Multicolor Fluorescent Inks Based on Lanthanide Hybrid Organogels for Anticounterfeiting and Logic Circuit Design.

With the rapid development of information technology, the encrypted storage of information is becoming increasingly important for human life. The luminescent materials with a color-changed response under physical or chemical stimuli are crucial for information coding and anticounterfeiting. However, traditional fluorescent materials usually face problems such as a lack of tunable fluorescence, insufficient surface-adaptive adhesion, and strict synthesis conditions, hindering their practical applications. Herein, a series of luminescent lanthanide hybrid organogels (Ln-MOGs) were rapidly synthesized using a simple method at room temperature through the coordination between lanthanide ions and 2,6-pyridinedicarboxylic acid and 5-aminoisophthalic acid. And the multicolor fluorescent inks were also prepared based on the Ln-MOG and hyaluronic acid, with the advantages of being easy to write, color-adjustable, and water-responsive discoloration, which has been applied to paper-based anticounterfeiting technology. Inspired by the responsiveness of the fluorescent inks to water, we designed a logic system that can realize single-input logic operations (NOT and PASS1) and double-input logic operations (NAND, AND, OR, NOR, XOR). The encryption of a binary code can be actualized utilizing different luminescent response modes based on the logic circuit system. By adjusting the energy sensitization and luminescence mechanism of lanthanide ions in the gel structure, the information reading and writing ability of the fluorescent inks were verified, which has great potential in the field of multicolor pattern anticounterfeiting and information encryption.

Recognition-Activated Primer-Mediated Exponential Rolling Circle Amplification for Signal Probe Production and Ultrasensitive Visual Detection of Ochratoxin A with Nucleic Acid Lateral Flow Strips.

We proposed a visual strategy for rapid and ultrasensitive detection of ochratoxin A (OTA) by integration of primer-mediated exponential rolling circle amplification (P-ERCA) with a designed nucleic acid lateral flow strip (LFS). The recognition component was preimmobilized in the tube by hybridization between the immobilized functionalized aptamer and complementary ssDNA. Recognition of OTA induces the release of complementary ssDNA from the tube, which will also act as the primer of the designed P-ERCA. Three nicking sites on the template P-ERCA could contribute to the production of enormous signal probes based on the simultaneous amplification-nicking model, which can be visually measured directly with the constructed nucleic acid LFS. Importantly, the nicked signal probe can also act as the trigger of the new-round RCA, achieving exponential growth of signal probes for measurement and signal enhancement. Taking advantage of the extraordinary amplification efficiency of P-ERCA and the simplicity of LFS, this P-ERCA-LFS method demonstrates ultrasensitive detection of OTA with a visual limit of detection as low as 100 fg/mL for qualitative screening and a limit of detection of 35 fg/mL for semiquantitative analysis. This designed strategy could also be utilized as a universal method for detection of other chemical analytes with the replacement of the aptamer for recognition, and the nucleic acid LFS unit could also be a useful protocol for direct ssDNA analysis.

Accurate molecular identification of different meat adulterations without carryover contaminations on a microarray chip PCR-directed microfluidic lateral flow strip device.

Meat adulteration-based food fraud has recently become one of the global major economical, illegal, religious, and public health concerns. In this work, we developed a microarray chip polymerase chain reaction (PCR)-directed microfluidic lateral flow strip (LFS) device that facilitates the accurate and simultaneous identification of beef adulterated with chicken, duck, and pork, especially in processed beef products. To realize this goal, four pairs of amplification primers were designed and applied for specifically amplifying genomic DNA extracted from mixed meat powders in microarray chip. With the prominent advantage of this device lies in the flexible combination and integration of sample loading, detection, and reporting in microstructures, all the DNA amplicons can be individually visualized on the LFS unit, leading to the appearance of test lines (TC line, TD line, TP line, or TB line) as well as the control line (C line) for the species identification and quantification in beef products. Based on this new method, the adulterants were successfully distinguished and identified in mixtures down to 0.01% (wt.%) while the carryover aerogel contamination in routine molecular diagnostic laboratories was effectively avoided. The practicability, accuracy, and reliability of the device were further confirmed by using real-time PCR as a gold standard control on the successful identification of 50 processed ground meat samples sourced from local markets. The method and device proposed herein could be a useful tool for on-site identification of food authentication.

