Enzymatic Catalysis in Size and Volume Dual-Confined Space of Integrated Nanochannel-Electrodes Chip for Enhanced Impedance Detection of Salmonella.

Nanochannel-based confinement effect is a fascinating signal transduction strategy for high-performance sensing, but only size confinement is focused on while other confinement effects are unexplored. Here, a highly integrated nanochannel-electrodes chip (INEC) is created and a size/volume-dual-confinement enzyme catalysis model for rapid and sensitive bacteria detection is developed. The INEC, by directly sandwiching a nanochannel chip (60 µm in thickness) in nanoporous gold layers, creates a micro-droplet-based confinement electrochemical cell (CEC). The size confinement of nanochannel promotes the urease catalysis efficiency to generate more ions, while the volume confinement of CEC significantly enriches ions by restricting diffusion. As a result, the INEC-based dual-confinement effects benefit a synergetic enhancement of the catalytic signal. A 11-times ion-strength-based impedance response is obtained within just 1 min when compared to the relevant open system. Combining this novel nanoconfinement effects with nanofiltration of INEC, a separation/signal amplification-integrated sensing strategy is further developed for Salmonella typhimurium detection. The biosensor realizes facile, rapid (<20 min), and specific signal readout with a detection limit of 9 CFU mL-1 in culturing solution, superior to most reports. This work may create a new paradigm for studying nanoconfined processes and contribute a new signal transduction technique for trace analysis application.

A Low-Field Magnetic Resonance Imaging Aptasensor for the Rapid and Visual Sensing of Pseudomonas aeruginosa in Food, Juice, and Water.

In this work, we present a low-field magnetic resonance imaging (LF-MRI) aptasensor based on the difference in magnetic behavior of two magnetic nanoparticles with diameters of 10 (MN10) and 400 nm (MN400) for the rapid detection of Pseudomonas aeruginosa (P. aeruginosa). First, specific anti-P. aeruginosa aptamers were covalently immobilized onto magnetic nanoparticles via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide chemistry for the capture of the target bacteria. In the presence of P. aeruginosa, an MN10-bacteria-MN400 (MBM) complex was formed after binding between the aptamers on magnetic nanoparticles and P. aeruginosa cells. When a magnetic field was applied, the MBM complex and free MN400 were rapidly magnetically separated, and free MN10 left in the solution worked as a T2 (transverse relaxation time) single readout in MRI measurement. Under optimum conditions, the LF-MRI platform provides both image analysis and quantitative detection of P. aeruginosa, with a detection limit of 100 cfu/mL. The feasibility and specificity of the aptasensor were demonstrated in detecting real food, orange juice, and drinking water samples and validated using plate counting methods.

Nanoconfinement Effect for Signal Amplification in Electrochemical Analysis and Sensing.

Owing to the urgent need for electrochemical analysis and sensing of trace target molecules in various fields such as medical diagnosis, agriculture and food safety, and environmental monitoring, signal amplification is key to promoting analysis and sensing performance. The nanoconfinement effect, derived from nanoconfined spaces and interfaces with sizes approaching those of target molecules, has witnessed rapid development for ultra-sensitive analyzing and sensing. In this review, the two main types of nanoconfinement systems - confined nanochannels and planes - are assessed and recent progress is highlighted. The merits of each nanoconfinement system, the nanoconfinement effect mechanisms, and applications for electrochemical analysis and sensing are summarized and discussed. This review aims to help deepen the understanding of nanoconfinement devices and their effects in order to develop new analysis and sensing applications for researchers in various fields.

Visual and quantitative detection of E. coli O157:H7 by coupling immunomagnetic separation and quantum dot-based paper strip.

Simple and visual quantitative detection of foodborne pathogens can effectively reduce the outbreaks of foodborne diseases. Herein, we developed a simple and sensitive quantum dot (QD)-based paper device for visual and quantitative detection of Escherichia coli (E. coli) O157:H7 based on immunomagnetic separation and nanoparticle dissolution-triggered signal amplification. In this study, E. coli O157:H7 was magnetically separated and labeled with silver nanoparticles (AgNPs), and the AgNP labels can be converted into millions of Ag ions, which subsequently quench the fluorescence of QDs in the paper strip, which along with the readout can be visualized and quantified by the change in length of fluorescent quenched band. Owing to the high capture efficiency and effective signal amplification, as low as 500 cfu mL-1 of E. coli O157:H7 could be easily detected by naked eyes. Furthermore, this novel platform was successfully applied to detect E. coli O157:H7 in spiked milk samples with good accuracy, indicating its potential in the detection of foodborne pathogens in real samples.

