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Early detection and analysis of pathogens in food are an effective way to curb food poisoning. Traditional detection methods require complex sample pretreament and high costs, and are not easy to implement point-of-care testing (POCT) for food safety. By preparing a patch of vitrified silk fibroin hollow microneedle array patch (SF-HMAP) and integrating it with a patterned paper-based chip using a 3D printing technology and a double-printed die fabrication process, a conceptual sensor in the form of a microneedle array paper chip has been successfully developed. During the preparation of the sensor, the vitrified SF-HMAP with a suitable diameter and height exhibits a complete and homogeneous structure and excellent mechanical properties, thus being able to meet the puncture detection of various food products. Meanwhile, rice paper with good color intensity and uniformity was selected as the patterned paper-based chip sensing layer and assembled with vitrified SF-HMAP to form a sensor, which can quickly absorb and transmit liquid into the solid gel within 9 min. To validate the practicality of the conceptual sensor, the loading of copper nanoclusters (Cu NCs) probes in a patterned paper-based sensing layer enabled continuous visual fluorescence monitoring of histamine produced during the storage of fresh pork and fresh shrimp and color comparison with standard colorimetric cards for histamine detection, allowing semi-quantitative colorimetric detection of histamine in actual samples. The proposed portable conceptual sensor is adjustable and versatile, and offers a novel idea and approach for food safety detection. • A portable colorimetric sensor for histamine was prepared based on paper chip. • The conceptual sensor was validated for raw meat-mimic environment. • The sensor enables continuous monitoring of histamine in pork and shrimp. • The sensor promises to be a powerful tool for point-of-care testing of food safety. [ABSTRACT FROM AUTHOR]

• A microfluidic system for simultaneous and large scale multi-size 3D tumor manipulation and analysis was developed. • Controllable and massive production of biomimetic multi-size tumors was established in the single microfluidic device. • The system allows highly efficient multi-size tumor formation with quantitative-uniformity. • Orthogonal drug resistance determination of multi-size tumors was accomplished in throughput in the single device. The establishment of a miniaturized platform capable of microscale control for sequential, coordinated, and throughput biomimetic tumor manipulation and analysis offer a high degree of biological and clinical relevance to cancer therapy and pharmaceutical research. In this study, we developed a microfluidic system with well-established microwell arrays and simple double-layer composition that allows massive fabrication of biomimetic multi-size 3D tumors and their simultaneous manipulation and orthogonal analysis. Serial manipulations including cell localization, array-like self-assembly/cultivation, and dynamic analysis of different types of 3D tumors, were accomplished in the microfluidic device. We demonstrated that the microfluidic platform is stable and throughput cell trapping and tumor generation with quantity uniform. Furthermore, on-chip monitoring and throughput analysis of tumor phenotypes and responses to culture and different chemotherapies were also achieved in the device. The microfluidic advancement offers a new methodological approach for the development of high-performance and multifunctional 3D tumor systems and for tissue-mimicking cancer research and therapy evaluation. This microfluidic platform, which has the capability of multiple control in time and space, holds great potential for applications in the fields of tumor biology, tissue engineering, and clinical medicine. [ABSTRACT FROM AUTHOR]

Microfluidic mixings create considerable opportunities for microscale exploration of biomacromolecule function and local reaction kinetics. However, a robust and efficient way for localized mixing performance is not yet well established. In this study, we describe a simple and reliable method for rapid, stable, and controllable in situ mixing using a single-layer acoustofluidic system with a microneedle. We developed the single microstructure for region-confined mixing, which can be controlled dynamically by intentional acoustic activation. Various acoustofluidic impacts including driving frequency, microstructure design, driving voltage, and flow control on homogeneous mixing were systematically investigated. The microneedle-based device allows a fast (∼ 85 ms) mixing operation. Robust and high reusability of acoustofluidic system was experimentally demonstrated with up to 200 times of repetitive mixing and 100 min of continuous mixing. Furthermore, the proof-of-concept applications including real-time characterization of fluorescein quenching and β -glucuronidase-catalyzed hydrolysis of 4-methyl-umbelliferyl- β - d -glucuronide were successfully accomplished in the in situ mixing platform. We believe this microfluidic system could be suitable for investigation of different instantaneous chemical/biochemical events associated with various molecular interactions and reactions. Also, the acoustofluidic approach is potentially valuable to the development of mixing-based integrated microfluidic systems for applications in molecular science and life science. [ABSTRACT FROM AUTHOR]