Curcumin inhibits Aspergillus flavus infection and aflatoxin production possibly by inducing ROS burst.

Aspergillus flavus contamination is common in various food and feed ingredients, and it poses to serious threats to human and animal health. Curcumin is a plant-derived polyphenol that exhibits antifungal activity. In this study, the antifungal effect of curcumin on A. flavus was evaluated, and the underlying mechanism was investigated. Curcumin effectively decreased aflatoxin B1 synthesis and suppressed A. flavus infection in peanut. Curcumin inhibited the mycelial growth and sporulation of A. flavus. Ergosterol biosynthesis in A. flavus was suppressed, and cell membrane permeability was enhanced. The pathogenicity of A. flavus was also reduced by curcumin treatment. Curcumin induced ROS burst in the hyphae of A. flavus, and those damages could be reversed by exogenous superoxide dismutase, suggesting that curcumin inhibited A. flavus possibly via inducing oxidative stress. These results indicate that curcumin has the potential to be used as a preservative to control A. flavus contamination in food and feedstuff.

Taking glucose as intermediate bridge-signal-molecule for on-site and convenient detection of ochratoxin A in rice with portable glucose meter.

On-site screening of biotoxins is of great importance for food safety. A new electrochemical-biosensing strategy was constructed for ochratoxin A (OTA) detection by direct using ready-made commercial portable-glucose-meter (PGM). Aptamer against OTA was adopted as the recognition probe and pre-immobilized onto the sensing interface. The complementary biotin-modified probe was further decorated by hybridization. Biotinylated invertase was further introduced onto the sensing system with streptavidin, which also acted as the signal amplification unit. The invertase, which was depended on the amount of OTA, produced the glucose from sucrose in the sensing solution. The glucose could be directly and conveniently measured with PGM. Quantitative analysis of OTA was achieved with a linear range from 0.5 ng/mL to 10 ng/mL and detection limit of 0.45 ng/mL. Of significance, it has been successfully applied for OTA analysis in rice with satisfied recoveries. This unique PGM-based electrochemical platform reveals prospective potential in food safety monitoring.

Accurate and Rapid Genetic Tracing the Authenticity of Floral Originated Honey with the Molecular Lateral Flow Strip.

Honey is a natural product and is heavily consumed for its well-known nutritional functions. Honeys with different floral origins possess distinctive flavors, tastes, functions and economic values. It is vital to establish an effective strategy for identifying the authenticity of honey. The intrinsic genetic materials of pollen were adopted as target analytes for the effective identification of honey with floral origins. With an optimized protocol for the rapid gene extraction from honey, target genetic templates were amplified on-site with a portable device. Conveniently, all on-site amplified functional products were easily judged by the designed lateral flow strip (LFS), which was defined as the molecular LFS in this research. Additionally, the entire on-site genetic authentication of honey was completed in less than 2 h by visual observation. Commercial honey products have been successfully identified with excellent accuracy. This low-cost, high-efficiency and easy-operational strategy will greatly benefit the quality guarantee of foods with specific functions and geographical markers.

Rapid and sensitive detection of Hg2+ with a SERS-enhanced lateral flow strip.

