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.

Sub-second ultrafast yet programmable wet-chemical synthesis.

Wet-chemical synthesis via heating bulk solution is powerful to obtain nanomaterials. However, it still suffers from limited reaction rate, controllability, and massive consumption of energy/reactants, particularly for the synthesis on specific substrates. Herein, we present an innovative wet-interfacial Joule heating (WIJH) approach to synthesize various nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. In the WIJH, Joule heat generated by the graphene film (GF) is confined at the substrate-solution interface. Accompanied by instantaneous evaporation of the solvent, the temperature is steeply improved and the precursors are concentrated, thereby synergistically accelerating and controlling the nucleation and growth of nanomaterials on the substrate. WIJH leads to a record high crystallization rate of HKUST-1 (~1.97 µm s-1), an ultralow energy cost (9.55 × 10-6 kWh cm-2) and low precursor concentrations, which are up to 5 orders of magnitude faster, -6 and -2 orders of magnitude lower than traditional methods, respectively. Moreover, WIJH could handily customize the products' amount, size, and morphology via programming the electrified procedures. The as-prepared HKUST-1/GF enables the Joule-heating-controllable and low-energy-required capture and liberation towards CO2. This study opens up a new methodology towards the superefficient synthesis of nanomaterials and solvent-involved Joule heating.

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.

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.

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.

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.

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.

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.

Portable and durable sensor based on porous MOFs hybrid sponge for fluorescent-visual detection of organophosphorus pesticide.

Pesticide residues have raised serious public concern towards agriculture, environment and food safety. Recently, metal-organic frameworks (MOFs) have been employed as promising recognition and signal generation elements in sensors for pesticide detection. However, the general format of tiny particles with poor dispersity brings obstacles to detection operation and the improvement of sensing performance. Here, we report a sensor based on porous MOFs hybrid sponge for fluorescent-visible detection of methyl parathion. Benefiting from the intermediate of adhesive and porous fibrin film, MOFs are loaded with good dispersion and accessibility, thereby endowing the sensor with a rapid response time of 10-min, a wide linear detection range of 50-2500 µg L-1, and a low limit of detection of 4.95 µg L-1. Moreover, the hybrid sensor presented superior durability and anti-interference ability to the detection in complex conditions, including organic solvents, acidic solution, high temperature, and even chemical interferences. This hybrid not only provides a new construction strategy for a nanomaterial-based sensor, but also permits a portable and durable route for the detection.

Study on the mechanism of the black crust formation on the ancient marble sculptures and the effect of pollution in Beijing area.

In Beijing area, the precious stone objects often suffer from the black crusts on the specific parts of the objects, in order to understand the forming mechanism of the black crusts, samples from the stone sculptures in Beijing Stone Carving Art Museum, ZHIHUA Temple and Museum of Western Zhou Yandu Relics were taken and studied. Nondestructive measurement was carried out firstly to acquire main elements of the samples by portable X-ray spectrum (pXRF). Morphology and microstructure of typical black crust samples were examined by ultra-depth of field microscope (UDFM) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Compositions of black crusts and body rocks were evaluated with X-ray diffraction (XRD), Raman spectra and mapping. Inductively coupled plasma optical emission spectrometry (ICP-OES) and pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) were used to identify the major pollution sources leading to the black crusts. Through this study, the composition of the black crusts was revealed. Different gypsum crystals and carbonaceous species were found. Pollutant elements analysis and pyrolysis products provide indicators of the pollution sources. As consequence of strong photochemical oxidation processes and the high temperature from June to September in Beijing, more acid rain precursors can be formed. Frequent sulphation process occurs on the CaCO3/CaMg(CO3)2 surface. Combining morphology results and atmospheric data, the formation of black crusts in Beijing can be deduced.

Chemical and electrochemical conversion of magnetic nanoparticles to Prussian blue for label-free and refreshment-enhanced electrochemical biosensing of enrofloxacin.

Magnetic biosensor takes advantage of rapid and facile magnetic separation/collection of targets, however, generally relies on additional signal labels to generate signal in a tedious and high-cost way. Here, we proposed a chemical and electrochemical conversion (C-ECC) method to develop a label-free electrochemical magnetic biosensor to detect antibiotics enrofloxacin (ENR). The C-ECC method integrates the chemical decomposition of magnetic beads (MBs) to release ironic ions and the simultaneous electrochemical deposition of Prussian blue (PB) analogs through the reaction of ironic ions and co-existing K4Fe(CN)6. Unlike conventional method that relies on the physical magnetic property of MBs, the C-ECC method fully exploited the chemical/electrochemical properties of MBs to produce electrochemically active PB to generate signal, thus endowing MBs with dual roles in both sample treatment and signal generation. The incorporation of chemical and electrochemical conversion produced more PB with higher electroactivity when compared with sole chemical or electrochemical conversion. Moreover, an interesting electrochemical refreshment (ER) was designed to remove insulative species on the electrode surface to improve electroactivity of electrode and benefit amperometric detection significantly. Under optimized conditions, the C-ECC-based biosensor presented limit of detection (LOD) of 4.17 pg mL-1 for ENR, which is lower than most analogs, as well as satisfactory specificity. The biosensor also performed well in fish and chicken meat samples, with LODs lower than maximum residue limits of national standards. The C-ECC method may create a new way to design magnetic sensors and contribute to rapid, facile and sensitive detection in agriculture/food, clinic diagnosis and environmental monitoring.

