatozoa in cysts. There was asynchronous development of primary spermatocytes within a single cyst. Spermiogenesis was classified as Type I, which develops into a Type I aquasperm with an oval nucleus, a small and simple midpiece, a flagellum and no acrosome. There was a nuage in spermatogonia, spermatocytes, and spermatids in different developmental stages of spermatids which may have important functions in fish spermatogenesis. Furthermore, microtubule dynamics may be involved in spermatid reshaping, material transport, and polar distribution of organelles during spermiogenesis.

Light-Controlled Configurable Colorimetric Sensing Array.

Colorimetry is a popular gas-sensing platform, but it is typically limited to one-time use only. Here, we introduce a light-controlled configurable colorimetric sensing array to overcome this limitation. It features a photoactivated reaction between an analyte and a sensing material, such that sensing of an array element can be turned on and off with light. By sequential turning on of each array element, the sensor array can be used multiple times as determined by the number of array elements. This is analogous to a data storage device, which lasts until every storage element is used up. The total number of array elements and the area of each array element are configurable with light. With use of a smartphone screen as a programmable light source, we applied the sensing platform to the detection of oxygen gas and studied the relationship between sensitivity, noise, detection time, and array size. The relationship can be used to configure the array to meet the specifications of different applications.

Gradient-Based Colorimetric Sensors for Continuous Gas Monitoring.

Colorimetry detects a color change resulted from a chemical reaction or molecular binding. Despite its widespread use in sensing, continuous monitoring of analytes with colorimetry is difficult, especially when the color-producing reaction or binding is irreversible. Here, we report on a gradient-based colorimetric sensor (GCS) to overcome this limitation. Lateral transport of analytes across a colorimetric sensor surface creates a color gradient that shifts along the transport direction over time, and GCS tracks the gradient shift and converts it into analyte concentration in real time. Using a low cost complementary metal-oxide semiconductor imager and imaging processing algorithm, we show submicrometer gradient shift tracking precision and continuous monitoring of ppb-level ozone.

High Performance Colorimetric Carbon Monoxide Sensor for Continuous Personal Exposure Monitoring.

Carbon monoxide (CO) is a highly poisonous gas, which can cause serious health risk. CO monitoring helps protect us from excessive exposure at home and in the workplace, and reduce occupation-related health risks for workers. Conventional electrochemical and metal oxide semiconductors (MOS) based CO sensors have been widely used, but the drawbacks such as poor selectivity and calibration burden also limit their applications, e.g., as wearable exposure monitors. Aiming at the reliable, miniaturized, and easy-to-use personal exposure device development, we report a colorimetric CO sensing platform, which achieves a detection limit of 1 ppm, dynamic range of 0-500 ppm, and high selectivity to CO over common interferents in air, such as CO2, NO2, SO2, and O3. This optical sensing platform can be expanded to other air pollutants by adding other chemical sensing probes. We believe the new sensing platform we introduced can provide a potential high performance sensing unit for wearable personal exposure assessment devices.

Hydrogen-incorporated TiS2 ultrathin nanosheets with ultrahigh conductivity for stamp-transferrable electrodes.

As a conceptually new class of two-dimensional (2D) materials, the ultrathin nanosheets as inorganic graphene analogues (IGAs) play an increasingly vital role in the new-generation electronics. However, the relatively low electrical conductivity of inorganic ultrathin nanosheets in current stage significantly hampered their conducting electrode applications in constructing nanodevices. We developed the unprecedentedly high electrical conductivity in inorganic ultrathin nanosheets. The hydric titanium disulfide (HTS) ultrathin nanosheets, as a new IGAs, exhibit the exclusively high electrical conductivity of 6.76 × 10(4) S/m at room temperature, which is superior to indium tin oxide (1.9 × 10(4) S/m), recording the best value in the solution assembled 2D thin films of both graphene (5.5 × 10(4) S/m) and inorganic graphene analogues (5.0 × 10(2) S/m). The modified hydrogen on S-Ti-S layers contributes additional electrons to the TiS2 layered frameworks, rendering the controllable electrical conductivity as well as the electron concentrations. Together with synergic advantages of the excellent mechanical flexibility, high stability, and stamp-transferrable properties, the HTS thin films show promising capability for being the next generation conducting electrode material in the nanodevice fields.

Giant moisture responsiveness of VS2 ultrathin nanosheets for novel touchless positioning interface.

Utilizing a thin film of VS(2) ultrathin nanosheets with giant and fast moisture responsiveness, a brand-new model of moisture-based positioning interface is put forward here, by which not only the 2D position information of finger tips can be acquired, but also the relative height can be detected as the third dimensionality, representing a promising platform for advanced man-machine interactive systems.

Metallic few-layered VS2 ultrathin nanosheets: high two-dimensional conductivity for in-plane supercapacitors.

With the rapid development of portable electronics, such as e-paper and other flexible devices, practical power sources with ultrathin geometries become an important prerequisite, in which supercapacitors with in-plane configurations are recently emerging as a favorable and competitive candidate. As is known, electrode materials with two-dimensional (2D) permeable channels, high-conductivity structural scaffolds, and high specific surface areas are the indispensible requirements for the development of in-plane supercapacitors with superior performance, while it is difficult for the presently available inorganic materials to make the best in all aspects. In this sense, vanadium disulfide (VS(2)) presents an ideal material platform due to its synergic properties of metallic nature and exfoliative characteristic brought by the conducting S-V-S layers stacked up by weak van der Waals interlayer interactions, offering great potential as high-performance in-plane supercapacitor electrodes. Herein, we developed a unique ammonia-assisted strategy to exfoliate bulk VS(2) flakes into ultrathin VS(2) nanosheets stacked with less than five S-V-S single layers, representing a brand new two-dimensional material having metallic behavior aside from graphene. Moreover, highly conductive VS(2) thin films were successfully assembled for constructing the electrodes of in-plane supercapacitors. As is expected, a specific capacitance of 4760 µF/cm(2) was realized here in a 150 nm in-plane configuration, of which no obvious degradation was observed even after 1000 charge/discharge cycles, offering as a new in-plane supercapacitor with high performance based on quasi-two-dimensional materials.