Immobilization of a broad host range phage on the peroxidase-like Fe-MOF for colorimetric determination of multiple Salmonella enterica strains in food.

A broad host range phage-based nanozyme (Fe-MOF@SalmpYZU47) was prepared for colorimetric detection of multiple Salmonella enterica strains. The isolation of a broad host range phage (SalmpYZU47) capable of infecting multiple S. enterica strains was achieved. Then, it was directly immobilized onto the Fe-MOF to prepare Fe-MOF@SalmpYZU47, exhibiting peroxidase-like activity. The peroxidase-like activity can be specifically inhibited by multiple S. enterica strains, benefiting from the broad host range capture ability of Fe-MOF@SalmpYZU47. Based on it, a colorimetric detection approach was developed for S. enterica in the range from 1.0 × 102 to 1.0 × 108 CFU mL-1, achieving a low limit of detection (LOD) of 11 CFU mL-1. The Fe-MOF@SalmpYZU47 was utilized for detecting S. enterica in authentic food samples, achieving recoveries ranging from 91.88 to 105.34%. Hence, our proposed broad host range phage-based nanozyme exhibits significant potential for application in the colorimetric detection of pathogenic bacteria.

Anthropogenic effects on soils in the eastern Tibetan Plateau revealed by geochemical elemental characteristics.

The Tibetan Plateau (TP) constitutes a fragile and sensitive ecological environment, which is vulnerable to global climate change and human activities. To investigate the anthropogenic effects on the TP's environmental system is valuable for guiding human responses and adaptations to future environmental changes. In this study, we detailedly analyzed the geochemical elements of four representative soil sections developed on loess from Ganzi, Jinchuan, Aba, and Chuanzhusi in the eastern TP. The chemical elemental profiles distinctly indicated the presence of typical anthropogenic elements (Cu, Zn, Ni, Cr, Pb, Mn, and Fe), underscoring the substantial influence of human activities on TP soil, and showing spatial variance. Our results indicate that anthropogenic impacts were relatively low at Aba and Ganzi, resulting in a deficit of anthropogenic elements at the surface layer. Whereas at Jinchuan and Chuanzhusi, relatively intense anthropogenic impacts have led to the enrichment of anthropogenic elements in the topsoil. We infer that agricultural activities, increased traffic, and expansion of tourism activities were the major factors affecting the anthropogenic elements of TP soils. Our study highlights the impact of human activities on soil geochemical processes in the Tibetan Plateau.

Bimetallic AuNR@AgNCs for ultrasensitive surface-enhanced Raman scattering sensing of dithianon in apple juice.

In this study, a bimetallic surfaced-enhanced Raman spectroscopy (SERS)-active substrate consisting of AuNR@AgNCs was proposed for the rapid detection of dithianon. Due to the significant synergistic enhancement of the core-shell nanocuboids, the obtained AuNR@AgNC substrate exhibited excellent SERS performance. The simulation findings supported the practical SERS results and demonstrated that interactions were mainly maintained by the nitrile functional group. The AuNR@AgNCs could be used to detect dithianon with an LOD value of 20 nM. Moreover, dithianon in river water and apple juice could be detected with recovery in the satisfactory ranges of 97.41%-98.35% and 97.77%-98.70%, respectively, by using this substrate under optimal conditions, indicating that the AuNR@AgNC substrate could serve as an excellent SERS detection platform for pesticide residues in fruit.

Competitive immunoassay using enzyme-regulated Fe3O4@COF/Fe3+ fluorescence probe for natural chloramphenicol detection.