Cooperation Mode of Outer Surface and Inner Space of Nanochannel: Separation-Detection System Based on Integrated Nanochannel Electrode for Rapid and Facile Detection of Salmonella.

Nanochannels hold great prospects in intelligent systems; however, current research focuses on the inner space of the nanochannel while the outer surface is rarely explored. Here, we report on a cooperation mode of the outer surface and inner space of the nanochannel using an integrated nanochannel-electrode (INCE) and its application as a separation-detection system for rapid and facile detection of foodborne bacteria. Unlike conventional nanochannel systems, the INCE integrates two electrodes as a sensitive electrochemical interface and the nanochannel itself as nanofilter, generating a novel separation-detection system. The system is examined in a biosensing strategy based on magnetic nanoparticles (MNPs). Salmonella typhimurium (St) is taken as the target due to its severe threat to human health and food safety. By electrochemically probing the MNPs-St complex themselves on the surface of INCE, this method eliminates the requirement on additional signal labels. The biosensor presents a linear detection range from 102 to 107 CFU mL-1 and a limit of detection of 50 CFU mL-1, being comparable or even better than those of analogues with complicated signal amplification designs. Moreover, the biosensor exhibits good specificity against four types of interfering bacteria. This concept may bring new insight into the development of nanochannel research and contribute a new way to the fields of separation and detection.

Correction to: Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide.

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian blue (type Fe3O4@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe3O4 (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNP@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H2O2; (b) in an amperometric assay for H2O2; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H2O2 (at a potential as low as 50 mV) is 1.1 µM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNP@Au-PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian blue (type MNP@Au-PB). The nanocomposites worded well as candidates to develop colorimetric and electrochemical sensors of H2O2 with superior performance to analogues.

Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide.

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian Blue (type Fe3O4@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe3O4 (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNPs@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H2O2; (b) in an amperometric assay for H2O2; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H2O2 (at a potential as low as 50 mV) is 1.1 µM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNPs@PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian Blue (type MNP@Au-PB). The nanocomposites work well as candidates to develop colorimetric and electrochemical sensors of H2O2 with superior performance to analogues.

Electrochemical Conversion of Fe3O4 Magnetic Nanoparticles to Electroactive Prussian Blue Analogues for Self-Sacrificial Label Biosensing of Avian Influenza Virus H5N1.

A serious impetus always exists to exploit new methods to enrich the prospect of nanomaterials. Here, we report electrochemical conversion (ECC) of magnetic nanoparticles (MNPs) to electroactive Prussian blue (PB) analogues accompanied by three interfacial effects and its exploitation for novel label self-sacrificial biosensing of avian influenza virus H5N1. The ECC method involves a high-potential step to create strong acidic condition by splitting H2O to release Fe3+ from the MNPs, and then a low-potential step leading to the reduction of coexisting K3Fe(CN)6 and Fe3+ to K4Fe(CN)6 and Fe2+, respectively, which react to form PB analogues. Unlike conventional solid/liquid electrochemical interfaces that need a supply of reactants by transportation from bulk solution and require additional template to generate porosity, the proposed method introduces MNPs on the electrode surface and makes them natural nanotemplates and nanoconfined sources of reactants. Therefore, the method presents interesting surface templating, generation-confinement, and refreshing effects/modes, which benefit the produced PB with higher porosity and electrochemical activity, and 3 orders of magnitude lower requirement for reactant concentration compared with conventional methods. Based on the ECC methods, a sandwich immunosensor is designed for rapid detection of avian influenza virus H5N1 using MNPs as self-sacrificial labels to produce PB for signal amplification. Taking full advantages of the high abundance of Fe in MNPs and three surface effects, the ECC method endows the biosensing technology with high sensitivity and a limit of detection down to 0.0022 hemagglutination units, which is better than those of most reported analogues. The ECC method may lead to a new direction for application of nanomaterials and new electrochemistry modes.

Colorimetric Sensor Array for Thiols Discrimination Based on Urease-Metal Ion Pairs.

