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Simultaneous detection of live and dead bacteria is a huge challenge for food safety. To solve this issue, an all-in-one biosensor for bacteria was developed using the phage-apoferritin@CuO 2 (phage-Apo@CP) probe on an antimicrobial peptide (AMP)/MXenes-modified detection platform. With the specific recognition of AMP and phage-Apo@CP, the biosensor for the target Escherichia coli O157:H7 (E. coli O157:H7) presented multi-mode (bioluminescent, colorimetric, and electrochemical) signals to simultaneously measure live and dead bacteria. The bioluminescent signal caused by the adenosine triphosphate (ATP) from the bacteria was used to quantify live bacteria. The colorimetric and voltammetric signals triggered by ·OH and Cu 2+ from the probe with the assistance of acid could rapidly screen and quantitative determination of total E. coli O157:H7 concentration. Thus, the dead one was obtained according to the total and live ones. All three signals could be mutually corrected to improve the accuracy. The biosensor was successfully used for on-site measurement of live and dead E. coli O157:H7 in food samples with the limit of detection of 30 CFU/mL for live ones and 6 CFU/mL for total bacteria within 50 min. This work presents a novel pathway for rapid and simultaneous quantification of both live and dead bacteria., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Presently, chemotherapy remains to be one of the most important therapeutic approaches for malignant tumors. Ligands based drug conjugates are showing considerable promise as potential therapeutic agents delivery systems for cancer. Here, a series of HSP90 inhibitors-SN38 conjugates were developed through cleavable linkers for tumor-specific delivery of SN38 and reducing its side effects. In vitro assays showed that these conjugates exhibited acceptable stability in PBS and plasma, appreciable HSP90 binding affinity, and potent cytotoxic abilities. Cellular uptake behaviors also indicated that these conjugates could selectively target cancer cells in a time-dependent manner via HSP90. Among them, compound 10b with a glycine linkage exhibits appreciable in vitro and in vivo pharmacokinetic profiles, and excellent in vivo antitumor activity in Capan-1 xenograft models, demonstrating the selective targeting and accumulation of the active payload at tumor sites. Above all, these results suggest that compound 10b has the potential as a potent anticancer drug, meriting further evaluation in the future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

D-Amino acid oxidase (DAAO) is an imperative oxidoreductase that oxidizes D-amino acids to corresponding keto acids, producing ammonia and hydrogen peroxide. Previously, based on the sequence alignment of DAAO from Glutamicibacter protophormiae (GpDAAO-1) and (GpDAAO-2), 4 residues (E115, N119, T256, T286) at the surface regions of GpDAAO-2, were subjected to site-directed mutagenesis and achieved 4 single-point mutants with enhanced catalytic efficiency (k cat /K m ) compared to parental GpDAAO-2. In the present study, to further enhance the catalytic efficiency of GpDAAO-2, a total of 11 (6 double, 4 triple, and 1 quadruple-point) mutants were prepared by the different combinations of 4 single-point mutants. All mutants and wild types were overexpressed, purified and enzymatically characterized. A triple-point mutant E115A/N119D/T286A exhibited the most significant improvement in catalytic efficiency as compared to wild-type GpDAAO-1 and GpDAAO-2. Structural modeling analysis elucidated that residue Y213 in loop region C209-Y219 might act as the active-site lid for controlling substrate access, the residue K256 substituted by threonine (K256T) might change the hydrogen bonding interaction between residue Y213 and the surrounding residues, and switch the conformation of the active-site lid from the closed state to the open state, resulting in the enhancement in substrate accessibility and catalytic efficiency., Competing Interests: Conflict of interest The authors declare no conflict of interest regarding the data presented in the manuscript., (Copyright © 2023 Elsevier Inc. All rights reserved.)

It was critically important to develop some sensitive, rapid, and specific imaging or detection methods for the virulent strain in food safety monitoring. In the study, a novel tetraphenyl mono-phenylboronic acid dye (TPE-PBA) with good aggregation-induced emission (AIE) features and high combining capacity towards bacteria was first synthesized. With TPE-PBA as a signal tag, a sandwich-type AIE probe-linked phage sorbent assay was developed for imaging and detecting virulent strains using Escherichia coli O157:H7 (E. coli O157:H7) as a representative. In the assay, phages for E. coli O157:H7 were firstly fixed on the bottom of a 96-well plate to specifically capture the strain, then the TPE-PBA signal tag was added and incubated with the captured strain to produce the phage/E. coli O157:H7/TPE-PBA complex. The complex could produce intensive AIE fluorescence being proportional to the amount of E. coli O157:H7 with a detection limit of 30 CFU mL -1 within 30 min. Simultaneously, the strain could be imaged in the plate with good anti-photobleaching and AIE effects. The results demonstrated the AIE-linked phage sorbent assay with a TPE-PBA signal tag could provide a suitable platform for rapid and specific detection and imaging of virulent strains. Therefore, it exhibited good application prospects in the on-site monitoring of food pathogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