Accurate and sensitive detection of chloramphenicol (CAP) in natural samples is essential for ensuring human health. Herein, an enzyme-regulated fluorescence sensor using Fe3O4@COF/Fe3+ probe, is developed for CAP determination. Fe3O4@COF, synthesized via hydrothermal method, exhibits dual functions as a magnetic carrier and signal probe. Bovine serum albumin conjugated-chloramphenicol, adsorbed on the surface of Fe3O4@COF, competes with CAP for antibody binding. The antibody interacts with alkaline phosphatase via the biotin-streptavidin system. Meanwhile, ascorbic acid, produced from the enzyme-catalyzed reaction dominated by alkaline phosphatase, effectively restores the fluorescence of Fe3O4@COF that is quenched by Fe3+. After experimental verification and gradual optimization, a logarithmic linear relationship between CAP concentration and fluorescence intensity is established in the range of 2 × 10-4∼10 µg mL-1, with a good limit of detection (9.2 × 10-5 µg mL-1). Proposed method exhibits excellent stability (15 days) and reusability (8 cycles), providing a sensitive and reliable method for accurate CAP detection. The readouts show good agreement with HPLC and recoveries during laboratory and natural CAP analysis.

An advanced ratiometric molecularly imprinted sensor based on metal ion reoxidation for indirect and ultrasensitive glyphosate detection in fruit.

An indirect and ultrasensitive ratiometric molecularly imprinted (MIP) sensor, based on metal ion reoxidation, is introduced for glyphosate (GLY) determination in fruit. As high-performance signal amplification substrates, carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) are conveniently modified on GCE. The artificial antibody-MIP membrane, presents typical three-dimensional structure to GLY template. Built-in reference methylene blue (MB) is directly electropolymerized on MWCNTs-Au/GCE. Particularly, Cu2+ and GLY interestingly form chelate complex, and the Cu2+ (ICu) in Cu(Ⅱ)-GLY-complex can be reoxidized, and indirectly quantizes GLY. The reference signal (IMB) presents noteworthy stability with different GLY levels, and the ratiometric readout (ICu/IMB) is recognized as a more trustworthy indicator to quantize GLY. Proposed sensor presents broad range as 1.73 âˆ¼ 400 ng/mL, and limit of detection is well found as 0.24 ng/mL (S/N = 3). Finally, as-fabricated method is verified with standard HPLC in real-fruit-sample, and the errors and recovery rates are calculated as 3.4% âˆ¼ 6.7% and 94.4% âˆ¼ 104.6%, respectively.

Surface engineering of magnetic peroxidase mimic using bacteriophage for high-sensitivity/specificity colorimetric determination of Staphylococcus aureus in food.

Herein, we proposed surface engineering of magnetic peroxidase mimic using bacteriophage by electrostatic interaction to prepare bacteriophage SapYZU15 modified Fe3O4 (SapYZU15@Fe3O4) for colorimetric determination of S. aureus in food. SapYZU15@Fe3O4 exhibits peroxidase-like activity, catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. After introducing S. aureus, peroxidase-like activity of SapYZU15@Fe3O4 was specifically inhibited, resulting in deceleration of TMB chromogenic reaction. This phenomenon benefits from the presence of unique tail protein gene in the bacteriophage SapYZU15 genome, leading to a specific biological interaction between S. aureus and SapYZU15. On basis of this principle, SapYZU15@Fe3O4 can be employed for colorimetric determination of S. aureus with a limiting detection (LOD), calculated as low as 1.2 × 102 CFU mL-1. With this proposed method, colorimetric detection of S. aureus in food was successfully achieved. This portends that surface engineering of nanozymes using bacteriophage has great potential in the field of colorimetric detection of pathogenic bacterium in food.

Versatile dodecyl trimethyl ammonium bromide modified γ-FeOOH for simultaneous removal and determination of As(⠤).

