Schottky junctions have been widely applied to facilitate charge carrier separation through the formation of an internal electric field (IEF). However, the notably restricted spatial distribution of the IEF weakens the promotion of intrinsic carrier separation. In this study, we unveil that Au nanoparticles (NPs) in the Au/CuTCPP(Fe) Schottky junction can manipulate the spin polarization of CuTCPP(Fe) to inhibit inner carrier recombination. Experimental investigations and theoretical calculations reveal that the introduction of Au NPs leads to an increased population of spin-polarized electrons, effectively suppressing inner charge carrier recombination in CuTCPP(Fe) by employing the spin mismatch between spin-polarized photoexcited carriers. Moreover, as a typical active site for the oxygen reduction reaction, the oxygen adsorption configuration on spin-polarized Fe single-atom sites in Au/CuTCPP(Fe) is further optimized, resulting in boosted interfacial reactions. Leveraging the thiocholine-induced poisoning of the active sites and the magnetic-enhanced photoelectric response, Au/CuTCPP(Fe) is harnessed to develop a photoelectrochemical biosensing platform for organophosphorus pesticides. This work offers a promising method for manipulating the spin polarization of semiconductors in heterojunctions to mitigate intrinsic charge carrier recombination.
Pullulanase (EC 3.2.1.41) belongs to the amylase family and is often used alone or in combination with other amylases in the industrial production of starch-based products. This enzyme is often required in industrial production because of its better stability. We here truncated the pullulanase gene from the deep-sea hydrothermal anaerobic archaeon Thermococcus siculi HJ21 and obtained Pul-HJΔ782, which is a member of the α-amylase family GH57. The results revealed that the optimum temperature for Pul-HJΔ782 was 100 °C, and its thermostability at 100 °C improved after truncation. Less than 15% of its enzyme activity was lost after 1 h of incubation at 100 °C, and 57% activity remained after 5 h of treatment. Truncation significantly improved the overall pH tolerance range of Pul-HJΔ782, and its stability in the pH range 4–8 was over 80% relative activity from an average of 60%. The sequence and structural model of Pul-HJΔ782 was analyzed, and its instability index was reduced significantly. Furthermore, the hydrolysates of the truncated and wild-type pullulanase were analyzed, and the enzymatic digestion efficiency of the truncated Pul-HJΔ782 was higher.
Semiconductor-based photoelectrochemical (PEC) biosensors have garnered significant attention in the field of disease diagnosis and treatment. However, the recognition units of these biosensors are mainly limited to bioactive macromolecules, which hinder the photoelectric response due to their insulating characteristics. In this study, we develop an in situ-sensitized strategy that utilizes a small-molecule probe at the interface of the photoelectrode to accurately detect α-glucosidase (α-Glu) activity. Silane, a prototype small-molecule probe, was surface-modified on graphitic carbon nitride to generate Si nanoparticles upon reacting with hydroquinone, the enzymatic product of α-Glu. The in situ formed heterojunction enhances the light-harvesting property and photoexcited carrier separation efficiency. As a result, the in situ-sensitized PEC biosensor demonstrates excellent accuracy, a low detection limit, and outstanding anti-interference ability, showing good applicability in evaluating α-Glu activity and its inhibitors in human serum samples. This novel in situ sensitization approach using small-molecule probes opens up new avenues for developing simple and efficient PEC biosensing platforms by replacing conventional biorecognition elements.
Perilla (Perilla frutescens L. Britt.) is an important oilseed and medicinal crop that frequently faces seasonal drought stress during seed germination, leading to a loss of dehydration tolerance (DT), which affects seed emergence and significantly reduces yield. DT has been successfully re-established for many species seeds. However, the physiological mechanisms and gene networks that regulate Perilla's response to DT loss remain unclear. Phenotypic analysis determined that the window for DT in Perilla seeds occurs at radicle lengths of 0–4 mm. Integrating physiological and transcriptomic analyses revealed that the loss of DT promotes the production of reactive oxygen species (ROS) and regulates oxidase activity and gene expression. This implies that DT may influence seed germination by modulating ROS activity. Four radicle length (i.e., 0, 1, 3, and 4 mm) stages were analyzed, and 262 differentially expressed genes (DEGs) were identified that responded to DT. The majority of these genes were associated with epigenetics, cell function, and transport mechanisms. Analysis of expression data shows that desiccation inhibits the signaling network of genes encoding small secreted peptides (SSPs) and receptor-like protein kinases (RLKs). Finally, a relevant network diagram of DT response was proposed. Based on this information, we have revealed the metabolism regulation maps of the four main pathways involving these DEGs (i.e., metabolic pathways, cell cycle, plant hormone signal transduction, and motor proteins). In conclusion, these findings deepen our understanding of gene network responses to DT during Perilla seed germination and provide potential target genes for the genetic improvement of drought resistance in this crop.