The sensitive detection and quantification of heavy and transition metal ions are particularly important. Among them, mercury(II) (Hg 2+ ) and silver(I) (Ag + ) ions, as the most ubiquitous heavy metal ion pollutants, are difficult to discriminate in the same system because of their similar reactions and coordination abilities. Herein, we designed and synthesized a “turn-on” chemosensor, RBTP , which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit to the ortho -position of the phenolic hydroxy of rhodol. RBTP showed a sensitive dual-channel fluorescence-enhanced response to Hg 2+ and Ag + at 595 and 520 nm with low detection limits of 0.27 and 0.45 μM, respectively. Studies of their sensing mechanism indicated that the Hg 2+ -induced orange fluorescence at 595 nm originates from an irreversible Hg 2+ -promoted oxadiazole forming reaction and the Ag + -induced green fluorescence at 520 nm originates from special molecular packing of the RBTP -Ag + complex. Furthermore, the potential of probe RBTP as practical biological imaging agents was further confirmed in HepG2 cells. Simultaneously, RBTP exhibited remarkable solid-state luminescence with an aggregation-induced emission (AIE) feature. The AIE mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations. [ABSTRACT FROM AUTHOR]

Pesticide pollution has become a severe challenge for harming food quality and human safety. Therefore, it's urgent to develop sensitive methods to detect and analyse pesticides. Herein, we successfully developed a new turn-on fluorescent chemosensor (TPE-4P), a tetraphenyl ethylene derivative modified with four pillar[5]arenes, which could sensitively, selectively, and rapidly detect the pesticide paraquat. In our study, we took full advantage of both the host-guest strategy and aggregation-induced emission (AIE) to achieve fluorescent enhancement of the chemosensor for paraquat, in which four pillar[5]arenes as the recognition units can selectively capture paraquat. The formation of the supramolecular complexes based on the interlaced host-guest interactions effectively restricted the intramolecular single-bond rotation and skeletal vibration, resulting in the intensive fluorescent emission. The detection limit for paraquat was low enough to reach 154.1 nM, and the detection time was short enough to meet the rapid detection conditions. Moreover, the test strips loaded- TPE-4P facilitated the detection process and achieved the semi-quantitative analysis for paraquat in real spiked samples. In addition, TPE-4P could respond to paraquat in living zebrafish obviously. These results suggest that the cooperation of host-guest and AIE chemistry could become useful for the design to detect some appropriate organic molecules. [Display omitted] • A turn-on chemosensor was synthesized based on TPE and pillar[5]arene. • The sensor can rapidly, selectively, and sensitively detect pesticide paraquat through host-guest and AIE chemistry. • The sensor can be used in visual determination of paraquat in real samples and zebra fish. • The fabricated test strips can quantitatively detect paraquat. • The cooperation of host-guest and AIE chemistry is useful for the design of chemosensors. [ABSTRACT FROM AUTHOR]

Magnetic molecularly imprinted (MMIP) particle-based electrochemical sensors are promising for wide detection applications. However, current sensing strategies mainly rely on electrochemical active analytes because of the lack of signal conversion and amplification methods. Herein, a novel histidine (His) sensor was designed based on MMIP particle and metal coordination of Cu2+ with His and cysteine (Cys). The whole determination processes were separated into recognition, coordination and detection steps. The target His in complicated samples can be selectively captured by the MMIP particles to ensure the specificity, then coordinated with Cu2+ and detected at magnetic electrodes under a specific condition to avoid contamination. Highly chemically stable MMIP particles can be prepared by the sol-gel method in large quantities at a very low cost. Additionally, the signal of Cu2+ can be significantly amplified using Cys modified Au nanoparticles. The optimized detection conditions were investigated by voltammetry. The sensor allowed His determination in a wide concentration range over 5-orders of magnitude with a low detection limit of 0.01 μM, which also expressed a promising performance in spiked water and serum samples. Accordingly, the proposed sensing strategy is beneficial for the design and preparation of novel MMIP particle-based electrochemical sensors. [Display omitted] • A novel His sensor was designed base on magnetic molecularly imprinted particle. • A promising signal amplification strategy was proposed with Cu2+ coordination. • The sensor showed a wide concentration range and low detection limit to His. • The excellent performance of the method decides its great application potential. [ABSTRACT FROM AUTHOR]