Mercury ions are some of the most toxic heavy metal ions widely distributed in the environment. Hg2+ cannot be degraded by microorganisms and can accumulate in the body through the food chain, posing a great threat to human health. Herein, a method combining surface-enhanced Raman scattering (SERS) with a lateral flow strip (LFS) (SERS-LFS) was developed for the rapid and quantitative analysis of Hg2+. The recognition of Hg2+ by the LFS depends on a specific T-Hg-T strategy. Rhodamine 6G (R6G), as a SERS reporter, was assembled on the surface of Au@Ag core-shell nanoparticles, which served as an effective SERS substrate on both the T and C lines of the LFS. Using this SERS-LFS, the presence of target Hg2+ could be measured through the appearance of an orange color on the T line of the LFS. Furthermore, with the direct measurement of SERS on the T lines of the LFS, the SERS signal could be collected even at a low concentration of Hg2+, at which point the signal on the T lines could not be observed. Based on the intensities of the characteristic peak at 1513 cm-1 of R6G collected on the T lines of the LFS, a linear relationship was obtained in the range of 0.01 nM to 1 nM, and the detection limit of the LFS was greatly improved by at least 20 times over the colorimetric results of the traditional LFS based on naked-eye observation. More importantly, this SERS-LFS did not affect the intrinsic simplicity of the LFS. This developed SERS-LFS holds great potential in practical routine screening in food safety and environmental monitoring.

Recent progress of personal glucose meters integrated methods in food safety hazards detection.

Development of personal glucose meters (PGMs) for blood glucose monitoring and management by the diabetic patients has been a long history since its first invention in 1968 and commercial application in 1975. The main reasons for its wide acceptance and popularity can be attributed mainly to the easy operation, test-to-result model, low cost, and small volume of sample required for blood glucose concentration test. During past decades, advances in analytical techniques have repurposed the use of PGMs into a general point-of-care testing platform for a variety of non-glucose targets, especially the food hazards. In this review, we summarized the recent published research using PGMs to detect the food safety hazards of mycotoxins, illegal additives, pathogen bacteria, and pesticide and veterinary drug residues detection with PGMs. The progress on PGM-based detection achieved in food safety have been carefully compared and analyzed. Furthermore, the current bottlenecks and challenges for practical applications of PGM for hazards detection in food safety have also been proposed.

Simultaneous and accurate screening of multiple genetically modified organism (GMO) components in food on the same test line of SERS-integrated lateral flow strip.

Herein, a surface-enhanced Raman scattering (SERS)-integrated LFS platform was developed for rapid and simultaneous screening of multiple genetically modified organism (GMO) components (promoter, codon, and terminator) in soybean. Research demonstrated that, on the same test line (T line) of single LFS, three different GMP components can be well distinguished with the help of three SERS nano tags. Good linear correlations between SERS signal and concentration of each GMO component were also obtained for quantitative analysis. Of greater importance, whether these multiple analytes coexisted or not, varied in the same concentration trend or not, these multiple GMP components can be rapidly (15 min) and accurately screened with satisfied sensitivity and specificity by decoding the signals on the same T line. We envision that this decoding platform can further improve the potential of LFS and SERS for practical applications and provide a promising alternative for multiple screening of GMO identification in food.

Continual and accurate home monitoring of uric acid in urine samples with uricase-packaged nanoflowers assisted portable electrochemical uricometer.

A convenient, fast and non-invasive portable electrochemical uricometer (PUM) assisted with the uricase-packaged nanoflowers (NFs) was constructed for continually and accurately monitoring of uric acid (UA) in urine samples at random intervals in just 20 s. Only a small amount of urine (50 µL) was needed for each test. Electrochemical deposition was adopted to modify gold nanoparticles (AuNPs) on screen-printed carbon electrodes (SPCE) and uricase-inorganic hybrid NFs (UOx-NFs) induced by calcium ions (Ca2+) were introduced for UA detection with expected specificity. Cyclic voltammetry (CV) (detection limit of 8.87 µM and liner range of 0-4 mM) and amperometry (detection limit of 0.82 µM and liner range of 0-5 mM) protocols were studied for UA detection, respectively. Finally, the uric acid in urine had be successfully continually monitored from volunteers with various dietary choosing, the results of which can be adopted as the effective evidence for uric acid control.