A High-Performance MEMS Accelerometer with an Improved TGV Process of Low Cost.

High-performance MEMS accelerometers usually use a pendulum structure with a larger mass. Although the performance of the device is guaranteed, the manufacturing cost is high. This paper proposes a method of fabricating high-performance MEMS accelerometers with a TGV process, which can reduce the manufacturing cost and ensure the low-noise characteristics of the device. The TGV processing relies on laser drilling, the metal filling in the hole is based on the casting mold and CMP, and the packaging adopts the three-layer anodic bonding process. Moreover, for the first time, the casting mold process is introduced to the preparation of MEMS devices. In terms of structural design, the stopper uses distributed comb electrodes for overload displacement suppression, and the gas released by the packaging method provides excellent mechanical damping characteristics. The prepared accelerometer has an anti-overload capability of 10,000 g, the noise density is less than 0.001°/√Hz, and it has ultra-high performance in tilt measurement.

A CRISPR-Cas12a-powered magnetic relaxation switching biosensor for the sensitive detection of Salmonella.

Magnetic relaxation switching (MRS) biosensors are attractive in the field of food safety owing to their simplicity and high signal-to-noise ratio. But they are less in sensitivity and stability caused by the insufficient crosslinking or non-specific binding of magnetic nanoparticles (MNPs) with targets. To address this problem, the CRISPR-Cas12a system was introduced into an MRS biosensor for the first time, to precisely control the binding of two types of MNPs with sizes of 130 nm (MNP130) and 30 nm (MNP30), for the sensitive detection of Salmonella. Delicately, the biosensor was designed based on the different magnetic properties of the two sizes of MNPs. The target Salmonella activated the collateral cleavage activity of the CRISPR-Cas12a system, which inhibited the binding of the two sizes of MNPs, resulting in an increase of unbound MNP30. After separating MNP130-MNP30 complexes and MNP130 from MNP30, the free MNP30 left in solution acted as transverse relaxation time (T2) signal reporters for Salmonella detection. Under optimized conditions, the CRISPR-MRS biosensor presented a limit of detection of 1.3 × 102 CFU mL-1 for Salmonella, which is lower than most MRS biosensor analogues. It also showed satisfactory specificity and performed well in spiked chicken meat samples. This biosensing strategy not only extends the reach of the CRISPR-Cas12a system in biosensors but also offers an alternative for pathogen detection with satisfactory sensitivity.

Monovalent Antigen-Induced Aggregation (MAA) Biosensors Using Immunomagnetic Beads in Both Sample Separation and Signal Generation for Label-Free Detection of Enrofloxacin.

Exploring new functions of nanomaterials can help facilitate the development of biosensors for the detection of antibiotics. Herein, a new detection modality based on monovalent antigen-induced aggregation (MAA) of immunomagnetic beads (IMBs) was proposed for rapid and label-free detection of enrofloxacin (ENR), which endowed IMBs with the abilities of both sample separation and signal generation. In the presence of ENR, the initially well-dispersed IMBs were aggregated and the degree of aggregation was in a concentration-dependent manner. After exploring the mechanism underlying IMB aggregation and investigating the key parameters affecting it, a label-free biosensing platform was developed for rapid and sensitive detection of ENR. Based on the significant differences in the magnetic separation speed and size between the aggregated and well-dispersed IMBs, two methods were proposed for quantitatively determining ENR, i.e., measuring the turbidity of the IMB supernatant after magnetic separation for a given time and visualizing and calculating the grayscale value of the aggregated IMBs trapped on the surface of a nitrocellulose membrane. A three-dimensional (3D)-printed syringe was designed and fabricated for automatic filtration of IMBs. This immunosensor allowed for sensitive detection of ENR in less than 15 min without any labels. It exhibited a satisfactory limit of detection of 0.79 ng mL-1 and showed the feasibility for ENR detection of spiked chicken meat with recovery rates ranging from 74.8 to 98.3%. The MAA immunosensor can act as a promising tool to detect trace levels of ENR and has the potential to be applied to complex food samples.

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.

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.

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.

Efficacy and prognosis analyses of apatinib combined with S-1 in third-line chemotherapy for advanced gastric cancer.