Inorganic arsenic pollution in water spreads all over the world, tremendously threatening environmental safety and human health. Herein, versatile dodecyl trimethyl ammonium bromide modified γ-FeOOH (DTAB-γ-FeOOH) was prepared for sportive removal and visual determination of As(Ⅴ) in water. DTAB-γ-FeOOH displays a nanosheet-like structure with a high specific surface area calculated as 166.88 m2 g-1. Additionally, DTAB-γ-FeOOH shows peroxidase-mimicking feature, which can catalyze colorless TMB to generate blue oxidized TMB (TMBox) in presence of H2O2. Removal experiments show that DTAB-γ-FeOOH exhibits good As(Ⅴ) removal efficiency because modification of DTAB makes γ-FeOOH carry abundant positive charges, improving affinity between DTAB-γ-FeOOH and As(Ⅴ). It is found that theoretical maximum adsorption capacity is up to 126.91 mg g-1. Moreover, DTAB-γ-FeOOH can resist interference of most of co-existing ions. After that, As(Ⅴ) was detected based on peroxidase-like DTAB-γ-FeOOH. As(Ⅴ) can be adsorbed onto DTAB-γ-FeOOH surface, markedly inhibiting its peroxidase-like activity. Based on it, As(Ⅴ) ranging from 1.67 to 3333.33 µg L-1 can be well detected, with a low LOD (0.84 µg L-1). The successful sorptive removal and visual determination of As(Ⅴ) from real environmental water indicated that DTAB-γ-FeOOH has great potential in the treatment of As(Ⅴ)-containing environment water.

Whole-genome analysis showed the promotion of genetic diversity and coevolution in Staphylococcus aureus lytic bacteriophages and their hosts mediated by prophages via worldwide recombination events.

Prophages as a part of Staphylococcus aureus genome contribute to the genetic diversity as well as survival strategies of their host. Some S. aureus prophages also have an imminent risk of host cell lysis and become a lytic phage. Nonetheless, interactions among S. aureus prophages, lytic phages, and their hosts, as well as the genetic diversity of S. aureus prophages, remain unclear. We identified 579 intact and 1,389 incomplete prophages in the genomes of 493 S. aureus isolates obtained from the NCBI database. The structural diversity and gene content of intact and incomplete prophages were investigated and compared with 188 lytic phages. Mosaic structure comparison, ortholog group clustering, phylogenetic analysis, and recombination network analysis were performed to estimate genetic relatedness among S. aureus intact prophages, incomplete prophages, and lytic phages. The intact and incomplete prophages harbored 148 and 522 distinct mosaic structures, respectively. The major difference between lytic phages and prophages was the lack of functional modules and genes. Compared to the lytic phages, both the S. aureus intact and incomplete prophages harbored multiple antimicrobial resistance (AMR) and virulence factor (VF) genes. Several functional modules of lytic phages 3_AJ_2017 and 23MRA shared more than 99% nucleotide sequence identity with S. aureus intact (ST20130943_p1 and UTSW_ MRSA_55_ip3) and incomplete prophages (SA3_LAU_ip3 and MRSA_FKTN_ip4); other modules showed little nucleotide sequence similarity. Ortholog and phylogenetic analyses revealed a common gene pool shared between the prophages and lytic Siphoviridae phages. Moreover, most shared sequences existed within intact (43428/137294, 31.6%) and incomplete prophages (41248/137294, 30.0%). Therefore, the maintenance or loss of functional modules in intact and incomplete prophages is key to balance the costs and benefits of large prophages harboring various AMR and VF genes in the bacterial host. The shared identical functional modules between S. aureus lytic phages and prophages are likely to result in the exchange, acquisition, and loss of functional modules, and therefore contribute to their genetic diversity. Moreover, constant recombination events within prophages globally were responsible for the coevolution of lytic phages and their bacterial hosts.

A smartphone-integrated colorimetric quantitative analysis platform based on oxidase-like Ce(IV)-ATP-Tris CPNs/CNF test strip for detection of inorganic arsenic in rice.