Thiols play a crucial role in various physiological functions, and the discrimination of thiols is a significant but difficult issue. Herein, we presented a new strategy for strengthening the discrimination of thiols by a facile colorimetric sensor array composed of a series of urease-metal ion pairs. The proposed sensor array was fabricated based on the interactions between thiols and metal ions and the effective activation of urease by thiols. Different thiols exhibited different affinities toward the metal ions, producing differential retentions of urease activity and generating distinct colorimetric response patterns. These response patterns are characteristic for each thiol and can be quantitatively differentiated by linear discriminant analysis (LDA). Cysteine (Cys), glutathione (GSH), and four other kinds of thiols have been well distinguished on the basis of this sensor array at a low concentration (1.0 µM). Remarkably, the practicability of the proposed sensor array was further validated by high accuracy (96.67%) identification of 30 unknown thiol samples. In this strategy, urease and its metal ion inhibitors were adapted to fabricate the sensor array, offering a facile way to develop sensitive array sensing systems based on inexpensive and commercially available enzymes and their inhibitors.

A colorimetric detection of acrylamide in potato chips based on nucleophile-initiated thiol-ene Michael addition.

Acrylamide (AA), a neurotoxin and a potential carcinogen, has been found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple, cost-effective, and sensitive methods for the rapid detection of AA are needed to ensure food safety. Herein, a novel colorimetric method was proposed for the visual detection of AA based on a nucleophile-initiated thiol-ene Michael addition reaction. Gold nanoparticles (AuNPs) were aggregated by glutathione (GSH) because of a ligand-replacement, accompanied by a color change from red to purple. In the presence of AA, after the thiol-ene Michael addition reaction between GSH and AA with the catalysis of a nucleophile, the sulfhydryl group of GSH was consumed by AA, which hindered the subsequent ligand-replacement and the aggregation of AuNPs. Therefore, the concentration of AA could be determined by the visible color change caused by dispersion/aggregation of AuNPs. This new method showed high sensitivity with a linear range from 0.1 µmol L(-1) to 80 µmol L(-1) and a detection limit of 28.6 nmol L(-1), and especially revealed better selectivity than the fluorescence sensing method reported previously. Moreover, this new method was used to detect AA in potato chips with a satisfactory result in comparison with the standard methods based on chromatography, which indicated that the colorimetric method can be expanded for the rapid detection of AA in thermally processed foods.

Electrochemical Impedance Immunosensor Based on Self-Assembled Monolayers for Rapid Detection of Escherichia coli O157:H7 with Signal Amplification Using Lectin.

Escherichia coli O157:H7 is a predominant foodborne pathogen with severe pathogenicity, leading to increasing attention given to rapid and sensitive detection. Herein, we propose an impedance biosensor using new kinds of screen-printed interdigitated microelectrodes (SPIMs) and wheat germ agglutinin (WGA) for signal amplification to detect E. coli O157:H7 with high sensitivity and time-efficiency. The SPIMs integrate the high sensitivity and short response time of the interdigitated electrodes and the low cost of the screen-printed electrodes. Self-assembling of bi-functional 3-dithiobis-(sulfosuccinimidyl-propionate) (DTSP) on the SPIMs was investigated and was proved to be able to improve adsorption quantity and stability of biomaterials. WGA was further adopted to enhance the signal taking advantage of the abundant lectin-binding sites on the bacteria surface. The immunosensor exhibited a detection limit of 102 cfu·mL(-1), with a linear detection range from 10(2) to 10(7) cfu·mL(-1) (r2 = 0.98). The total detection time was less than 1 h, showing its comparable sensitivity and rapid response. Furthermore, the low cost of one SPIM significantly reduced the detection cost of the biosensor. The biosensor may have great promise in food safety analysis and lead to a portable biosensing system for routine monitoring of foodborne pathogens.

Exploiting enzyme catalysis in ultra-low ion strength media for impedance biosensing of avian influenza virus using a bare interdigitated electrode.

