Ultrasensitive Ti3C2Tx@Pt-Based Immunochromatography with Catalytic Amplification and a Dual Signal for the Detection of Chloramphenicol in Animal-Derived Foods.

Herein, a catalytic amplification enhanced dual-signal immunochromatographic assay (ICA) based on Pt nanoparticles (Pt NPs) modified with Ti3C2Tx MXene (Ti3C2Tx@Pt) was first developed for chloramphenicol (CAP) in animal-derived foods. Due to the large specific surface area and abundant active sites of Ti3C2Tx@Pt, they can be loaded with hundreds of Pt NPs to enhance their catalytic activity, resulting in a significant increase in the detection sensitivity; the sensitivity was up to 50-fold more sensitive than the reported ICA for CAP. The LODs of the developed method for milk/chicken/fish were 0.01 µg/kg, the LOQs were 0.03 µg/kg and the recovery rates were 80.5-117.0%, 87.2-118.1% and 92.7-117.9%, with corresponding variations ranging from 3.1 to 9.6%, 6.0 to 12.7% and 6.0 to 13.6%, respectively. The linear range was 0.0125-1.0 µg/kg. The results of the LC-MS/MS confirmation test on 30 real samples had a good correlation with that of our established method (R2 > 0.98), indicating the practical reliability of the established method. The above results indicated that an ICA based on the Ti3C2Tx@Pt nanozyme has excellent potential as a food safety detection tool.

High-Density Au Anchored to Ti3C2-Based Colorimetric-Fluorescence Dual-Mode Lateral Flow Immunoassay for All-Domain-Enhanced Performance and Signal Intercalibration.

In this work, a novel MXene-Au nanoparticle (Ti3C2@Au) was synthesized with a high molar extinction coefficient, strong fluorescence quenching ability, ultrahigh antibody affinity, high stability, and good dispersibility, and it was used to develop a colorimetric-fluorescence dual-mode lateral flow immunoassay (LFIA). The detection limits of this method for the detection of dexamethasone in milk, beef, and pork were 0.0018, 0.12, and 0.084 µg/kg in the "turn-off" mode (colorimetric signal), and 0.0013, 0.080, and 0.070 µg/kg in the "turn-on" mode (fluorescent signal), respectively, which was up to 231-fold more sensitive compared with that of the reported LFIAs. The recovery rates ranged from 81.1-113.7%, and 89.2-115.4%, with the coefficients of variation ranging from 1.4-15.0%, and 1.9-14.8%, respectively. The results of the LC-MS/MS confirmation test on 30 real samples had a good correlation with that of our established method (R2 > 0.97). This work not only developed novel nanocarriers for antibody-based LFIA but also ensured high-performance detection.

Formation and Detection of Gizzerosine in Animal Feed Matrices: Progress and Perspectives.

Gizzerosine is responsible for gizzard erosion and black vomit, owing to excessive gastric acid secretion in poultry. It is a biogenic amine that forms during feed processing. Gizzerosine, a derivative of histamine, is a serious threat to animal feed safety and poultry production because it is more potent after ingestion and more harmful to poultry than histamine. The difficulty of obtaining gizzerosine and the lack of simple, rapid, and sensitive in vitro detection techniques have hindered studies on the effects of gizzerosine on gizzard health and poultry production. In this review, we evaluated the natural formation and the chemical synthesis methods of gizzerosine and introduced seven detection methods and their principles for analyzing gizzerosine. This review summarizes the issues of gizzerosine research and suggests methods for the future development of gizzerosine detection methods.

A sensitive and quantitative immunochromatographic assay for simultaneous detection of three stimulant laxatives in slimming food.

Bisacodyl, sodium picosulfate and their metabolite bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM) are clinically used to treat constipation. In this study, with the rational hapten design, a broad-specific and highly sensitive monoclonal antibody (mAb) was obtained with half of inhibitory concentrations of 0.16, 0.18 and 0.65 ng/mL for bisacodyl, sodium picosulfate and BHPM, respectively. Based on this mAb, a rapid and sensitive lateral flow immunochromatographic assay toward bisacodyl, sodium picosulfate and BHPM in slimming foods was developed. This method can qualitatively and quantitatively screen three stimulant laxatives with cut-off values of 3-6 ng/mL by naked eye and quantitative detection limits of 0.14-0.41 ng/mL by reader. The acceptable recoveries of spiked samples (78.00 %-120.12 %) and consistent results with liquid chromatography with tandem mass spectrometry (LC-MS/MS) in real sample detection confirmed the accuracy of the method. The established method provides a technique for multiplex, sensitive, fast, and on-site detection of three stimulant laxatives in slimming food.

[Determination of nine beta-agonist residues in pig tissues by liquid chromatography-tandem mass spectrometry combining with library search].

A new method has been developed using a hybrid triple-quadrupole linear ion trap (QTrap) mass spectrometer for the fast detection and identification of nine beta-agonists, clenbuterol, salbutamol, ractopamine, ritodrine, terbutaline, isoxsuprine, tulobuterol, cimaterol and bambuterol, in one single liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The homogenized tissue samples were purified with liquid-liquid extraction after enzymatic hydrolysis by P-glucuronidase/aryl sulfatase. After gradient elution separation on C(18) LC column using acetonitrile and formic acid aqueous solution as the mobile phases, a multiple reaction monitoring (MRM) scan as survey scan and an enhanced product ion (EPI) scan as dependent scan were performed in an information dependent acquisition (IDA) experiment. Finally, the identification of the drugs was carried out by library search with a newly developed MS/MS library based on EPI spectra at three different collision energies in positive mode. The analytical method in the present study was well validated and good results were obtained with respect to precision, repeatability and spiked recovery. The limits of detection of residues were 0.1 -0.2 micro g/kg for beta-agonists, and with a linear range from 0.1 to 50.0 micro g/L. Three concentration levels of 0. 5, 1. 0 and 5. 0 pg/kg were spiked in pig tissues, and the overall recoveries were between 72.0% and 95.1% with the relative standard deviations (RSDs) between 3. 1% and 12.1%. The real sample test showed that this method could be used for sensitive and accurate determination of beta-agonist residues in pig tissue

[Determination of melamine residue in feeds by ultra performance liquid chromatography coupled with electrospray tandem mass spectrometry].

A method for fast determination melamine residue in feeds was established. An ultra performance liquid chromatography coupled with electrospray ionization quadrupole tandem mass spectrometry (UPLC-ESI-MS/MS) was used. The residue was quantified with multiple reaction monitoring (MRM) mode. The method was validated and good results were obtained with respect to precision, repeatability and spiked recovery. The limit of detection was 10 microg/kg for melamine, and the linear range was from 10 to 5 000 1g/kg. The average recoveries were between 83% and 94% in the spiked range of 10 - 100 microg/kg, and the relative standard deviations (RSDs) were between 4.2% and 6.5%. The method has good repeatability and high sensitivity, and can be applied for the determination of melamine residue in feeds.