PURPOSE: To explore the efficacy and safety of apatinib (an anti-angiogenic drug) combined with S-1 (a fluorouracil drug) in the third-line chemotherapy for advanced gastric cancer, and to analyze the factors influencing the prognosis. METHODS: Eighty-four patients with advanced gastric cancer, who did not respond to second-line or above chemotherapy and were treated in our hospital were enrolled and divided into Apatinib+S-1 group (n=42) and S-1 group (n=42), based on different treatments applied. Next, the clinical responses and adverse reactions of patients were observed and recorded. The patients were followed up through the outpatient service and telephone to record their survival and disease progression. Additionally, the factors affecting the prognosis of patients were analyzed. RESULTS: The objective response rate (ORR) and disease control rate (DCR) in the Apatinib+S-1 group were 9.5% (4/42) and 71.4% (30/42), respectively, which were significantly higher than those in the S-1 group. The main adverse reactions after therapy included neutropenia, thrombocytopenia, anemia, stomatitis, hypertension, proteinuria, hand-foot syndrome and gastrointestinal reaction, which were mostly of grade I-II. The incidence rates of hypertension, proteinuria and hand-foot syndrome were 42.9%, 26.2%, and 23.8%, respectively, in the Apatinib+S-1 group, which were overtly higher than those in the S-1 group. There was no statistically significant difference in the overall survival (OS) of patients between two groups (p=0.063), while the progression free survival (PFS) of patients was overtly longer in the Apatinib + S-1 group than that in S-1 group. Univariate analysis of PFS showed that the PFS of patients with high differentiation of tumor or post-treatment proteinuria or hand-foot syndrome was evidently higher than that of patients without high differentiation of tumor or post-treatment proteinuria or hand-foot syndrome. CONCLUSION: Patients with advanced gastric cancer achieve relatively satisfactory short-term therapeutic effects after treatment with apatinib combined with S-1 in the third-line therapy, whose PFS is notably better than those treated with S-1 alone, and they are tolerant to adverse reactions. Highly differentiated tumors and post-treatment proteinuria and hand-foot syndrome are predictable factors for the PFS of patients.

Integration and synergy in protein-nanomaterial hybrids for biosensing: Strategies and in-field detection applications.

Biosensors contribute a lot to the reliable and sensitive detection in various fields, especially emerging trends of in-field and real-time detection for point-of-care diagnosis, food safety and environmental monitoring. The signal amplification that improves the analytical performance and the compact integration of various biosensing components with/in miniaturized and portable devices are essential but still challenging. Integrating the merits of bio-active proteins (enzyme, antibody, etc.) and nanomaterials (nanoparticles, nanotubes, nanosheets, nanoflowers etc.) with abundant physicochemical properties, numerous protein-nanomaterial hybrids (PN hybrids) have been designed and applied for biosensing in recent years. PN hybrids can serve as not only sensitive probes for analyte recognition and signal generation/amplification thereby enhancing analytical performance, but also miniaturized and full-functional sensing components that are easily combined with other devices, greatly simplifying the construction and assay procedures. In this review, the state-of-art strategies of PN hybrids for biosensing are summarized from the view of the role of nanomaterial components, i.e. immobilization matrix, catalyst, and label. Recent advances for the emerging in-field detection applications of PN hybrids with the incorporation of portable hand-held readers and miniaturized devices are then surveyed. The features of PN hybrids for the construction of these miniaturized biosensors are focused. The integration and synergy between proteins and nanomaterials for biosensing is emphasized and discussed.

Understanding the changes in spatial fairness of urban greenery using time-series remote sensing images: A case study of Guangdong-Hong Kong-Macao Greater Bay.

Urban greenery is essential to the living environment of humans. Objectively assessing the rationality of the spatial distribution of green space resources will contribute to regional greening plans, thereby reducing social injustice. However, it is difficult to propose a reasonable greening policy aimed at the coordinated development of an urban agglomeration due to a lack of baseline information. This study investigated the changes in spatial fairness of the greenery surrounding residents in Guangdong-Hong Kong-Macao Greater Bay by examining time-series remote sensing images from 1997 to 2017. With the substitution of impervious, artificial surfaces for universal areas of human activities, we quantified the amount of surrounding greenery from the perspective of human activities at the pixel level by utilizing a nested buffer. The Gini coefficient was further calculated for each city to quantify the spatial fairness of the surrounding greenery to people. The results indicated that areas with less greenery surrounding them decreased during 1997 and 2017 in Guangdong-Hong Kong-Macao Greater Bay. The spatial fairness did not tend to increase with the improvements in the overall greening level. The spatial fairness of 4 cities had an increasing trend, and the Gini coefficients of 5 cities were still over 0.6 in 2017. We further proposed different greening policy suggestions for different cities based on the amount of greenery surrounding people and the trend in fairness. The results and the conclusion of this research will help to improve future regional greening policies and to reduce environmental injustice.