Recent years have witnessed ever-increasing achievements using Ti3C2 MXene quantum dots (Ti3C2 MQDs) and their vital contributions to fluorescent biosensing. However, the applicability and flexibility of most Ti3C2 MQD-based sensors are limited by their emission of a single blue wavelength. To address this issue, we present a facile strategy to utilize carbon dots as a model to construct a ratiometric fluorescent sensor based on fluorescence resonance energy transfer to quantitatively monitor crystal violet. The fabricated probe exhibited dual emission at 440 and 565 nm, respectively; when introducing crystal violet, the peak at 565 nm was quenched but that at 440 nm remained constant. Further aiming for portable, convenient, and on-site analysis, an innovative smartphone-assisted platform provides promising prospects for future in situ quantitation. This work creates a general strategy for constructing Ti3C2 MQD-based composite fluorescent systems, as well as suggesting great application potential in food security monitoring.
Ofloxacin (OFL) is widely used in animal husbandry and aquaculture due to its low price and broad spectrum of bacterial inhibition, etc. However, it is difficult to degrade and is retained in animal-derived food products, which are hazardous to human health. In this study, a simple and efficient method was developed for the detection of OFL residues in meat products. OFL coupled with amino magnetic beads by an amination reaction was used as a stationary phase. Aptamer AWO-06, which showed high affinity and specificity for OFL, was screened using the exponential enrichment (SELEX) technique. A fluorescent biosensor was developed by using AWO-06 as a probe and graphene oxide (GO) as a quencher. The OFL detection results could be obtained within 6 min. The linear range was observed in the range of 10–300 nM of the OFL concentration, and the limit of the detection of the sensor was 0.61 nM. Furthermore, the biosensor was stored at room temperature for more than 2 months, and its performance did not change. The developed biosensor in this study is easy to operate and rapid in response, and it is suitable for on-site detection. This study provided a novel method for the detection of OFL residues in meat products.
Abstract The severe environmental and human health hazards posed by organophosphorus compounds underscore the pressing need for advancements in their degradation and detection. However, practical implementation is impeded by prolonged degradation durations and limited efficiency. Herein, an effective interfacial modification approach is proposed involving the integration of photoactive Au nanoparticles (NPs) onto metal–organic frameworks, resulting in the synthesis of UiO‐66/Au NPs exhibiting enhanced hydrolysis activity under light excitation. Under illumination, UiO‐66/Au NPs trigger rapid hydrolysis of ethyl‐paraoxon within a mere 10‐min timeframe, yielding a discernible colorimetric response indicative of extensive hydrolysis. Mechanistic analyses reveal that Au NPs elevate the local catalytic microenvironment temperature of UiO‐66/Au NPs under light exposure, facilitating photo‐induced charge transfer that enhances the affinity between the Zr 6 clusters within UiO‐66/Au NPs and the hydrolytic substrate. These cooperative mechanisms significantly boost the hydrolytic efficiency of UiO‐66/Au NPs, resulting in a remarkable 17.8‐fold enhancement in catalytic performance. Leveraging the superior photo‐enhanced hydrolytic capabilities of UiO‐66/Au NPs, a colorimetric sensor is developed for the rapid degradation and detection of ethyl‐paraoxon, offering a practical and effective solution for addressing the degradation and detection challenges associated with organophosphorus compounds.
Developing a self-checking photoelectrochemical biosensor with dual photocurrent signals could efficiently eliminate false-positive or false-negative signals. Herein, a novel biosensor with dual photocurrent responses was established for the detection of acetylcholinesterase activity. To achieve photocurrent polarity-switchable behavior, the iodide/tri-iodide redox couple was innovatively introduced to simultaneously consume the photoexcited electrons and holes, which circumvents the inconvenience caused by the addition of different hole- and electron-trapping agents in the electrolyte. Importantly, benefiting from the high catalytic activity, the enhanced photoelectric responsivity can be realized after decorating the counter electrode with nickel single-atom catalysts, which promotes a more efficient iodide/tri-iodide redox reaction under low applied voltages. It is envisioned that the proposed photocurrent polarity switching system offers new routes to sensitive and reliable biosensing.
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