Herein, a colorimetric sensing system based on cerium(IV) coordination polymer nanoparticles (Ce(IV)-ATP-Tris CPNs) was proposed for As(V) detection. Ce(IV)-ATP-Tris CPNs show excellent oxidase-like activity, triggering 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. With addition of ascorbic acid 2-phosphate (AAP) and acid phosphatase (ACP), ACP can hydrolyze AAP to produce antioxidative ascorbic acid (AA), inhibiting TMB chromogenic reaction. After that, introduction of As(V) can inhibit ACP, recovering TMB chromogenic reaction. Therefore, sensitive and selective As(V) detection is achieved. Moreover, Ce(IV)-ATP-Tris CPNs were transformed into cellulose nanofiber (CNF) to form test strip (Ce(IV)-ATP-Tris CPNs/CNF). Inorganic arsenic in rice can be detected by test strip, color of that can be measured by smartphone-integrated colorimetric quantitative analysis platform. Given this, rapid and convenient strip test of inorganic arsenic in rice by using this platform was achieved. Hence, this platform possesses great application potential in the field of inorganic arsenic in rice, even food safety.

Thermal-controlled active sensor module using enzyme-regulated UiO-66-NH2/MnO2 fluorescence probe for total organophosphorus pesticide determination.

An enzyme-regulated UiO-66-NH2/MnO2 fluorescence sensor, fully functionalized with spectrometric capacities, is developed for budget-friendly total organophosphorus pesticides (OPs) determination. The fluorescence probe, UiO-66-NH2/MnO2, is hydrothermally synthesized and morphologically examined. A specialized enzyme-catalyzed reaction, which can be gradually inhibited by OPs, is designed with participations of alkaline phosphatase (ALP) and sodium L-ascorbyl-2-phosphate (AAP). The reaction product of ascorbic acid (AA) decomposes MnO2 and restores UiO-66-NH2 fluorescence, establishing a relationship between OPs level and fluorescence intensity. Interactions among UiO-66-NH2, MnO2, OPs, and AA are clarified. Stepwise optimizations are performed to the UiO-66-NH2/MnO2 probe, ensuring considerable advantages as OPs affinity and fluorescence quenching behavior over rival nanomaterials. Analytical advances are magnified by fabricating an active sensor module, with self-acting thermal regulation for optimal enzyme activity. Under 4 and 20 °C environment, regulation period is less than 40 and 100 s. In total OPs determination for laboratorial and real-vegetable samples, this method exhibits uniform and log-linear responses to common species of OPs in a range as 1.0 × 10-7~10 mg L-1, and limit of detection is established as 8.9 × 10-8 mg L-1. Proposed readouts are validated with certified HPLC and recovery test. Relative errors and recovery rates are found as 2.7-6.4% and 95.8-102.6%, respectively.

Programmable-Printing Paper-Based Device with a MoS2 NP and Gmp/Eu-Cit Fluorescence Couple for Ratiometric Tetracycline Analysis in Various Natural Samples.

Paper-based fluorescence devices, with smartphone aids, bring considerable operation convenience for tetracycline (TC) sensing. Nevertheless, they must meet the challenge in real determination against complicated backgrounds. Considering that, we present a programmable-printing paper-based device and then apply it to TC determination for various natural samples. MoS2 NPs and Gmp/Eu-Cit are synthetized as composite probes. A static quenching process is found with MoS2 NP fluorescence at 430 nm, while significant magnification of Gmp/Eu-Cit emission is obtained at 617 nm, establishing a valuable ratiometric indicator. Remarkably, two-stage programmable printing maximizes the proposed sensing capability. A transitive device, containing a gradually changing amount of a certain probe, is prepared to sense TC. With a homemade smartphone application and 3D-printed measurement chamber, the corresponding signals are examined to explore optimal setups. These setups are automatically processed to prepare the final-version device, not requiring manual operations. Benefitting from this interesting feature, the proposed device gains many rewards in performances. It effectively senses TC in a wide range from 12.7 nM to 80 µM and simultaneously provides naked eye-legible signals and smartphone-based readouts with confident selectivity and stability. This device is consequently applied for various samples of soil, river water, milk, and serum and meets well with HPLC-MS and recovery tests.