It is crucially important to develop simple, selective, and rapid extraction pretreatments and analytical methods to detect microcystins (MCs) in food samples with complex matrices. In this study, a magnetic self-assembled covalent organic framework (COF) adsorbent was synthesized via a facile approach by using a one-pot reaction of 1,6-bis(4-formylphenyl)-3,8-bis(4-aminophenyl)pyrene (BFBAPy) as precursors to assemble amino-functionalized magnetic Fe 3 O 4 -NH 2 nanoparticles (Fe 3 O 4 @Py-COF, simplified as mCOF). The superparamagnetic mCOF is found to exhibit a high specific surface area, abundant nanopores and good stability. In particular, adsorption experiments demonstrate that mCOF exhibits a good adsorption capability, efficiency and some specificity to MCs. The mCOF was applied for magnetic solid phase extraction (MSPE) of two kinds of MCs (MC-LR and MC-RR) from aquatic samples followed by high-performance liquid chromatography-diode array detection (HPLC-DAD). Under the optimized conditions, good linearity is obtained in the range of 10-1000 µg/kg (R 2 ≥0.9989), the limits of detection are 3.0-4.5 µg/kg, and the relative standard deviations (RSDs) are lower than 4.9% (n=5). The extraction recoveries are also satisfactory (84.2%-105%). These results demonstrate that the developed method can be used as a good alternative method for the selective determination of MCs in complex aquatic foods., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

In this work, a disposable and inexpensive bamboo stir bar containing an organic membrane was constructed to perform stir bar sorptive extraction (SBSE), followed by portable mass spectrometry to achieve on-site detection of four residual drugs (malachite green, crystal violet and their metabolites) in fishes. The entire method uses only microliter quantities of organic solvents, enabling environmentally friendly pretreatment. The portable mass spectrometer can simultaneously detect four target analytes in a sample in approximately ten seconds. Under the optimal conditions, the proposed method was successfully applied to simultaneously detect four drugs in fish samples with detection limits of 0.16-0.59 µg/kg. The spiked recoveries for mandarin fish and lateolabrax maculatus were 74.5-96.5%, with relative standard deviations (RSD) of 4.4-16%. In addition, the matrix effects of the four analytical targets in the method were experimentally verified to range from 7.30% to 20.62%. The method can potentially be extended to the on-site detection of other veterinary drug residues in foods., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

It is challenging to greatly increase of the extraction selectivity and efficiency by stir bar sorptive extraction of ultra-trace polychlorinated biphenyls (PCBs) in complex environmental matrix, e.g., soils. To fulfill this purpose, one of the critical works is to prepare some coatings with high selectivity, adsorptive capacity and reusability. It is also important to develop some green, simple methods for preperation the coatings. In this work, a kind of highly efficient and bioactive coating based on hyperbranched aptamer (HB-Apt) was constructed via hybridization chain reaction (HCR). Then, the HB-Apt was coated on a magnetic stir bar and applied to headspace extraction of PCB72 and PCB106 in soils. The core-shell gold magnetic particles (Fe 3 O 4 @AuNPs, AuMNPs for short) was employed as the substrate to immobilize the HB-Apt. The extracted PCBs on the stir bar could be easily eluted in ethanol by stirring, and then sampled in gas chromatography-mass spectrometry (GC-MS) for qualification. The ultra-low detection limit (0.003-0.005 ng•g -1 ), good linearity (0.01-500 ng•g -1 , R 2 ≥0.994) and reproducibility (RSD: 4.58-6.53%) were obtained. Compared with the common aptamer coating, the HB-Apt coating exhibited good selectivity and higher extraction capacity. The results might be related to the fact that there are more aptamer fragments grated on the HB-Apt coating than those of the common aptamer coating. The magnetic stir bar can not only be employed for easy headspace extraction, but also facilitate separation and elution. Moreover, the coating could be recycled for at least 60 times before recoveries of the PCB72 and PCB106 in the spiked samples drop below 90%. All these indicated that the assay is simple, robust, environment friendly and promising for detection of trace PCBs in complex environmental samples., Competing Interests: Declaration of Competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

It's important to eliminate matrix interference for accurate detecting antibiotic residues in complex food samples. In this study, we designed a zero-backgrounded fluorescence aptasensor to achieve on-site detection of antibiotic residues, with chloramphenicol (CAP) as representative analyte. Moreover, a three stir-bars assisted target recycling system (TSBTR) was designed to achieve triple signal amplification and increase the sensitivity. The bars included one magnetic stir-bar modified with two kinds of long DNA chains, and two gold stir-bars modified with Y shape-duplex DNA probes respectively. In the presence of CAP, the target could recurrently react with the probes on the bars and replace a large amount of long DNA chains into supernatant. After then, the bars were taken out and SYBR green dye was added to the solution. The dye can specifically intercalate into the duplex structures of DNA chains to emit fluorescence while not emitting a signal in its free state. Under the optimized experimental conditions, a wide linear response range of 5 orders of magnitude from 0.001 ng mL -1 to 10 ng mL -1 was achieved with a detection limit of 0.033 pg mL -1 CAP. The assay was successfully employed to detect CAP in food samples (milk & fish) with consistent results with ELISA's. High selectivity and sensitivity were attributed to the zero background signal and triple signal-amplification strategy. Moreover, the