Facile design of multifunction-integrated linear oligonucleotide probe with multiplex amplification effect for label-free and highly sensitive GMO biosensing.

Well-defined structures and compositions of nucleic acids afford oligonucleotide probes with unique chemical properties and biological functions for various biosensing applications. Herein, a unique and special oligonucleotide probe, named multifunction-integrated linear oligonucleotide probe (MI-LOP), was facile designed and reported for label-free and turn-on fluorescent detection of the codon component of genetically modified organisms (GMOs). The MI-LOP contains four different functional regions including recognition of target, serving as polymerization template, and creating polymerization primer-linked G-quadruplex (PP-G-quadruplex). Without the aid of any other oligonucleotides, the introduction of target DNA can make each function of the MI-LOP executed one-by-one, during which the species of target DNA, target analogue, and PP-G-quadruplex can be cyclically utilized and in turn induce a multiplex signal amplification responsible for substantial collection of the G-quadruplex moieties under isothermal conditions. The stable G-quadruplexes can combine with N-methyl mesoporphyrin IX (NMM) and function as efficient fluorescence light-up probes, rapidly leading to a dramatic increase in the fluorescence intensity for the amplified detection of the target codon component. Our results strongly demonstrate that the developed MI-LOP with multiplex amplification effect confers the sensing strategy a high sensitivity and specificity for quantitative and qualitative detection of the target codon. And it has also been successfully applied for analyzing target codon in the complex extractions of soybean. The achievements highlight the significance of using oligonucleotide probes as promising analytical tools to promote the basic biochemical research and help in food and environmental analysis.

Time-resolved fluorescent lateral flow strip for easy and rapid quality control of edible oil.

Gutter oil is strictly prohibited from being reprocessed back to the catering and food industry. Extensive attention has been paid to rapid screening of gutter oil to guarantee the safety of edible oil. Capsaicin, a special component of condiments, has been adopted as the marker of gutter oil. The time-resolved fluorescent microspheres are utilized for labeling of antibody to capsaicin, which are further applied for the construction of fluorescent lateral-flow-strip (LFS). By simple extraction of capsaicin with ethanol (or liquor) from the edible oil, the capsaicin can be rapid determined with the fluorescent LFS in less than 10 min. As low as 20 ng/mL capsaicin can be visually judged and 2.3 ng/mL is achieved as the detection limit by ImageJ analysis. The illegal gutter oil is also well screened with this time-resolved LFS. This method can be a useful candidate for routine quality monitoring of edible oil and a powerful tool for self-inspection at home.

Simultaneous and accurate visual identification of chicken, duck and pork components with the molecular amplification integrated lateral flow strip.

We propose a visual strategy for simultaneous detection of multiple adulterated components in beef by integration of multiple polymerase chain reaction (mPCR) with the lateral flow strip (LFS). The primer sets for adulterated components are uniquely designed with different nucleic acid tags (NAT), enabling the amplicons with specific wobbled sequences at two opposite ends. The wobbled sequences will precisely hybridize with the pre-immobilized capture probes on T lines (T1, T2 and T3) and C line, contributing to the coloration of LFS. Taking advantages of extraordinary amplification efficiency of PCR and simplicity of LFS, common adulterated components including chicken, duck and pork can be easily detected with LOD as low as 0.01% (wt%), which is comparable to that of quantitative real-time polymerase chain reaction (qPCR) but with more simplified operations and reduced costs. The method can be extended to identification of other components by replacing the functional primer set. This method can be a useful candidate for meat quality control at the resource-limited setups.

Ingenious Electrochemiluminescence Bioaptasensor Based on Synergistic Effects and Enzyme-Driven Programmable 3D DNA Nanoflowers for Ultrasensitive Detection of Aflatoxin B1.