The increase of antimicrobial resistance and the outbreak of new diseases have brought unprecedented challenges with antibiotic therapy, and discovering and developing effective compounds to fight against infections or diseases have become a challenge. Conventionally, natural antibiotics or active compounds can be obtained from microorganisms with a long time span, complex screening, and cumbersome operations. In this work, we developed a droplet-based microfluidic platform combined with liquid chromatography tandem mass spectrometry for rapid screening of chemically induced mutant strains and analyzing their metabolites. Using this microfluidic method, N-methyl-N-nitro-N-nitrosoguanidine-induced mutants of two Streptomyces strains, two Salinicoccus strains, a Halomonas strain, and a Planomicrobium strain were screened, and their metabolites were analyzed. Multivariate and heatmap analysis showed that the mutant strains screened by the microfluidic method and traditional method (flasks and agar plates) were clustered and separated evidently from the wild-type strains. The top 20 differential characteristic peaks of all samples were annotated with the HMDB database, and the significant differences of the characteristic peaks indicated that the mutant strains screened by the microfluidic method and traditional method had highly similar metabolic compositions. Results demonstrated that this microfluidic screening method was suitable not only for actinomycete mutant screening, but also for bacterial mutant screening with wide applicability and reliability. Furthermore, this method can reduce screening timescales and simplify cumbersome operations compared with the traditional screening method. [Display omitted] A droplet-based microfluidic platform combined with HPLC-MS/MS was developed for screening chemically induced mutant strains and analyzing their metabolites. • A microfluidic platform was developed for screening chemically induced mutant strains. • The microfluidic platform achieved rapid screening of microbial mutant strains in 4 h. • This method was suitable not only for actinomycete mutant screening, but also for bacterial mutant screening. [ABSTRACT FROM AUTHOR]

• The novel selenol detection-based gold nanosensor was developed with high selectivity and low detection limit (11.36 nM). • The sensor was used to identify Escherichia coli by sensing selenol. • This sensor also exhibited brilliant antibacterial ability to Escherichia coli. • It was further utilized in foodstuff for Escherichia coli detection and analysis initially. A promising gold nanorod sensor that demonstrated comparable antibacterial ability, selectively recognized Escherichia coli (E. coli), and used selenol as the recognition group was prepared and applied for foodstuff E.coli detection. We used a sulfhydryl compound linked with fluorescent dye by sulfamide bonds (SH-NB) to modify gold nanorods (GNRs) and fabricate GNRs-SH-NB that can selectively and sensitively detect selenol. Selenol group broke sulfamide bonds, causing the fluorescent dye to fall off from GNRs-SH-NB and exhibit red fluorescence, demonstrating that it can selectively identify E. coli with the unique selenoenzymes or selenoproteins in the bacterium. After the decomposition of GNRs-SH-NB , the obtained GNRs modified by N-heterocyclic sulfhydryl compounds and positively charged fluorescent dyes showed synergistic antibacterial properties. Furthermore, the photothermal effect of GNRs increased the temperature beyond the optimum temperature of E. coli and caused its maladjustment, leading to the death of the bacterium. Thus, GNRs-SH-NB exerted a considerable antibacterial effect against E. coli and accurately detected E. coli in milk, meat, and eggshell. With the low limit of detection, this novel antibacterial sensor GNRs-SH-NB provide a promising method to identify the E. coli and further utilized in food safety field initially. [ABSTRACT FROM AUTHOR]