detection time can be shortened to 40 min due to that three signal amplified process can occur simultaneously. The fluorescent aptasensor was also label- and enzyme-free. All these ensure the platform to be rapid, cost-effective, easily-used, and is especially appropriate for detection antibiotics in food safety., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Simultaneous and sensitive detection of various antibiotic residues in one sample is essential to evaluation of food safety status. Herein, a multiplexed electrochemical aptasensor for multiplex antibiotics detection, with kanamycin (KANA) and ampicillin (AMP) as representative analytes, was designed by using metal ions encoded apoferrtin probes and double stirring bars-assisted target recycling for signal amplification. The encoded probes were prepared by apoferritin loading Cd 2+ and Pb 2+ ions and labeling with duplex DNAs (aptamers corresponding to KANA and AMP hybrid with its complementary DNA sequence), respectively. In the presence of KANA and AMP, the targets can recurrently react with the probes on the bars, and then replace a lot of Apo-Mencoded signal tags into supernatant. The peak currents of Cd 2+ and Pb 2+ from the tags corresponding with the concentrations of KANA and AMP were detected by square wave voltammetry in one run. As a result, KANA and AMP can be detected simultaneously within the range from 0.05 pM to 50 nM. And the detection limits were 18 fM KANA and 15 fM AMP (S/N = 3). The assay was testified to detect KANA and AMP residues with consistent results of ELISA in samples, e.g. milks and fishes. The assay was highly-sensitive, selective, cost-effective and easy-to-operate due to Apo-M encoded probes with high loading capacity of signal source substances. Moreover, double stirring bar-assisted target recycling, which was enzyme-free and could overcome matrix interference, was fabricated for signal amplification. Thus, the assay showed potential advantages for sensitively screening of antibiotic residues in foods., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Solid phase microextraction (SPME) Arrows with enlarged sorption phases and Arrow-shaped tips are good alternatives to classic SPME fibers. Developing SPME Arrows with functionalized coatings has become a growing area of SPME research. In this study, a zirconium metal organic framework/molybdenum disulfide (UiO-66/MoS 2 ) composite coating modified SPME Arrow was developed and coupled with gas chromatography-mass spectrometry for the headspace extraction and detection of 16 polycyclic aromatic hydrocarbons (PAHs). The coating preparation can be easily manipulated by the assembly strategy using silicone gels to adhere UiO-66/MoS 2 powder onto the surface of the Arrows. The prepared UiO-66/MoS 2 coated SPME Arrows exhibited clearly enhanced adsorption capacity (2.1-4.5 folds) and an improved degree of affinity to PAHs species when compared to commercial PDMS/CARS/DVB SPME Arrows or fibers. The improved mechanism may be due to the high specific area, hierarchical micropores and mesopores, and the largely increased and immobilized amount of UiO-66/MoS 2 coating on the stainless-steel Arrow. Under optimized conditions, the SPME Arrow-based assay was successfully applied to determine PAH levels in fish samples with satisfactory recoveries of 80.2-101% and relative standard deviations (RSDs) of less than 6%. The detection limits of PAHs were between 0.11-1.40 ng kg -1 . The coating showed satisfied reproducibility and repeatability (RSD <8.6%) with only 10 mL of 10% (v/v) acetone in water used as the extraction phase in an effort to be environmentally friendly. All of the results showed that the method is simple, sensitive, and robust. SPME Arrows with UiO-66/MoS 2 coatings can provide new opportunities for the efficient extraction of persistent organic pollutants in food safety applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Excessive intake of kanamycin (KANA) can cause some serious drug-resistant diseases, so it is urgent to develop some accurate and rapid analytical methods for monitor KANA residues in foodstuffs with complex matrix. Recently, many ratiometric assays were reported to be capable of overcoming matrix interference. Herein, a ratiometric and homogeneous assay for KANA detection based on microchip electrophoresis (MCE) was developed. First, by one single strand DNA (S-DNA) and one hairpin DNA (H-DNA), a novel R shape DNA probe (R-DNA) was prepared. After the probe was incubated with KANA, the S-DNA-KANA complex was formed, and H-DNA was released. Moreover, in the presence of exonuclease I (Exo-I), S-DNA-KANA complex would be digested to release the captured KANA for triggering target recycling and signal amplification. With the reaction going on, the fluorescence intensity of H-DNA (I H ) increased and that of R-DNA (I R ) decreased. They can be separated at different voltage intensities and converted to fluorescent signals for signal readout by MCE. The signal ratio of I H /I R was found to be linear toward target from 0.5 pg mL -1 to 10 ng mL -1 , and the limit of detection was 150 fg mL -1 . Moreover, it was successfully employed for KANA detection in milk and fish samples with consistent results of enzyme linked immune sorbent assay (ELISA). The R-DNA probe can quantitatively convert the amount of target to the intensity of DNA without label by MCE, and achieved exonuclease assisted signal amplification in homogenous solution. It was valuable to detect antibiotics residues in foodstuff with complex matrix. This approach broadened the application field of MCE to detect antibiotics without derivatization, which provided a promising platform for rapid screening of antibiotic residues in food., (Copyright © 2018 Elsevier B.V. All rights reserved.)