Enzyme catalysis is broadly used in various fields but generally applied in media with high ion strength. Here, we propose the exploitation of enzymatic catalysis in ultra-low ion strength media to induce ion strength increase for developing a novel impedance biosensing method. Avian influenza virus H5N1, a serious worldwide threat to poultry and human health, was adopted as the analyte. Magnetic beads were modified with H5N1-specific aptamer to capture the H5N1 virus. This was followed by binding concanavalin A (ConA), glucose oxidase (GOx), and Au nanoparticles (AuNPs) to create bionanocomposites through a ConA-glycan interaction. The yielded sandwich complex was transferred to a glucose solution to trigger an enzymatic reaction to produce gluconic acid, which ionized to increase the ion strength of the solution, thus decreasing the impedance on a screen-printed interdigitated array electrode. This method took advantages of the high efficiency of enzymatic catalysis and the high susceptibility of electrochemical impedance on the ion strength and endowed the biosensor with high sensitivity and a detection limit of 8 × 10(-4) HAU in 200 µL sample, which was magnitudes lower than that of some analogues based on biosensing methods. Furthermore, the proposed method required only a bare electrode for measurements of ion strength change and had negligible change on the surficial properties of the electrode, though some modification of magnetic beads/Au nanoparticles and the construction of a sandwich complex were still needed. This helped to avoid the drawbacks of commonly used electrode immobilization methods. The merit for this method makes it highly useful and promising for applications. The proposed method may create new possibilities in the broad and well-developed enzymatic catalysis fields and find applications in developing sensitive, rapid, low-cost, and easy-to-operate biosensing and biocatalysis devices.

Filling carbon nanotubes with Prussian blue nanoparticles of high peroxidase-like catalytic activity for colorimetric chemo- and biosensing.

Facile filling of multiwalled carbon nanotubes (MWCNTs) with Prussian blue nanoparticles (PBNPs) of high peroxidase-like catalytic activity was performed to develop novel colorimetric sensing protocols for assaying H2O2 and glucose. Fine control of PBNP growth was achieved by modulating the concentration ratio of K3 [Fe(CN)6] and FeSO4 precursors in an acidic solution containing ultrasonically dispersed MWCNTs, and thus size-matched PBNPs could be robustly immobilized in the cavities of the MWCNTs (MWCNT-PBin). Unlike other reported methods involving complicated procedures and rigorous preparation/separation conditions, this mild one-pot filling method has advantages of easy isolation of final products by centrifugation, good retention of the pristine outer surface of the MWCNT shell, and satisfactory filling yield of (24±2) %. In particular, encapsulation of PBNPs of poor dispersibility and limited functionality in dispersible and multifunctional MWCNT shells creates new and valuable opportunities for quasihomogeneous-phase applications of PB in liquid solutions. The MWCNT-PBin nanocomposites were exploited as a peroxidase mimic for the colorimetric assay of H2O2 in solution by using 3,3',5,5'-tetramethylbenzidine (TMB) as reporter, and they gave a linear absorbance response from 1 µM to 1.5 mM with a limit of detection (LOD) of 100 nM. Moreover, glucose oxidase (GOx) was anchored on the outer surface of MWCNT-PBin to form GOx/MWCNT-PBin bionanocomposites. The cooperation of outer-surface biocatalysis with peroxidase-like catalysis of interior PB resulted in a novel cooperative colorimetric biosensing mode for glucose assay. The use of GOx/MWCNT-PBin for colorimetric biosensing of glucose gave a linear absorbance response from 1 µM to 1.0 mM and an LOD of 200 nM. The presented protocols may be extended to other multifunctional nanocomposite systems for broad applications in catalysis and biotechnology.

Microwave-Enabled Fast Preparation of a Metal-Organic Framework Hybrid Membrane for Filtration-Enhanced Simultaneous Separation and Detection of Aflatoxin B1.

Mycotoxin contamination in food and the environment seriously harms human health. Sensitive and timely detection of mycotoxins is crucial. Here, we report a dual-functional hybrid membrane with absorptivity and responsiveness for fluorescent-quantitative detection of mycotoxin aflatoxin B1 (AFB1). A biomineralization-inspired and microwave-accelerated fabrication method was established to prepare a hybrid membrane with a metal-organic framework (MOF) loaded in high density. The MOF presented high efficiency in capturing AFB1 and showed fluorescence intensity alteration simultaneously, enabling a dual adsorption-response mode. Deriving from the inherent porous structure of the hybrid membrane and the absorptive/responsive ability of the loaded MOF, a filtration-enhanced detection mode was elaborated to provide a 1.67-fold signal increase compared with the conventional soaking method. Therefore, the hybrid membrane exhibited a rapid response time of 10 min and a low detection limit of 0.757 ng mL-1, superior to most analogues in rapidity and sensitivity. The hybrid membrane also presented superior specificity, reproducibility, and anti-interference ability and even performed well in extreme environments such as strong acid or alkaline, satisfying the practical requirements for facile and in-field detection. Therefore, the membrane had strong applicability in chicken feed samples, with a detection recovery between 70.6% and 101%. The hybrid membrane should have significant prospects in the rapid and in-field inspection of mycotoxins for agriculture and food.

