Magnetic Fluorescent Quantum Dots Nanocomposites in Food Contaminants Analysis: Current Challenges and Opportunities

Ion coordination and chelation in Eu-MOFs matrices: Ultrafast fluorescence visual quantification monitoring of antibiotic residues

Rapid monitoring of trace antibiotics in the field in real time is essential for environment forewarning and human health. High sensitivity and real-time on-site quantitative monitoring of antibiotic residues can be accomplished by integrating portable sensors alongside fluorescent optics to construct an intelligent sensing platform that smoothly eliminates the instability of conventional detection methods. In this study, a ratiometric fluorescence sensor for the ultrasensitive detection of pefloxacin was built employing the photoinduced electron transfer (PET) mechanism from red Eu-MOFs to Mn2+-PEF complex. A visual color change results from the photoinduced electron transfer process from manganese ions to pefloxacin weakening the ligand metal charge transfer (LMCT) process in Eu-MOFs. This enables the ultrafast visible detection of pefloxacin and produces a transient shift in visual color with a detection limit as low as 15.4 nM. For the detection of pefloxacin in water, tomato, and raw pork samples, various sensing devices based on the developed fluorescent probes exhibit good practicability and accuracy. With the development of the ratiometric fluorescence sensing probe, it is now possible to quickly and quantitatively identify pefloxacin residues in the environment, offering a new method for ensuring the safety of food and people's health.

Label-free direct detection of melamine using functionalized gold nanoparticles-based dual-fluorescence colorimetric nanoswitch sensing platform

Developing a simple, economical, sensitive, and selective method for label-free direct detection analytes is attractive, especially the strategies that could achieve signal amplification without complicated operations. Herein, a dual-fluorescence colorimetric nanoswitch sensing platform for label-free direct melamine (MEL) detection was established. We first explored the relationship between MEL-induced aggregation of gold nanoparticles (AuNPs) and size and determined the optimal size to be 37 nm. Using surfactant Triton X-100 to modify AuNPs and clarify possible interaction mechanisms to improve detection performance. The dynamic changes of surface plasmon resonance absorption peaks in the dispersed and aggregated states of AuNPs were skillfully utilized to match the emission of multicolor gold nanoclusters to trigger the multi-inner filter effect. Accompanied by the addition of MEL-induced AuNPs to change from dispersed to aggregated state, the fluorescence of green-emitting and red-emitting gradually turned on and turned off, respectively. The fluorescence turn-on mode detection limit was 10 times higher than the colorimetric method and as low as 5.5 ng/mL; the detection took only 10 min. The sensor detected MEL in spiked milk samples with a good recovery in the range of 81.2-111.0 % with a coefficient of variation less than 11.4 % and achieved a good correlation with commercial kits. The proposed sensor integrates numerous merits of label-free, multi-signal readout, self-calibration, simple operations, and economical, which provides a promising tool for convenient on-site detection of MEL.

Recent Developments in Lateral Flow Assays for Salmonella Detection in Food Products: A Review

Salmonellosis is a disease transmitted by contaminated food and is one of the leading causes of infections worldwide, making the early detection of Salmonella of crucial importance for public health. However, current detection methods are laborious and time-consuming, thus impacting the entire food supply chain and leading to production losses and economic sanctions. To mitigate these issues, a number of different biosensors have been developed, including lateral flow assays (LFAs), which have emerged as valuable tools in pathogen detection due to their portability, ease of use, time efficiency, and cost effectiveness. The performance of LFAs has been considerably enhanced by the development of new nanomaterials over the years. In this review, we address the principles and formats of the assay and discuss future prospects and challenges with an emphasis on LFAs developed for the detection of different Salmonella serovars in food.