It's crucial to develop some simple, selective and rapid extraction pretreatments for detection of trace polychlorinated biphenyls (PCBs) residues in soils. Herein, a new magnetic mesoporous titanium dioxide@covalent organic frameworks (Fe 3 O 4 @mTiO 2 @COFs) composite coating was fabricated and adsorbed onto a Nd-Fe-B magnet for headspace sorptive extraction (HSSE) of seven indicative PCBs (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153 and PCB180) in soils. The coating was assembled layer by layer using hydrothermal method. After being extracted by the magnetic stir bar, the adsorbed PCBs can be desorbed in thermal desorption unit (TDU) and measured by gas chromatography-mass spectrometry (GCMS). Under the optimal conditions, the limit of detection (S/N = 3) was measured less than 0.06 ng/g and the linear range was from 0.01 to 100 ng/g. The new coating exhibited good extraction capacity (its saturated adsorption amount was found to be 35 mg/g), selectivity and can be reused for at least 80 times with a recovery above 90%. The HSSE assay showed the following distinctive advantages: Firstly, the outer COFs coating has a uniform size of cavities (about 3.9 nm), thus PCBs (less than 2 nm) can freely pass through them, while the larger macromolecules can be effectively excluded. Secondly, the inner flower-like mTiO 2 coating has good affinity towards chlorine-containing organic compounds, which further improves the selectivity for PCBs. Thirdly, both mTiO 2 and COFs have large specific surface area. The synergistic effects of the composite coating make the HSSE assay exhibit high capacity, selectivity and prominent sensitivity towards PCBs detection coupling with TDGCMS. Finally, it is an environmentally friendly pretreatment method that does not require any organic solvents., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An ultrasensitive colorimetric aptasensor was developed for antibiotics detection, with chloramphenicol (CAP) as model target, using DNAzyme labeled Fe-MIL-88-Pt as novel peroxidase mimic signal tags and target-triggered circular strand-displacement polymerization (CSDP) for signal amplification. The system consists of two components which can partially hybridize with each other: one is capture probe which was formed through immobilizing hairpin DNA containing aptamer sequence on magnetic beads (MB-cDNA), another is signal tag which was constructed through labeling single strand DNAzyme (G-quadruplex/Hemin) which can partially hybrid with cDNA on platinum nanoparticles functionalized Fe-MIL-88 (MIL-88-Pt-DNAzyme). All components of MIL-88, Pt and DNAzyme in the tag can act as peroxidase mimic to triply catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H 2 O 2 into a blue-colored oxidized TMB (oxTMB) for the colorimetric readout. Thus distinctive signal can be observed by naked eye even in presence of 0.02 nM tags. In the presence of target and primer, cDNA loop can open to form cDNA/CAP intermediates, enabling primer to hybridize with the exposed sequences of the cDNA, which initiated target assisted CSDP recycles. Then numerous signal tags were released into supernatant to catalyze TMB for color development. There was a liner relationship between the absorbance and the concentration of CAP in the range of 0.1 pM (0.0323 pg/mL) to 1000 pM (323 pg/mL) with the detection limit of 0.03 pM (0.0097 pg/mL). The ultra-high sensitivity was ascribed to the multiplex catalytic activities from the tags and CSDP based signal amplification. Furthermore, this method can produce signals being observed by naked eye to facilitate in-situ detection and be further extended to detect other antibiotics in food just by simply replacing cDNA on the sensing system., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In the study, a novel two dimensional metal-organic framework (Cu-TCPP nanosheets) based fluorescence resonance energy transfer (FRET) aptasensing platform was developed for detecting antibiotics. Cu-TCPP nanosheets were employed for quenching the background fluorescence and circular strand-replacement DNA polymerization (CSRP) for signal amplification. To fulfill the purpose, we designed an aptamer hairpin probe (HP) whose stem can be opened while specifically binding to target. Then the opened HP would bind with the primer. Under the action of polymerase, extension reaction was induced to generate double-stranded DNA (dsDNA), and then the target was released for the next cycle. Finally, SYBR Green I (SG) can bind with dsDNA to produce strong fluorescence response for quantification of target. It's worth mentioning that the fluorescence of HP/SG complex and free SG could be completely quenched by Cu-TCPP nanosheets while that of dsDNA/SG complex wouldn't be affected. Thus, the sensor produced negligible background signals. It can produce 7.5-fold improved S/N compared to a graphene oxide (GO)-based FRET aptasensor. Chloramphenicol (CAP) was chosen as the model analyte to demonstrate the feasibility of the sensor system. The detection range is broad from 0.001 to 10 ng mL -1 with a detection limit down to 0.3 pg mL -1 . The proposed assay was label free and can be used in homogenous detection which greatly simplifies the complexity of operations. The strategy opens a new way to develop sensitive, in-situ and simple assay for antibiotics in foods., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An ultrasensitive electrochemical aptasensor for multiplex antibiotics detection based on endonuclease and exonuclease assisted dual recycling amplification strategy was proposed. Kanamycin and chloramphenicol were selected as candidates. Firstly, aptamers of the antibiotics were immobilized on bar A and then binding with their endonuclease labeled complementary DNA strands to construct enzyme-cleavage probes. Secondly, The nano zirconium-metal organic framework (NMOF) particles with 1,4-benzene-dicarboxylate (BDC) as