Thiol-ene chemistry guided preparation of thiolated polymeric nanocomposite for anodic stripping voltammetric analysis of Cd2+ and Pb2+.

We report on the thiol-ene chemistry guided preparation of a novel thiolated polymeric nanocomposite involving polyaniline (PANI), a functionalized thiol, e.g., sulfur-rich 2,5-dimercapto-1,3,4-thiadiazole (DMcT), and multiwalled carbon nanotubes (MWCNTs) for the sensitive differential pulse anodic stripping voltammetric determination of Cd(2+) and Pb(2+) on a glassy carbon electrode (GCE). Briefly, the thiol-ene reaction of a thiol with oxidized PANI that was chemically synthesized in the presence of solution-dispersed acidified MWCNTs yielded a thiolated polymeric nanocomposite of thiol-PANI/MWCNTs. The thiols examined include DMcT, 1,6-hexanedithiol and ß-mercaptoethanol. Quartz crystal microbalance, cyclic voltammetry, scanning electron microscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were used for film characterization and process monitoring. Under the optimized conditions, the obtained Bi/Nafion/DMcT-PANI/MWCNTs/GCE can sensitively sense Cd(2+) and Pb(2+) with limits of detection of 0.01 and 0.04 µg L(-1), respectively.

Recent advances in determination applications of emerging films based on nanomaterials.

Sensitive and facile detection of analytes is crucial in various fields such as agriculture production, food safety, clinical diagnosis and therapy, and environmental monitoring. However, the synergy of complicated sample pretreatment and detection is an urgent challenge. By integrating the inherent porosity, processability and flexibility of films and the diversified merits of nanomaterials, nanomaterial-based films have evolved as preferred candidates to meet the above challenge. Recent years have witnessed the flourishment of films-based detection technologies due to their unique porous structures and integrated physical/chemical merits, which favors the separation/collection and detection of analytes in a rapid, efficient and facile way. In particular, films based on nanomaterials consisting of 0D metal-organic framework particles, 1D nanofibers and carbon nanotubes, and 2D graphene and analogs have drawn increasing attention due to incorporating new properties from nanomaterials. This paper summarizes the progress of the fabrication of emerging films based on nanomaterials and their detection applications in recent five years, focusing on typical electrochemical and optical methods. Some new interesting applications, such as point-of-care testing, wearable devices and detection chips, are proposed and emphasized. This review will provide insights into the integration and processability of films based on nanomaterials, thus stimulate further contributions towards films based on nanomaterials for high-performance analytical-chemistry-related applications.

Metal-Organic Framework-Decorated Nanochannel Electrode: Integration of Internal Nanoconfined Space and Outer Surface for Small-Molecule Sensing.

Ionic current measurement has been the dominant signaling strategy in nanochannel-based sensors. However, the direct probing of the capture of small molecules is still challenging, and the sensing potential of the outer surface of nanochannels is always ignored. Here, we report the fabrication of an integrated nanochannel electrode (INCE) with nanoporous gold layers modified on two sides of nanochannels, and its application for small-molecule analysis was explored. Metal-organic frameworks (MOFs) were decorated inside and outside of nanochannels, enabling the reduction of pore size to several nanometers, which is among the thickness range of the electric double layer for confined ion diffusion. Combined with excellent adsorption characteristics of MOFs, the developed nanochannel sensor successfully constructed the internal nanoconfined space that could directly capture small molecules and instantly generate a current signal. The contribution of the outer surface and the internal nanoconfined space to diffusion suppression to electrochemical probes was investigated. We found that the constructed nanoelectrochemical cell was sensitive in both the inner channel and the outer surface, signifying a novel sensing mode with integration of the internal nanoconfined space and the outer surface of nanochannels. The MOF/INCE sensor showed excellent performance toward tetracycline (TC) with a detection limit of 0.1 ng·mL-1. Subsequently, sensitive and quantitative detection of TC down to 0.5 µg·kg-1 was achieved in actual chicken samples. This work may open up a new model of nanoelectrochemistry and provide an alternative solution in the field of nanopore analysis for small molecules.

