Shuyuan Du

A composite nanomaterial of Prussian blue@gold nanoparticles (PB@Au) with catalytic and photothermal properties was proposed, which combined with anti-matrix interference aptamers to achieve robust specificity and sensitivity in the detection of Salmonella typhimurium (S. typhimurium). The detection probe, PB@Au-Aptamer (PB@Au-Apt), was designed to exhibit high specificity for the target and catalyze the signal generation to produce a color change, thereby enabling rapid detection. Additionally, the excellent photothermal performance of the PB@Au catalytic system was utilized for multimodal sensitive detection in the multimodal nanoenzyme-linked aptamer assay. Moreover, the utilization of both catalytic and photothermal dual-mode detection was mutually verified to enhance detection accuracy. Under optimal conditions, the detection of S. typhimurium in a sample can be completed in 2 h. The developed assay exhibited exceptional specificity in detecting S. typhimurium, with an impressive detection limit down to 23 CFU·mL⁻¹. Furthermore, the assay exhibited excellent repeatability and stability. Real sample analyses have proven the high reliability and practicality of this assay, highlighting its significant potential for applications in food safety testing.

A sensitive, accurate, and rapid multimode dot-filtration immunoassay (MDFIA) was established for the detection of Salmonella typhimurium using the intrinsic color, catalytic property, and photothermal effect of magnetic molybdenum disulphide (MoS₂@Fe₃O₄). The critical performance parameters of MDFIA were optimized in detail. The sensitivity of MDFIA can be improved by the catalytic color development and photothermal conversion of MoS₂@Fe₃O₄ with a limit of detection (LOD) of 10¹ CFU·mL⁻¹, which is an order of magnitude lower than direct visual detection (10² CFU·mL⁻¹). Besides, the magnetic property of MoS₂@Fe₃O₄ was used for the rapid enrichment and separation of the target allowing detection of trace concentrations of Salmonella typhimurium. The selectivity and applicability of the MDFIA were verified in spiked samples, indicating that the established assay may have bright application prospects for the detection and control of foodborne pathogens. Graphical abstract A multimode dot-filtration immunoassay was constructed for Salmonella typhimurium rapid detection based on the peroxidase-like activity, magnetic property, and photothermal effect of MoS₂@Fe₃O₄.

The residue of estrogenic-disrupting compounds (EDCs) that are secreted by cows, added as drugs, and present in the feed may exist in dairy products. A gold nanoparticles (AuNPs)-estrogen receptor (ER) cocktail colorimetric assay equipped with ER cocktail solid phase extraction (SPE) was established to screen EDCs. Nine EDCs with high, moderate, and low estrogenic activity were selected to be the representative targets. The recognition range of the colorimetric assay combined with the ER cocktail SPE was wider than that of a single ERα or ERβ. The lowest detection limit of the established assay was about 10⁻⁹ mg·mL⁻¹. The detection limits of estrone, bisphenol A, and bisphenol B were about one order of magnitude lower than the method based on a single ER. The recoveries of the spiked nine EDCs were between 80.0% and 110.0%, and daidzein was identified in the dairy product. The developed method has potential application prospects in food safety and environmental monitoring.

Salmonella contamination in food production and processing is a serious threat to consumer health. More and more rapid detection methods have been proposed to compensate for the inefficiency of traditional bacterial cultures to suppress the high prevalence of Salmonella more efficiently. The contamination of Salmonella in foods can be identified by recognition elements and screened using rapid detection methods with different measurable signals (optical, electrical, etc.). Therefore, the different signal transduction mechanisms and Salmonella recognition elements are the key of the sensitivity, accuracy and specificity for the rapid detection methods. In this review, the bioreceptors for Salmonella were firstly summarized and described, then the current promising Salmonella rapid detection methods in foodstuffs with different signal transduction were objectively summarized and evaluated. Moreover, the challenges faced by these methods in practical monitoring and the development prospect were also emphasized to shed light on a new perspective for the Salmonella rapid detection methods applications.

A wide variety of biotic and abiotic stresses continually attack plants and animals, which adversely affect their growth, development, reproduction, and yield realization. To survive under stress conditions, highly sophisticated and efficient tolerance mechanisms have been evolved to adapt to stresses, which consist of the variation of effector molecules playing vital roles in physiological regulation. The development of a sensitive, facile, and rapid analytical methods for stress factors and effector molecules detection is significant for gaining deeper insight into the tolerance mechanisms. As a nondestructive analysis technique, surface-enhanced Raman spectroscopy (SERS) has unique advantages regarding its biosensing applications. It not only provides specific fingerprint spectra of the target molecules, conformation, and structure, but also has universal capacity for simultaneous detection and imaging of targets owing to the narrow width of the Raman vibrational bands. Herein, recent progress on biotic and abiotic stresses, tolerance mechanisms and effector molecules is summarized. Moreover, the development and promising future trends of SERS detection for stress-related substances combined with nanomaterials as substrates and SERS tags are discussed. This comprehensive and critical review might shed light on a new perspective for SERS applications.

In this paper, a novel amperometric immunosensor for the determination of carbofuran based on gold nanoparticles (GNPs), magnetic Fe₃O₄ nanoparticles-functionalized multiwalled carbon nanotubes-chitosan (Fe₃O₄-FCNTs-CS), and bovine serum albumin (BSA) composite film was proposed. First, GNPs were immobilized onto the glassy carbon electrode (GCE) surface, and then the magnetic Fe₃O₄ nanoparticles mixed with chitosan-functionalized multiwall carbon nanotubes (CS-FCNTs) homogeneous composite (CS-FCNTs-Fe₃O₄) was immobilized onto the GNPs layer by electrostatic interactions between amino groups of CS and GNPs. Because chitosan (CS) contains many amino groups, it can absorb more antibodies. FCNTs have high surface area, high electrical conductivity, and it can enhance the electron transfer rate; Magnetite (Fe₃O₄) nanoparticles can provide a favorable microenvironment for biomolecules immobilization due to their good biocompatibility, strong superparamagnetic property, and low toxicity; and GNPs possess high surface-to-volume reaction, stability, and high conductivity. Gold Nanoparticles/Fe₃O₄-FCNTs-CS composite film was constructed onto the GCE surface, which had significant synergistic effects toward immunoreaction signal amplification. The stepwise assembly process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Under the optimal conditions, the current response was proportional to the concentration of carbofuran ranging from 1.0 ng/mL to 100.0 ng/mL and from 100.0 ng/mL to 200 µg/mL with the detection limit 0.032 ng/mL. The proposed immunosensor exhibited good accuracy, high sensitivity, and stability, and it can be used for detection of carbofuran pesticide.