linker was defined as UiO-66. And its updated version, hierarchically porous UiO-66 (HP-UIO-66) decorated with different electroactive materials as signal tags were synthesized. Then they were immobilized on bar B linked by two duplex DNA strands which can be specifically cleaved by corresponding enzyme-cleavage probes in bar A. Once targets were introduced into system, aptamers can capture them and then release enzyme-cleavage probes. In the presence of exonuclease-I, exonuclease assisted target recycling amplification was triggered and more enzyme-cleavage probes were released into solution. The probes can trigger endonuclease assisted recycles and repeatedly cleave their corresponding duplex DNA strands on bar B then released numerous signal tags into supernatant. Thus two recycling amplification was performed in the system. Finally, MB and Fc in the signal tags were detected by square wave voltammetry after removing bar A/B and the current intensities were correspondent with the concentration of KANA and CAP respectively. Under the optimum condition, the limits of detection for the KANA and CAP were 35fM and 21fM respectively with a wide linear range from 1 × 10 -4 to 50nM. This dual recycling amplification detection system exhibited high sensitivities and specificity. It can be easily extended to detect other targets if changing the corresponding aptamers and has potential application values for screening of multiplex antibiotics residues in food safety., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this work, the molybdenum disulfide/reduced graphene oxide (MoS 2 /RGO) composite material was synthesized as a fiber coating to extract seven indicator polychlorinated biphenyls (PCBs; PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) present in food via a saponification-headspace solid-phase microextraction assay (saponification-HS-SPME). The MoS 2 /RGO coating was prepared and deposited on a stainless steel wire with the help of a silicone sealant and used as an SPME fiber. The alkali solution dissolved the fat and helped in releasing the PCBs present in milk to the headspace for extraction under 100°C. Following desorption in the inlet, the targets were quantified by gas chromatography-mass spectrometry. The effects of sorbent dosage, extraction time, added salts, and stirring rate on the extraction efficiency were investigated. The new coating was able to adsorb a higher amount of analytes, which was about 1.1-2.9 times in comparison with the commercially available SPME fiber (coated with divinylbenzene/carboxen/polydimethylsiloxane). It also showed the highest adsorption capability toward PCBs, which was 1.5-2.7 times that of the prepared RGO modified fiber. Moreover, MoS 2 also showed a strong affinity toward PCBs in a manner similar to its affinity for graphene. The developed method is simple and environmentally friendly as it does not require any organic solvents. Furthermore, it exhibits good sensitivity with detection limits less than 0.1ngmL -1 , linearity (0.25-100ngmL -1 ), and reproducibility (relative standard deviation below 10% for n=3). The novel SPME fibers are inexpensive, reusable, and can be easily prepared and manipulated. In addition, the saponification-HS-SPME assay was also found to be suitable for screening persistent organic pollutants in dairy products., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this work, a novel aptamer functionalized magnetic adsorbent was developed and combined with magnetic dispersive solid phase extraction (MDSPE) for selective enrichment of several amphenicol antibiotics residues (chloramphenicol(CAP), thiamphenicol(TAP) and florphenicol(FF)) in foodstuff then determined by High Performance Liquid Chromatography (HPLC)-Diode array detector(DAD). Firstly, a magnetic silica-coated Fe 3 O 4 microsphere(Fe 3 O 4 @SiO 2 ) was synthetized by sol-gel method, then it was functionalized by amino groups through 3-Aminopropyltriethoxysilane (APTES) reagent to form Fe 3 O 4 @SiO 2 -NH 2 ; Thirdly, the amino group on Fe 3 O 4 @SiO 2 -NH 2 was transferred to carboxylic group via the succinic anhydride to form Fe 3 O 4 @SiO 2 -COOH. Finally a kind of DNA aptamer with amino group which can simultaneously recognize CAP, TAP, FF, was functionalized on Fe 3 O 4 @SiO 2 -COOH through adding the EDC/sulfo-NHS coupling reagent (Fe 3 O 4 @SiO 2 @Apt). Therefore, a very stable and useful adsorbent was synthesized for the detection of chloramphenicol series antibiotics. This adsorbent can specifically and simultaneously recognize and enrich CAP, TAP, and FF with high adsorption amount from some complicated food matrix, e.g. milk based on the high affinity of aptamer towards the analytes. The saturated extraction capacities for CAP, TAP and FF by the adsorbent were 2.82, 2.56, 2.72μg/g (mass of target/adsorbent)respectively and the enrichment folds were more than 100 times. Afterwards, the target analytes were washed away by pH 8.5 0.1M Tris-HCl buffer solution and detected by HPLC-DAD. The parameters including extraction temperature, extraction capacity, extraction & desorption pH, extraction & desorption time were investigated. With the optimized conditions, the limits of detection (LOD) and limits of quantitation (LOQ) were 0.12-0.17ng/ml and 0.40-0.55ng/ml for the amphenicols in milk. The adsorbent also has good reproducibility for extraction which can be reused at least for 60 cycles with the recovery over 80% (Fig. S2). The MDSPE combined with HPLC-DAD detection possessed the advantages of high selectivity, extraction capacity and very convenient for magnetic separation. In addition, this method is environment friendly and employed no organic solution in the period of pretreatment and extracting. It is a universal platform which can be extended to selective enrichment other organic pollutants residues if changing the modified aptamers., (Copyright © 2017. Published by Elsevier B.V.)

