Aptamer-Based Fluorescent Biosensors for Kanamycin Detection in Food Systems: Design Strategies, Sensing Mechanisms, and Practical Applications

Paper-Based Biosensor Using Dual-Recognition Molecules for Detection of Staphylococcus aureus in Milk

Staphylococcus aureus (S. aureus) is a common foodborne pathogen that can cause the severe contamination of dairy products. Therefore, there is an urgent need for rapid detection methods. In this study, a paper-based biosensor integrating a dual-recognition strategy using aptamers and antibodies was developed for the sensitive, rapid, and on-site detection of S. aureus in complex milk matrices. The biosensor combines a milk matrix-adapted aptamer with polyclonal antibodies (pAbs) and utilizes colloidal gold nanoparticles (AuNPs) as visual signal reporters. Using a SELEX process tailored to the milk matrix, the high-affinity aptamer SA2-1 was selected to specifically bind S. aureus, while pAbs enabled multi-epitope capture on the paper substrate. The aptamer–AuNP conjugates generated visual signals, achieving a detection limit of 102 CFU/mL within 15 min without an instrument. This dual-recognition strategy synergistically enhances both sensitivity and specificity, offering a cost-effective solution for dairy safety monitoring.

Recent Progress in Nanoparticle-Based Biosensors for Monitoring Shigella spp. in Food Safety: A Critical Review

Shigella is a foodborne bacterial pathogen with a low infectious dose and significant public health impact. Culture-based and molecular techniques provide reliable identification but are time-consuming. Nanoparticle-based biosensors offer sensitive, selective, and compact alternatives. Recent advances in nanoparticle-based biosensors for Shigella spp. (S. flexneri, S. sonnei, S. dysenteriae, and S. boydii) detection have been reviewed in terms of signal amplification, biorecognition, biological targets, sensor types, and performance in real food matrices. Detection strategies rely on gene-level and whole-cell recognition. Targeting virulence genes, invasion plasmid antigen H (ipaH), provides stable genus-level identification, whereas whole-cell recognition facilitates rapid detection without extensive sample preparation. Optical biosensors, including fluorescence-based methods, surface-enhanced Raman spectroscopy (SERS), and localized surface plasmon resonance (LSPR), achieve low detection limits with strong tolerance to complex food matrices. Electrochemical biosensors offer operational simplicity, portability, and suitability for food screening. Lateral flow and hybrid systems provide rapid detection through simplified assay formats and visual readout, with performance influenced by the balance between speed and sensitivity. Validation in real food matrices shows acceptable recoveries, minimal cross-reactivity, and agreement with reference methods. This overview provides a design-oriented framework for nanoparticle-based biosensor selection in food safety by integrating nanomaterial function, biosensor design, and performance characteristics.

Computer-assisted hapten design enables aptamer and hybrid aptamer-antibody rapid assays for detection of citrinin in red yeast rice.

Citrinin (CTN), a nephrotoxic and hepatotoxic mycotoxin frequently found in red yeast rice, requires rapid and reliable detection. Here, six CTN haptens were rationally designed using computational chemistry, and two optimal structures were selected for generating CTN-specific aptamers via systematic evolution of ligands by exponential enrichment (SELEX). Based on these aptamers (Apts), four analytical platforms were developed, including enzyme-linked aptamer sorbent assay (ELASA), aptamer-based lateral flow strip (Apt-LFS), hybrid enzyme-linked aptamer-antibody assay (ELAAA), and hybrid lateral flow strip (Hybrid-LFS). The limits of detection were 1.9, 500, 10, and 250 ng/mL, respectively. In spiked red yeast rice samples, ELASA and ELAAA showed average recoveries of 102% and 104%. Analysis of 15 commercial samples showed excellent consistency with HPLC, while Apt-LFS and Hybrid-LFS identified four positive samples according to Taiwan Food and Drug Administration (TFDA) limits. This study provides a sensitive and practical strategy for CTN monitoring in complex food matrices.

Dual-ligand quantum dot biosensor combining IgY antibodies and DNA aptamers for rapid, on-site detection of staphylococcal enterotoxin A (SEA) in food matrices.

Aptamer–gold nanoparticle-based lab-in-a-tube colorimetric detection of malathion: evaluation with classical and digital readout techniques

Colorimetric biosensing devices represent an important class of point-of-care (POC) diagnostics due to their ability to provide visible test outputs, their ease of integration with smartphone-based sensing, and their portability for field testing. In the context of agrifood safety, there is a growing need for portable, robust, and cost-effective detection devices. Pesticide residues can be present in a wide range of environmental and food samples, from water resources to fruits and vegetables, resulting in an increasing global demand for on-site testing. Colorimetric assays, when combined with smartphone-based sensing, can effectively address these needs. In this work, the aggregation-induced color change response of aptamer–gold nanoparticle conjugates was exploited to design a lab-in-a-tube colorimetric assay for the detection of malathion. The performance of the assay was evaluated using both a conventional spectrophotometric method as a laboratory-based reference and a smartphone-based readout supported by color intensity analysis as a portable detection approach. Color responses were quantified using both a mobile application and computer software across different color channels. The smartphone-based readout yielded a limit of detection (LOD) of 5.14 mg/mL and a linear detection range of 0.02–100 mg/mL with a correlation coefficient (R2) of 0.9981 for the mobile application, while the computer software-based analysis exhibited an LOD of 0.88 mg/mL, a linear range of 0.02–50 mg/mL, and an R2 of 0.9789. In comparison, the spectrophotometric method showed an LOD of 1.67 mg/mL, a linear range of 0.02–100 mg/mL, and an R2 of 0.9948, confirming the reliability of the smartphone-based approaches. The results demonstrate that the colorimetric assay developed can be successfully integrated with smartphones for field-testing applications, while providing a competitive LOD comparable to laboratory-based methods.

G-quadruplex-based fluorescent sensing platform for thiamethoxam detection: integrating multiple signal amplification strategies.

Thiamethoxam, a widely utilized neonicotinoid insecticide, has been extensively applied in agricultural practices, leading to various adverse effects on human health, such as neurotoxicity, developmental issues, and endocrine disruption. Therefore, establishing a comprehensive and standardized surveillance framework for the quantitative determination of thiamethoxam residues in environmental compartments and food matrices is critical for mitigating its chronic toxicological risks to human health. We developed a biosensor for thiamethoxam detection, which leverages the target-induced formation of G-quadruplexes and subsequent Thioflavin T fluorescence enhancement based on Exonuclease III-driven shear amplification and the hybridization chain reaction. Under optimized conditions, this biosensor exhibited a detection range from 10 pg mL-1 to 1 µg mL-1 and a detection limit of 8.7 pg mL-1. Furthermore, the successful detection of thiamethoxam in real samples confirms the biosensor's practical applicability and reliability.