Target-induced synergetic modulation of electrochemical tag concentration and electrode surface passivation for one-step sampling filtration-free detection of acid phosphatase activity.

As a biomarker of several diseases, the activity of acid phosphatase (ACP) is generally used to assistantly diagnose these diseases. Thus, developing reliable ACP activity analytical methods becomes quite significant. Herein, we recommend a one-step sampling filtration-free electrochemical method for ACP activity determination based on the target-induced synergetic modulation of tag concentration and surface passivation. Mn3O4 microspheres with favorable oxidase-mimicking activity are synthesized to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to its product TMBox, resulting in a remarkable re-reduction signal of TMBox to TMB recorded by an integrated electrochemical system consisting of screen-printed electrode (SPE) and 3D-printed holder. When hexametaphosphate ions (HMPi) with rich negative charges are employed to interact positively charged TMBox, the formed flocculent precipitate TMBox-HMPi automatically sedimentates onto SPE surface, and both the decreased concentration of free TMBox in solution and the increased electrode surface passivation triggered by TMBox-HMPi sedimentation synergistically reduce the re-reduction signal of TMBox. When ACP is present, it hydrolyzes the HMPi substrate, greatly relieving the formation of the TMBox-HMPi precipitate and its sedimentation onto SPE surface. As a result, the electrochemical re-reduction signal of TMBox becomes remarkable again. With the strategy of using one stimulus to generate two-fold signal change, highly sensitive ACP activity detection was realized, with a wide linear range from 0.05 to 50 U/L and a limit of detection down to 0.024 U/L. Reliable monitoring of ACP activity in clinical serum was also demonstrated.

A single-nanozyme colorimetric array based on target-induced differential surface passivation for quantification and discrimination of Cl-, Br- and I- ions.

Abnormal levels of halide ions in drinking water have enormous threats to human health, and thus designing reliable and sensitive methods to quantify and distinguish these ions becomes extremely crucial. Herein, we develop a single-nanozyme colorimetric array based on target-induced differential surface passivation for the quantification and discrimination of Cl-, Br- and I- ions. Silver citrate (Ag3Cit) is designed as an oxidase mimic to efficiently catalyze the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. When halide ions (Cl-, Br- and I-) are present, due to their different precipitation interactions with the Ag(Ⅰ) entity in Ag3Cit, they can passivate the active surface of the nanozyme to various degrees, resulting in the inhibited TMB chromogenic reaction differentially. According to this principle, simple and efficient quantitative detection of Cl-, Br- and I- ions was achieved, with all the detection limits down to the nM level. By employing Ag3Cit as a single sensing element, a nanozyme catalysis-based colorimetric array was further established, and both individual and mixed ions were successfully distinguished by integrating the array with principal component analysis. Accurate identification of unknown samples was also verified via a double-blind protocol, indicating potential applications of the array in practice.

A portable test strip based on fluorescent europium-based metal-organic framework for rapid and visual detection of tetracycline in food samples.

Residual tetracycline (TC) in animal food caused by abuse of antibiotics leads to many chronic diseases in the human body. The development of a simple and on-site visualization method for TC detection is need of the hour. Herein, a fluorescent europium-based metal-organic framework (Eu-MOF) sensor for visual and rapid detection of TC was developed. Eu-MOF displays a red emission being excited at 260 nm. Upon exposure to TC, significant fluorescence quenching was observed due to the inner filter effect and photoinduced electron transfer. Moreover, the developed sensor was applied for the detection of TC in milk and beef samples with recoveries of 96.1% to 106.3%, respectively. More importantly, a portable test strip based on Eu-MOF was manufactured. It is a highly selective and sensitive portable device for TC detection. The results can be distinguished immediately by naked eyes, making it become an excellent choice to detect TC in real-time application.

One-pot construction of acid phosphatase and hemin loaded multifunctional metal-organic framework nanosheets for ratiometric fluorescent arsenate sensing.