A novel label-free, universal, and high throughput aptasensor was developed based on a microchip electrophoresis (MCE) platform for automatic detection of antibiotic residues in food. Firstly, chloramphenicol (CAP) was employed as a model to be captured by its aptamer probe (Apt). Then, the partial complementary oligonucleotide of CAP's aptamer (C-DNA) was introduced into the reaction system. Because the Apt-CAP complex can't further hybrid with free C-DNA, the amount of hybrid Apt-C-DNA double strand DNA (dsDNA) was less than that without adding the target. Finally, the above mixture was introduced into the microchip electrophoresis (MCE) platform for detection, both dsDNA and Apt-CAP can be separated and produce different fluorescence signals in the MCE. In a certain concentration range, the ratio of signal between dsDNA and Apt-CAP (I dsDNA /I Apt-CAP ) was proportional to the concentration of targets. Under the optimum conditions, the ratio showed a satisfactory linearity range from 0.008 to 1ng/mL of CAP with a detection limit of 0.003ng/mL. Thus, a universal MCE-based assay was developed for quantifying CAP automatically. The method was also successfully applied in the different food samples for CAP detection, which showed a good recovery (Milk: 91.1-108%, Fish: 86.1-114%) and the results were consistent with that of ELISA. This method owned many merits as follows: firstly, MCE was a high throughput screening platform and the detection time is limited to 3min for each sample. Secondly, the aptamer probes can be directly used for detection without labeling any signal tag which can facilitate the preparation procedures of probes. Thirdly, the operation was easy just by the following steps: firstly, the mixture of aptamer probes were incubated followed adding C-DNA; then measurement was performed. Moreover, the assay with MCE platform can be used to detect other targets just by changing the corresponding aptamer probe; it can even realize simultaneous detection when the targets have aptamers with different number of base pairs. Above all, it's a high- throughput and prospective method which can be applied in high throughput screening of antibiotics in food safety., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Some harmful aliphatic diamines, e.g., putrescine (Put) and cadaverine (Cad), play important roles in food safety evaluation. In this study, we proposed on-fiber derivatization solid-phase microextraction analysis of non-volatile aliphatic diamines in fish using zeolitic imidazolate framework 8 (ZIF-8) as a solid-phase microextraction (SPME) coating. It was employed to encapsulate isobutyl chloroformate (IBCF, 40°C, 15min) for aqueous extraction of Put and Cad. After that, the derivatized aliphatic amines were thermally desorbed in the GC injection port and analyzed by GC-MS. The porous and hydrophobic ZIF-8 with high surface area can increase the IBCF loading amount and prevent it from decomposing, thus increasing the amine extraction effectiveness and sensitivity. In SIM mode and using the molecular ion for quantification, the limits of detection for Put and Cad were 27.1 and 33.2μgL -1 , respectively under the optimal conditions. The fiber-to-fiber reproducibility values (RSDs) for three ZIF-8 coated fibers were less than 11.4% for both Put and Cad. The extraction with the new fiber was reproducible for at least 30 cycles without a noticeable decrease of performance (RSD<10%). The new fiber was successfully applied to the detection of putrescine and cadaverine in several fish samples and showed good recoveries (78.6-104%)., (Copyright © 2016 Elsevier B.V. All rights reserved.)

An ultrasensitive electrochemical aptasensor for simultaneous detection of oxytetracycline (OTC) and kanamycin (KAN) has been developed based on metal ions doped metal organic frame materials (MOFs) as signal tracers and RecJ f exonuclease-catalyzed targets recycling amplification. The aptasensor consists of capture beads (the anti-single-stranded DNA Antibody, as anti-ssDNA Ab, labeled on Dynabeads) and nanoscale MOF (NMOF) based signal tracers (simplified as Apts-MNM, the NMOF labeled with metal ions and the aptamers). Particularly, the MOF (UiO-66-NH 2 ), with large internal surface areas, ultrahigh porosity and abundant amine groups in the pores, was employed as substrates to carry plenty of metal ions (Pb 2+ or Cd 2+ ) and label aptamers of OTC or KAN. Thus, the aptasensor is formed by the specific recognition between anti-ssDNA Ab and aptamers. In the presence of targets (OTC and KAN), aptamers prefer to form targets-Apts-MNM complexes in lieu of anti-ssDNA Ab-aptamer complexes, which results in the dissociation of Apts-MNM from capture beads. With the employment of RecJ f exonuclease, targets-Apts-MNM in supernatant was digested into mononucleotides and liberated the target, which can further participate in the next reaction cycling to produce more signal tracers. After magnetic separation, the enhanced square wave voltammetry (SWV) signals were produced from signal tracers. The aptasensor exhibited a linear correlation in the range from 0.5pM to 50nM, with detection limits of 0.18pM and 0.15pM (S/N=3) toward OTC and KAN respectively. This strategy provides specificity and sensitive approach for multiplex antibiotics detection and has promising applications in food analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Electrochemical polymerization of luminol molecularly imprinted polymer on carboxyl graphene (MIP/CG) was developed as stir bar sorptive extraction (SBSE) coating for selective pre-concentration and specific recognition of bisphenol A (BPA), hexoestrol and diethylstilbestrol in milk samples. Luminol was employed as monomer and BPA as the template to prepare MIP under 0-0.6V electro-polymerization. Carboxyl graphene was modified on pencil lead as the substrate to increase extraction capacity. The preparation and extraction conditions affecting the extraction efficiency were optimized. Under the optimized conditions, a good linearity of three estrogens was obtained in the range of 4-1000ngmL(-1). The average recoveries at the three spiked levels of the three estrogens ranged from 83.4% to 96.3% with the relative standard deviations (RSD)≤7.1%. The limits of detection were in the range of 0.36-1.09ngmL(-1). The developed method with low cost, high selectivity and good reproducibility can be potentially applied for determining trace estrogens in complex food samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, a