Aflatoxin B1 (AFB1), one of the most toxic mycotoxins, has undergone a wide range of studies over the years. The development of rapid, simple, and sensitive analytical methods remains a major challenge for the accurate detection of AFB1 in foodstuffs. In this study, we designed an enhanced and stable ingenious electrochemiluminescence bioaptasensor (IEC-BA) for ultrasensitive detection of AFB1 based on the synergistic effects and enzyme-driven programmable assembled 3D DNA nanoflowers (EPDNs). This synergistic effect was comprised by the competitive impact on auxiliary probes (AP) and the cutting effect of the Hae III. Compared to the traditional aptamer direct-competition method, the synergistic effects ensured that the aptamer was more efficiently and adequately competed away by the target. Also, the redundant double-stranded probes were removed, which greatly facilitates simple, quick, and sensitive detection of AFB1. Besides, a large chunk of positively charged Ru(II) complexes (Ru(bpy)32+) was accumulated by the utilization of EPDNs, which resulted in tremendous improvement of the sensitivity of the designed method. Thus, even in the presence of trace amounts of AFB1, a sharply visual electrochemiluminescent signal was generated. The proposed method can realize the quantification of AFB1 with a good linear range from 1 ppt (pg mL-1) to 5 ppb (ng mL-1) with a detection limit of 0.27 ppt. In addition, it can also be successfully applied for the analysis of AFB1 in a peanut and wheat, with total recoveries ranging from 93.7 to 106.6%. Furthermore, the IEC-BA also exhibited good selectivity, reproducibility, and stability, revealing prospective applications of food safety monitoring and environmental analysis.

Surface-Confined Building of Au@Pt-Centered and Multi-G-Quadruplex/Hemin Wire-Surrounded Electroactive Super-nanostructures for Ultrasensitive Monitoring of Morphine.

Overuse and abuse of morphine (MOP), one of the main components of pericarpium papaveris, have attracted increasing attention in the medical field owing to its pharmacological and toxicological activity. Herein, we proposed a new electrochemical nano-biosensor for MOP detection based on surface-confined building of Au@Pt-centered and multi-G-quadruplex/hemin wire-surrounded electroactive super-nanostructures. The center Au@Pt was flower-shaped and irregularly protruded, allowing substantial loading of multiple G-quadruplex wire/hemin complexes on its surface to accomplish the assembly of electroactive super-nanostructures. Interestingly, as the super-nanostructures were closely confined on the electrode surface, a significantly amplified electrochemical signal was thus obtained in the absence of MOP. In contrast, the introduction of target MOP can induce an intense competitive effect and strongly destroy the assembly process, resulting in the reduction of the electrochemical response that is correlated with the logarithmic concentration of MOP. Under optimal conditions, the electrochemical nano-biosensor is capable of highly sensitive detection of MOP in a dynamic concentration range from 1 ppt to 500 ppb. The limit of detection is achieved as low as 0.69 ppt, and the practical application was confirmed by examining MOP from chafing dish condiments. We expect the electrochemical platform utilizing this unique nanoarchitecture to provide rational guidelines to design high-performance analytical tools.

Prediction, evaluation, confirmation, and elimination of matrix effects for lateral flow test strip based rapid and on-site detection of aflatoxin B1 in tea soups.

Mycotoxin contaminations of tea have been considered serious problems. The presence of interfering substances presents enormous challenges to accurate detection of hazardous analytes in tea soups. In this work, we have carefully predicted, evaluated, and confirmed the matrix effects in tea that have an undesired influence on the detection of aflatoxin B1 (AFB1) in tea soups by lateral flow test strips (LFTS). After pretreatment of tea samples by simple dilution to change the acidic tea soups to alkaline environments, the matrix effects can be completely eliminated and the reliability of AFB1 analysis in tea soups can be effectively guaranteed. AFB1 contaminated samples of different tea soups can be accurately measured with detection limits down to 0.05 ppb. As the first pioneering report to study the matrix effects on AFB1 monitoring in tea soups by LFTS, we definitely expect this work to further widen the application of LFTS for hazard screening in food safety.