Exploring high-performance sensors for toxic arsenic detection is highly desired because of its great threat to the environment. Herein, we report a ratiometric fluorescent biosensor based on acid phosphatase and hemin loaded multifunctional Zn-based metal-organic framework (ACP/hemin@Zn-MOF) for high-performance arsenate (As(Ⅴ)) sensing. ACP/hemin@Zn-MOF is constructed by self-assembly, where hemin exhibits peroxidase-like activity and 2-aminoterephthalic acid ligand endows ACP/hemin@Zn-MOF with an intrinsic fluorescence (452 nm). When ACP/hemin@Zn-MOF catalyzes the oxidation of o-phenylenediamine (OPD), fluorescent 2,3-diaminophenazine (DAP) with an emission signal (564 nm) is produced and weakens ACP/hemin@Zn-MOF intrinsic fluorescence (452 nm) due to inner filter effect; after adding ascorbic acid 2-phosphate (AAP), ACP can hydrolyze AAP and produce ascorbic acid, which competitively suppresses the oxidation of OPD, resulting in the decrease of DAP signal (564 nm) and the recovery of ACP/hemin@Zn-MOF signal (452 nm); when As(V) is added, it irreversibly poisons ACP against hydrolyzing AAP, and the fluorescence signal at 564 nm recovers and the one at 452 nm is suppressed again. High-sensitivity and high-selectivity detection of As(V) (3.33-300 µg L-1) is realized, with a detection limit of 1.05 µg L-1. The biosensor was also successfully employed to detect total arsenic and As(V) in rice.

MicroRNA-603 Promotes Progression of Cutaneous Melanoma by Regulating TBX5.

BACKGROUND: Although studies manifested that microRNA-603 plays a vital role in many cancers, the modulatory mechanism of microRNA-603 in cutaneous melanoma remains unknown. We aimed to investigate the roles of microRNA-603 in cutaneous melanoma cells. METHODS: First, microRNA-603 expression in cutaneous melanoma cell lines was detected by qRT-PCR. The mRNA and protein expression levels of TBX5 in cutaneous melanoma cell lines were tested by qRT-PCR and western blot, respectively. In addition, the interaction between microRNA-603 and TBX5 was determined by dual-luciferase reporter gene assay, and their impacts on the growth of cutaneous melanoma cells were detected by cellular function experiments such as MTT, colony formation, and Transwell assays. RESULTS: The expression level of microRNA-603 in human cutaneous melanoma cells was relatively upregulated. Overexpressing microRNA-603 could promote progression of cutaneous melanoma cells, while silencing microRNA-603 expression could suppress the malignant progression of cutaneous melanoma. In addition, TBX5 was lowly expressed in cutaneous melanoma cells. As confirmed by dual-luciferase assay, microRNA-603 could specifically bind to 3'UTR of TBX5 and regulate TBX5. The results of the rescue experiment demonstrated that inhibiting microRNA-603 expression could suppress the proliferation, migration, and invasion of cutaneous melanoma cells, but its suppressive effect could be restored by TBX5. CONCLUSION: MicroRNA-603 could regulate the expression of TBX5, thus promoting the malignant progression of cutaneous melanoma cells.

Micrometer-scale light-addressable potentiometric sensor on an optical fiber for biological glucose determination.

A novel light-addressable potentiometric sensor (LAPS), on the micrometer scale, is presented for rapid determination of blood and urine glucose. A LAPS chip with <150 µm working diameter is fabricated using standard semiconductor technique, and assembled onto an optical fiber of a laser module to form a micro-sized device. An active circuit design, containing on-board light driver and transimpedance amplifier, is introduced to simplify electronic connection and improve signal quality. Glucose-sensitive layer is obtained by drop-coating glucose oxidase onto the working surface of the LAPS. Under optimized optical and electrochemical conditions, the proposed sensor is used to detect glucose in laboratorial and real samples. In a wide range as 0.01-100 mM, a log-linear relationship is well established, and the response time is less than 10 s. Limit of detection and limit of quantitation of this method are found to be 0.003 and 0.01 mM, respectively. Data from the proposed method are validated with those from a certified clinical analyzer, and no statistic difference is found.