novel homogeneous and signal "off-on" aptamer based fluorescence assay was successfully developed to detect chloramphenicol (CAP) residues in food based on the fluorescence resonance energy transfer (FRET). The vesicle nanotracer was prepared through labeling single stranded DNA binding protein (SSB) on limposome-CdSe/ZnS quantum dot (SSB/L-QD) complexes. It was worth mentioning that the signal tracer (SSB/L-QD) with vesicle shape, which was fabricated being encapsulated with a number of quantum dots and SSB. The nanotracer has excellent signal amplification effects. The vesicle composite probe was formed by combining aptamer labeled nano-gold (Au-Apt) and SSB/L-QD. Which based on SSB's specific affinity towards aptamer. This probe can't emit fluoresce which is in "off" state because the signal from SSB/L-QD as donor can be quenched by the Au-aptas acceptor. When CAP was added in the composite probe solution, the aptamer on the Au-Apt can be preferentially bounded with CAP then release from the composite probe, which can turn the "off" signal of SSB/L-QD tracer into "on" state. The assay indicates excellent linear response to CAP from 0.001 nM to 10 nM and detection limit down to 0.3 pM. The vesicle probes with size of 88 nm have strong signal amplification. Because a larger number of QDs can be labeled inside the double phosphorus lipid membrane. Besides, it was employed to detect CAP residues in the milk samples with results being agreed well with those from ELISA, verifying its accuracy and reliability., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this paper, a novel dispersive solid phase extraction (dSPE) adsorbent based on aptamer-functionalized magnetic metal-organic framework material was developed for selective enrichment of the trace polychlorinated biphenyls (PCBs) from soil sample. Firstly, we developed a simple, versatile synthetic strategy to prepare highly reproducible magnetic amino-functionalized UiO-66 (Fe3O4@PDA@UiO-66-NH2) by using polydopamine (PDA) as covalent linker. Then amino-functionalized aptamers which can recognize 2,3',5,5'-tetrachlorobiphenyl (PCB72), 2',3',4',5,5'-pentachlorobiphenyl (PCB106) were covalent immobilized on UiO-66-NH2 through coupling reagent of glutaraldehyde. Aptamer-functionalized adsorbent (Fe3O4@PDA@UiO-66-Apt) can specifically capture PCBs from complex matrix with high adsorption capacity based on the specific affinity of aptamer towards target. Moreover, the adsorbent can be easily isolated from the solution through magnetic separation after extraction. Afterwards, the detection was carried out with gas chromatography tandem mass spectrometry (GC-MS). The selective dSPE pretreatment coupled with GC-MS possessed high selectivity, good binding capacity, stability, repeatability and reproducibility for the extraction of PCBs. Furthermore, the adsorbent possessed good mechanical stability which can be applied in replicate at least for 60 extraction cycles with recovery over 80%. It provided a linear range of 0.02-400ngmL(-1) with a good correlation coefficient (R(2)=0.9994-0.9996), and the limit of detection was found to be 0.010-0.015ngmL(-1). The method was successfully utilized for the determination of PCBs in soil samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A selective and facile fluorescence "switch-on" scheme is developed to detect antibiotics residues in food, using chloramphenicol (CAP) as model, based on a novel magnetic aptamer probe (aptamer-Pt-luminol nanocomposite labeled with hemin/G-quadruplex). Firstly, the composite probe is prepared through the immuno-reactions between the capture beads (anti-dsDNA antibody labeled on magnetic Dynabeads) and the nanotracer (nano-Pt-luminol labeled with double-strand aptamer, as ds-Apt, and hemin/G-quadruplex). When the composite probe is mixed with CAP, the aptamer preferentially reacted with CAP to decompose the double-strand aptamer to ssDNA, which cannot be recognized by the anti-dsDNA antibody on the capture probes. Thus, after magnetic separation, the nanotracer can be released into the supernatant. Because the hemin/G-quadruplex and PtNPs in nanotracer can catalyze luminol-H2O2 system to emit fluorescence. Thus a dual-amplified "switch-on" signal appeared, of which intensity is proportional to the concentration of CAP between 0.001 and 100ng mL(-1) with detection limit of 0.0005ng mL(-1) (S/N=3). Besides, our method has good selectivity and was employed for CAP detection in real milk samples. The results agree well with those from conventional gas chromatograph-mass spectrometer (GC-MS). The switch-on signal is produced by one-step substitution reaction between aptamer in nanotracer and target. When the analyte is changed, the probe can be refabricated only by changing the corresponding aptamer. Thus, all features above prove our strategy to be a facile, feasible and selective method in antibiotics screening for food safety., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this paper, a novel aptamer-functionalized stir bar sorptive extraction (SBSE) was developed for selective enrichment of the low abundance polychlorinated biphenyls (PCBs) from fish samples. This approach was based on the immobilization of aptamer which could recognize 2,3',5,5'-tetrachlorobiphenyl (PCB72) and 2',3',4',5,5'-pentachlorobiphenyl (PCB106) on one kind of metal-organic frameworks (Zn4O(BDC)3, MOF-5). MOF-5 as a substrate was prepared by potential-controlled cathodic electrodeposition on stainless steel. This aptamer-functionalized stir bar sorptive extraction (Apt-MOF SBSE) fiber could be facile synthesized in one-step. PCB72 and PCB106 were employed as target analytes for selective extraction by the developed method. The adsorbed targets could be desorbed easily in pH 3.0 100mM glycine-HCl buffers and then extracted by the methylene chloride. Afterwards, the detection was carried out with gas chromatography-tandem mass spectrometry (GC-MS). The Apt-MOF SBSE pretreatment coupled with GC-MS exhibited high selectivity, good binding capacity, stability and reproducibility for the detection of PCBs. It provided a linear range of 0.02-250ngmL(-1) with a good coefficient of determination (R(2)=0.9991-0.9996) and the detection limit was 0.003-0.004ngmL(-1). More importantly, the method was successfully utilized for the determination of PCBs in fish samples with good enrichment factor (1930-2304). Therefore, this new SBSE coating opens up the possibility of selective enrichment of a given target PCBs from