Ingenious Design of DNA Concatamers and G-Quadruplex Wires Assisted Assembly of Multibranched DNA Nanoarchitectures for Ultrasensitive Biosensing of miRNA.

Facile and efficient assembly of intelligent DNA nano-objects with the ability to exert robust microRNA determination is essential for DNA nanobiotechnology and basic biomedical study. Herein, we present a novel target-triggered DNA assembly pathway for the construction of multibranched DNA nanoarchitectures by the combination of DNA concatamers with G-quadruplex wires. The DNA concatamers acting as the main body structures were assembled by hybridization chain reaction (HCR), while the G-quadruplex wires acting as the branch structures were generated by terminal deoxynucleotidyl transferase (TdT)-promoted polymerization and G-quadruplex units (GUs) based self-assembly. With a copious number of G-quadruplex replicates collected on the electrode surface, the obtained multibranched DNA nanoarchitectures were able to bind with lots of hemin, which further led to a significantly amplified electrochemical sensing signal for ultrasensitive and selective detection of miRNA-21. The detection limit was achieved as low as 0.2 fM with a wide dynamic response ranging from 10 fM to 100 nM, which is much more powerful or at least comparable to most of the reported studies. Furthermore, the electrochemical biosensor offered an excellent specificity, and even the single-base mutation against the perfectly matched target miRNA can be easily distinguished easily. Furthermore, the real biological samples were also desirably analyzed, indicating that the proposed strategy is an ideal platform for the fabrication of versatile DNA nanobiosensors.

Copper-catalyzed reaction of ketenimine and in situ generated immonium ion: access to α,ß-unsaturated amidines.

A Cu-catalyzed three-component reaction of alkyne, azides (sulfonyl or phosphoryl azides), and N,N-dialkyloxyformamide dialkyl acetal via electrophilic addition of immonium ion to copper ketenimine is reported. This new protocol for the preparation of α,ß-unsaturated amidine derivatives appears to offer high yield, mild conditions, and wide substrate scope. The reaction might involve the processes of copper ketenimine intermediate formation, electrophilic addition, and isomerization.

[Simultaneous determination of 9 ultraviolet stabilizers in food plastic packaging materials by solid phase extraction-high performance liquid chromatography].

An effective high performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of 9 ultraviolet stabilizers in food plastic packaging materials. The food packaging samples were firstly extracted by methanol-ethyl acetate, and then purified by a C18 solid-phase extraction (SPE) column. The target compounds were separated on a ZORBAX SB-C18 column (250 mm x 4.6 mm, 5 microm) in gradient elution mode using methanol and water as mobile phases. The detection wavelength was at 310 nm. The linear plots of the nine ultraviolet stabilizers were obtained between 0.2 and 10 mg/L, with the correlation coefficients of above 0. 999 for the nine ultraviolet stabilizers. The limits of detection for this method were in the range from 0.05 to 0.1 mg/L. The recoveries spiked in commercial food plastic packaging materials were in the range of 70.2% - 89.0% with the relative standard deviations of 0.4% - 4.5%. The results indicated that the method is simple, accurate, and suitable for the simultaneous determination of the nine ultraviolet stabilizers in food plastic packaging materials.

Iron-promoted C-C bond cleavage of 1,3-diketones: a route to 1,2-diketones under mild reaction conditions.

A conceptual method for the preparation of 1,2-diketones is reported. The selective C-C bond cleavage of 1,3-diketones affords the 1,2-diketones in high yields under mild reaction conditions in air by the use of FeCl(3) as the catalyst and tert-butyl nitrite (TBN) as the oxidant without the use of solvent. The possible reaction mechanism is discussed. This protocol provides an expeditious route to the useful 1,2-diketones.