Blood-Coagulation-Inspired Dynamic Bridging Strategy for the Fabrication of Multiscale-Assembled Hierarchical Porous Material.

Porous materials, from macroscopic bulk materials (MBs) with (sub-)millimeter-scale pores to tiny particles (TPs) with (sub-)nanometer-scale pores, have attracted ever-growing interest in various fields. However, the integration of multi-scale pores in one composite is promising but challenging, owing to the considerable gap in the scale of the pores. Inspired by blood coagulation, a fibrin-based dynamic bridging strategy is developed to fabricate a multiscale-assembled hierarchical porous material (MHPM), in which fibrin formed as the sub-framework for the weaving-narrow of MBs and the enwinding-load of TPs. The bio-polymerization nature makes the fabrication rapid, facile, and universal for the customizable integration of seven kinds of TPs and four kinds of MBs. Besides, the integration is controllable with high load capacity of TPs and is stable against external shock forces. The unique multi-level structure endows the MHPM with large and accessible surface area, and efficient mass transfer pathways, synergistically leading to high adsorption capacity and rapid kinetics in multiple adsorption models. This work suggests a strategy for the rational multi-level design and fabrication of hierarchical porous architectures.

Nanoconfined MXene-MOF Nanolaminate Film for Molecular Removal/Collection and Multiple Sieving.

Balancing the trade-off between permeability and selectivity while realizing multiple sieving from complex matrices remains as bottlenecks for membrane-based separation. Here, a unique nanolaminate film of transition metal carbide (MXene) nanosheets intercalated by metal-organic framework (MOF) nanoparticles was developed. The intercalation of MOFs modulated the interlayer spacing and created nanochannels between MXene nanosheets, promoting a fast water permeance of 231 L m-2 h-1 bar-1. The nanochannel endowed a 10-fold lengthened diffusion path and the nanoconfinement effect to enhance the collision probability, establishing an adsorption model with a separation performance above 99% to chemicals and nanoparticles. In addition to the remained rejection function of nanosheets, the film integrated dual separation mechanisms of both size exclusion and selective adsorption, enabling a rapid and selective liquid phase separation paradigm that performs simultaneous multiple chemicals and nanoparticles sieving. The unique MXenes-MOF nanolaminate film and multiple sieving concepts are expected to pave a promising way toward highly efficient membranes and additional water treatment applications.

Rapid detection of multiple antibiotics in chicken samples via a fluorescence nanobiosensor coupled with a homemade fluorescence analyzer.

Antibiotic residues in foods pose a serious threat to human health. However, routine analysis techniques require bulky laboratory instruments and skilled personnel or give single-channel analysis results, exhibiting low practicality. Here, we explored a rapid and easy-to-use detection system combining a fluorescence nanobiosensor with a homemade fluorescence analyzer for the simultaneous identification and quantification of multiple antibiotics. The nanobiosensor assay worked based on the targeted antibiotics competing with signal labels of antigen-quantum dots (IQDs) to bind with recognition elements of antibody-magnetic beads (IMBs). The fluorescence signals of IMB-unbound IQDs in a magnetically separated supernatant, related to antibiotic concentration, were automatically collected and processed by our self-designed and homemade fluorescence analyzer which integrated mechanical control hardware (consisting of a mechanical arm, a ten-channel rotary bench, and an optical detection unit) and user control software (installed on a built-in laptop). The fluorescence analyzer enabled the analysis of 10 samples within 5 min in one round and permitted the real-time uploading of sample data to the cloud. By employing three QDs with emission wavelengths of 525 nm, 575 nm, and 625 nm, this multiplex fluorescence biosensing system demonstrated great sensitivity and accuracy for simultaneously analyzing enrofloxacin, tilmicosin, and florfenicol in chicken samples with detection limits of 0.34 µg kg-1, 0.7 µg kg-1, and 0.16 µg kg-1, respectively. Moreover, the biosensing platform performed well in a wealth of chicken samples covering various breeds from three Chinese cities. This study identifies a generic and user-friendly multiplex biosensor platform with significant potential for use in food safety and regulation.