complex fish samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this work, several kinds of the metal-organic framework (MOF) were evaluated the adsorption performance to PCB. Finally, MOF-5(Fe) was introduced in stir bar sorptive extraction (SBSE) as the adsorbent to extract six polychlorinated biphenyls (PCBs). Nd-Fe-B permanent magnet was employed as stir bar, which was then coated with Fe3O4-MOF-5(Fe) composite magnetic material, which was prepared by solvothermal method. The stir bar was then employed to extract and enrich six indicator PCBs (2,2',5,5'-tetrachlorobiphenyl, 2,2',4,5,5'-pentachlorobiphenyl, 2,2',3,4,4',5-hexachlorobiphenyl, 2,3,4,4,5-pentachlorobiphenyl, 2,2',4,4',5,5'-hexachlorobiphenyl, 2,2',3,4,4',5,5'-heptachlorobiphenyl) under stirring, then eluted by n-hexane under ultrasound. Its saturated adsorption amount was found to be 17.0-17.8 mg g(-1) and only 30 min were needed to reach adsorption equilibrium. The MOF-stir bar can be reused for 60 times with the recovery above 80%, which exhibited good stability. Under the optimal experimental conditions, MOF-5(Fe) based SBSE was coupled with GC-MS for detecting six PCBs. The limits of detection (S/N=3) of the developed method were 0.061-0.096 ng g(-1), with enrichment factors of 50-100 fold. And the linear ranges were 0.01-500 μg L(-1). The new method was successfully applied to assess PCBs in fish samples with satisfactory recovery ranging from 94.3% to 97.5%., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A high-performance and selective adsorbent was developed for simultaneous extraction of 6 chlorobenzenes residues in soil samples by using magnetic solid phase extraction (MSPE) combined with automated SPE followed by gas chromatography-mass spectrometry (GC-MS). The adsorbent was synthesized by grafting carboxymethyl-β-cyclodextrin (CM-β-CD) on the surface of porous core-shell magnetic Fe3O4@flower like TiO2 microspheres (Fe3O4@fTiO2-CMCD), used as a carrier. The main factors (adsorbent amount, adsorption time, elution solvent, elution volume, and elution flow rate) affecting the extraction efficiency were investigated in detail. The adsorbent exhibited high loading capacity (25.6 mg g(-1) for 1,3-dichlorobenzene). This maybe due to meso-/macroporous TiO2 having high specific surface area; as a carrier of the β-cyclodextrin film, it could obviously increase the number of recognition sites. The newly developed adsorbent also showed good selectivity towards chlorobenzenes based on host-guest interactions between β-cyclodextrin (on adsorbent's surface) and targets, which can minimize complex matrix interference in soil samples. The proposed method was successfully applied for the analysis of environmental soil samples with recovery ranging from 87.3 to 104.3%. All target compounds showed good linearities with correlation coefficients (r) higher than 0.996. The limits of quantitation for the 6 CBs were 0.03-0.09 μg kg(-1). These findings confirmed meso-/macroporous structure Fe3O4@fTiO2-CMCD as a highly effective extraction material for use in trace CB analyses in complex soil samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this study, we developed a magnetically multifunctional purifying material for efficient removal of matrix interferences, especially certain organochlorine pesticide (DDT, DDE, and DDD), during the determination of toxic highly chlorinated polychlorinated biphenyls (PCBs) at trace levels in soil samples. The multifunctional adsorbent (CMCD-NH2-MNPs) was prepared by grafting carboxymethyl-β-cyclodextrin on the surface of amino-functionalized magnetite (Fe3O4) nanoparticles. CMCD-NH2-MNPs has stronger host-guest complexation with DDT, DDE, and DDD, but the same adsorbent shows weaker adsorption ability toward highly chlorinated PCBs (from tetra- to octa-chlorinated PCBs) owing to their steric hindrance effect. Based on this principle, a simple and rapid gas chromatography-mass spectrometry (GC-MS) method was developed for six indicator PCBs (PCB28, PCB52, PCB101, PCB138, PCB153, and PCB180) in soil. Comparative studies were conducted to determine the clean-up efficiency of the following three techniques: (i) Oasis-HLB, (ii) multi-layer silica column, and (iii) dSPE employing CMCD-NH2-MNPs. The results indicate that CMCD-NH2-MNPs as the purification material can easily and effectively remove DDT, DDE, and DDD in soil samples within a short duration of time. The recoveries for highly chlorinated PCBs were in the range of 85.4-102.2%, with RSDs varying between 1.0 and 6.5%. The proposed method was verified as one of the most effective clean-up procedures for the analysis of highly chlorinated PCBs in real soil samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Analysis of tributyltin chloride (TBT) in environmental samples, such as seawater, is important in order to evaluate the TBT contamination and accumulation in the trophic chain. The environmental impact of organotin compounds has been a particular focus of analytical studies. The present study reports the use of molecular imprinting technology coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine trace amounts of TBT in seawater and seafood (mussel tissue samples). The imprinted polymer was synthesized by a non-covalent free-radical approach using acrylamide (AM) as a monomer and TBT as a template molecule in acetonitrile solvent (polymerization media). The imprinted polymer synthesized by this approach exhibited good adsorptive capacity and allowed specific retention of TBT. Recoveries of TBT in seawater samples spiked with different TBT concentrations ranged from 67.2% to 81.1% with peak area precision (RSD)<3.7%, and recoveries of TBT in mussel tissue samples ranged from 75.0% to 94.2% with RSD<4.8%., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of α-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe(3)O(4)-Au nanoparticles, which was first employed to capture AFP antigens to form Fe(3)O(4)-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe(3)O(4)-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe(3)O(4)-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0 ng mL(-1) with a detection limit of 0.2 pg mL(-1). The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the amplification of the signal tag, the immunosensor is highly sensitive, which can offer great promise for rapid, simple, selective and cost-effective detection of effective biomonitoring for clinical application., (Copyright © 2012 Elsevier B.V. All rights reserved.)