A peroxidase-mimicking Zr-based MOF colorimetric sensing array to quantify and discriminate phosphorylated proteins.

Phosphorylation is a common process for regulating protein functions. Studies have confirmed that many human diseases are associated with the abnormal phosphorylation of proteins. Hence, uncovering the phosphorylation state of proteins turns to be of much importance for biomedicine and clinical practice. In this work, we report a simple but efficient colorimetric sensor array for the quantification and identification of phosphorylated proteins by using a Zr-based MOF as a peroxidase mimic. Thanks to its unique dipyridyl-based ligands, the proposed MOF is able to exhibit favorable catalytic activity to stimulate the chromogenic reaction of H2O2 and 3,3',5,5'-tetramethylbenzidine. When phosphorylated proteins are in presence, they can anchor onto the nanozyme surface via the strong interaction between phosphate groups in proteins and Zr nodes in the MOF, resulting in the inhibition of the nanozyme's activity and the suppression of the chromogenic reaction. Based on this principle, our colorimetric sensor array enabled the facile quantification of phosphorylated proteins. Given that proteins with different phosphorylation states would affect the catalytic activity of the MOF nanozyme in different degrees, we further integrated the array with principal component analysis for the successful identification of phosphorylated and non-phosphorylated proteins.

Construction of a recyclable oxidase-mimicking Fe3O4@MnOx-based colorimetric sensor array for quantifying and identifying chlorophenols.

Chlorophenols (CPs) are known as a class of pollutants posing a great threat to the environment and human health because of their carcinogenesis and teratogenesis, and thus exploring convenient and efficient methods for their detection and identification becomes particularly important. Herein, we report a recyclable colorimetric sensor array according to the oxidase-mimicking catalytic characteristics of Fe3O4@MnOx for the high-performance quantification and differentiation of typical CPs. The core-shell Fe3O4@MnOx prepared by growing oxidase-like MnOx nanoflakes on the surface of magnetic Fe3O4 particles via a hydrothermal process can exhibit excellent catalytic activity to trigger the color reaction of CPs and 4-aminoantipyrine with the participation of O2. By utilizing the Fe3O4@MnOx-catalyzed color reaction, high-sensitivity quantitative analysis of CPs, taking 2-chlorophenol as a model, was realized, providing a detection limit as low as 0.85 µM. Given different chlorine substitution places and numbers in CPs impact the reaction kinetics diversely, a new nanozyme-based colorimetric sensor array was further constructed for the successful differentiation of various CPs with the help of hierarchical cluster analysis and principal component analysis. Accurate double-blind identification of unknown samples using the proposed sensor array was also demonstrated, indicating its reliability for practical practice.

A smart-phone-based electrochemical platform with programmable solid-state-microwave flow digestion for determination of heavy metals in liquid food.

This work introduces an inexpensive and user-friendly electrochemical platform for heavy metal determination in liquid food. Smart-phone connectivity, solid-state-microwave flow digestion and nano-Au-modified electrode are synchronously studied. A smart phone is adopted as the information terminal for universal purposes. A solid-state-microwave digestion device is developed to provide programmable digestion for liquid food in a digestion path. Microwave power curve and flow rate in digestion are studied and optimized. A nano-Au-modified electrode, as well as a homemade potentiostat and other electrodes, is used as a tool for electrochemical analyses. Behaviors of this method are evaluated with electrical measurement and stripping voltammetry. This method is used for sensing Cd2+, Pb2+ and Hg2+ in cow milk, orange juice and apple juice. It provides a sensitive response to ≥2 µg L-1 target ion, and shows satisfying stability and good accuracy in a task up to 72 h.