An emerging assay for rapid diagnosis of live Salmonella Typhimurium by exploiting aqueous/liquid crystal interface.

The rapid and accurate identification of live pathogens with high proliferative ability is in great demand to mitigate foodborne infection outbreaks. Herein, we have developed an ultrasensitive image-based aptasensing array to directly detect live Salmonella typhimurium (S.T) cells. This method relies on the long-range orientation of surfactant-decorated liquid crystals (LCs) and the superiority of aptamers (aptST). The self-assembling of hydrophobic surfactant tails leads to a perpendicular/vertical ordered film at the aqueous/LC interface and signal-off response. The addition of aptST perturbed LCs' ordering into a planar/tilted state at the aqueous phase due to electrostatic interactions between the surfactant with the aptST, and a signal-on response. Following the conformational switch of aptST in the presence of live S. typhimurium, a relative reversing signal-off response was observed upon the target concentration. This aptasensor could promptly confirm the presence of S. typhimurium without intricate DNA-extraction or pre-enrichment stats over a linear range of 1-1.1 × 106 CFU/mL and a detection limit of 1.2 CFU/mL within ∼30 min. These results were successfully validated using molecular and culture-based methods in spiked-milk samples, with a 92.61-104.61 % recovery value. Meanwhile, the flexibility of this portable sensing platform allows for its development and adoption for the precise detection of various pathogens in food and the environment.

Smart nano-inks based on natural food colorant for screen-printing of dynamic shelf life of shrimp.

Intelligent packaging embedded with food freshness indicators can monitor food quality and be deployed for food safety and cutting food waste. The innovative nano-inks for dynamic shelf-life printing based on natural food colorant with application in real-time monitoring of shrimp freshness were prepared. Co-assembly of saffron petal anthocyanin (SPA) with hydrophobic curcumin (Cur) into chitin nano-scaffold (particle sizes around 26 ± 8 nm) could deliver hindering SPA leaching, confirmed by FT-IR, FE-SEM, AFM, and color stability test. The best response to pH-sensitivity was found in a ratio of (1:4) Cur/SPA (30% (v/w) in ChNFs that was correlated with the chemical and microbial changes of shrimp during shrimp freshness. However, smart screen-printed inks signified higher responsiveness to pH changes than FFI films. Therefore, smart-printed indicators introduced the excellent potential for a short response time, easy, cost-effective, eco-friendly, co-assembly, great color stabilities, and lifetime for nondestructively freshness monitoring foods and supplements.

Polyphenol-loaded bacterial cellulose nanofiber as a green indicator for fish spoilage.

Seafood products as a source of vitamins, minerals, and polyunsaturated fatty acids represent an important component of the human diet. However, they are susceptible to spoilage even under appropriate storage conditions, making it indispensable to develop freshness indicators. In this study, we introduce a green user-friendly pH indicator film for the naked-eye monitoring of fish spoilage. The pH indicator was prepared by successful loading of a mixture of anthocyanin and curcumin on bacterial cellulose (BC) nanofiber substrate. BC nanofiber with the advantages of biocompatibility, biodegradability, high purity, and superior mechanical strength was promising for generating pH-sensing arrays. The Fourier transform infrared (FT-IR) analysis proved the incorporation of anthocyanin and curcumin into the BC skeleton. Besides, the scanning electron microscopy (SEM) results clarified the morphology of the modified film by anthocyanin and curcumin. The pH indicator film was still stable after preserving for 60 days at different temperatures. The curcumin-anthocyanin loaded nanofiber indicated a distinct color change after spoilage by its exposure to fish meat in a transparent plastic package. Hence, the modified film by the anthocyanin-curcumin mixture is potent for the naked-eye monitoring of meat spoilage.

Recent Advances in Aptasensing Strategies for Monitoring Phycotoxins: Promising for Food Safety.

Phycotoxins or marine toxins cause massive harm to humans, livestock, and pets. Current strategies based on ordinary methods are long time-wise and require expert operators, and are not reliable for on-site and real-time use. Therefore, it is urgent to exploit new detection methods for marine toxins with high sensitivity and specificity, low detection limits, convenience, and high efficiency. Conversely, biosensors can distinguish poisons with less response time and higher selectivity than the common strategies. Aptamer-based biosensors (aptasensors) are potent for environmental monitoring, especially for on-site and real-time determination of marine toxins and freshwater microorganisms, and with a degree of superiority over other biosensors, making them worth considering. This article reviews the designed aptasensors based on the different strategies for detecting the various phycotoxins.