Molecular imprinting-based ratiometric fluorescence sensors for environmental and food analysis

Environmental protection and food safety are closely related to the healthy development of human society; there is an urgent need for relevant analytical methods to determine environmental pollutants and harmful substances in food. Molecular imprinting-based ratiometric fluorescence (MI-RFL) sensors, constructed by combining molecular imprinting recognition and ratiometric fluorescence detection, possess remarkable advantages such as high selectivity, anti-interference ability, high sensitivity, non-destruction and convenience, and have attracted increasing interest in the field of analytical determination. Herein, recent advances in MI-RFL sensors for environmental and food analysis are reviewed, aiming at new construction strategies and representative determination applications. Firstly, fluorescence sources and possible sensing principles are briefly outlined. Secondly, new imprinting techniques and dual/ternary-emission fluorescence types that improve sensing performances are highlighted. Thirdly, typical analytical applications of MI-RFL sensors in environmental and food samples are summarized. Lastly, the challenges and perspectives of the MI-RFL sensors are proposed, focusing on improving sensitivity/visualization and extending applications.

A Paper-Based Biomimetic Sensing Device for the Discrimination of Original and Fraudulent Cigarette Brands Using Mixtures of MoS2 Quantum Dots and Organic Dyes

In this study, we investigated the combined effects of MoS₂ QDs' catalytic properties and the colorimetric responses of organic reagents to create a sniffing device based on the sensor array concept of the mammalian olfactory system. The aim was to differentiate the volatile organic compounds (VOCs) present in cigarette smoke. The designed optical nose device was utilized for the classification of various cigarette VOCs. Unsupervised Principal Component Analysis (PCA) and supervised Linear Discriminant Analysis (LDA) methods were employed for data analysis. The LDA analysis showed promising results, with 100% accuracy in both training and cross-validation. To validate the sensor's performance, we assessed its ability to discriminate between five cigarette brands, achieving 100% accuracy in the training set and 82% in the cross-validation set. Additionally, we focused on studying four popular Iranian cigarette brands (Bahman Kootah, Omega, Montana Gold, and Williams), including fraudulent samples. Impressively, the developed sensor array achieved a perfect 100% accuracy in distinguishing these brands and detecting fraud. We further analyzed a total of 126 cigarette samples, including both original and fraudulent ones, using LDA with a matrix size of (126 × 27). The resulting LDA model demonstrated an accuracy of 98%. Our proposed analytical procedure is characterized by its efficiency, affordability, user-friendliness, and reliability. The selectivity exhibited by the developed sensor array positions it as a valuable tool for differentiating between original and counterfeit cigarettes, thus aiding in border control efforts worldwide.

Progress in Fluorescence Biosensing and Food Safety towards Point-of-Detection (PoD) System

The detection of pathogens in food substances is of crucial concern for public health and for the safety of the natural environment. Nanomaterials, with their high sensitivity and selectivity have an edge over conventional organic dyes in fluorescent-based detection methods. Advances in microfluidic technology in biosensors have taken place to meet the user criteria of sensitive, inexpensive, user-friendly, and quick detection. In this review, we have summarized the use of fluorescence-based nanomaterials and the latest research approaches towards integrated biosensors, including microsystems containing fluorescence-based detection, various model systems with nano materials, DNA probes, and antibodies. Paper-based lateral-flow test strips and microchips as well as the most-used trapping components are also reviewed, and the possibility of their performance in portable devices evaluated. We also present a current market-available portable system which was developed for food screening and highlight the future direction for the development of fluorescence-based systems for on-site detection and stratification of common foodborne pathogens.

Current Progress of Ratiometric Fluorescence Sensors Based on Carbon Dots in Foodborne Contaminant Detection

Carbon dots (CDs) are widely used in the detection of foodborne contaminants because of their biocompatibility, photoluminescence stability, and ease of chemical modification. In order to solve the interference problem of complexity in food matrices, the development of ratiometric fluorescence sensors shows great prospects. In this review, the progress of ratiometric fluorescence sensors based on CDs in foodborne contaminant detection in recent years will be summarized, focusing on the functionalized modification of CDs, the fluorescence sensing mechanism, the types of ratiometric fluorescence sensors, and the application of portable devices. In addition, the outlook on the development of the field will be presented, with the development of smartphone applications and related software helping to better enable the on-site detection of foodborne contaminants to ensure food safety and human health.