Nuclear magnetic resonance biosensor based on streptavidin–biotin system and poly-l-lysine macromolecular targeted gadolinium probe for rapid detection of Salmonella in milk

NMR Immunosensor Based on a Targeted Gadolinium Nanoprobe for Detecting Salmonella in Milk

Detecting harmful pathogens in food is not only a crucial aspect of food quality management but also an effective way to ensure public health. In this paper, a complete nuclear magnetic resonance biosensor based on a novel gadolinium (Gd)-targeting molecular probe was developed for the detection of Salmonella in milk. First, streptavidin was conjugated to the activated macromolecular polyaspartic acid (PASP) via an amide reaction to generate SA-PASP. Subsequently, the strong chelating and adsorption properties of PASP toward the lanthanide metal gadolinium ions were exploited to generate the magnetic complex (SA-PASP-Gd). Finally, the magnetic complex was linked to biotinylated antibodies to obtain the bioprobe and achieve the capture of Salmonella. Under optimal experimental conditions, the sensor we have constructed can achieve a rapid detection of Salmonella within 1.5 h, with a detection limit of 7.1 × 103 cfu mL-1.

A fluorescent biosensor based on quantum dot-labeled streptavidin and poly-l-lysine for the rapid detection of Salmonella in milk

Salmonella, as a common foodborne pathogen in dairy products, poses a great threat to human health. We studied a new detection method based on quantum dots (QD). A fluorescent biosensor with multiple fluorescent signal amplification based on a streptavidin (SA) biotin system and the polyamino linear polymer poly-l-lysine (PLL) were established to detect Salmonella in milk. First, Salmonella was captured on a black 96-well plate with paired Salmonella mAb to form a double-antibody sandwich. Second, SA was immobilized on biotin-modified mAb by SA-biotin specific bond. Then, the biotin-modified polylysine (BT-PLL) was bound on SA and specifically bonded again through the SA-biotin system. Finally, water-soluble CdSe/ZnS QD-labeled SA was added to a black 96-well plate for covalent coupling with BT-PLL. The fluorescent signal was amplified in a dendritic manner by the layer-by-layer overlap of SA and biotin and the covalent coupling of biotinylated PLL. Under optimal conditions, the detection limit was 4.9 × 10³ cfu/mL in PBS. The detection limit was 10 times better than that of the conventional sandwich ELISA. In addition, the proposed biosensor was well specific and could be used for detecting Salmonella in milk samples.

Rapid detection of Salmonella in milk by a nuclear magnetic resonance biosensor based on the streptavidin-biotin system and O-carboxymethyl chitosan target gadolinium probe

Rapid and sensitive detection of foodborne pathogens is of great importance for food safety. Here, a set of nuclear magnetic resonance (NMR) biosensors based on a O-carboxymethyl chitosan target gadolinium (Gd) probe was developed to quickly detect Salmonella in milk by combining NMR technology and bioimmunotechnology with membrane filtration technology. First, O-carboxymethyl chitosan (O-CMC) was biotinylated to prepare biotinylated O-carboxymethyl chitosan (biotin-O-CMC) through amide reaction, and biotinylated magnetic complexes (biotin-O-CMC-Gd) were obtained by using O-CMC, which has strong chelating adsorption on Gd. The target probe was obtained by combining biotin-O-CMC-Gd with the biotinylated antibody (biotin-antibody) via streptavidin (SA) by introducing the SA-biotin system. Then, Salmonella was captured by the target probe through antigen-antibody interaction. Finally, NMR was used to measure the longitudinal relaxation time (T₁) of the filtrate collected by membrane filtration. This NMR biosensor with good specificity and high efficiency can detect Salmonella with the sensitivity of 1.8 × 10³ cfu/mL within 2 h; in addition, it can realize the detection of complex samples because of its strong anti-interference capability and may open up a new method for rapid detection of Salmonella, which has a great application potential.

Biosensing strategies for the electrochemical detection of viruses and viral diseases - A review

Viruses are the causing agents for many relevant diseases, including influenza, Ebola, HIV/AIDS, and COVID-19. Its rapid replication and high transmissibility can lead to serious consequences not only to the individual but also to collective health, causing deep economic impacts. In this scenario, diagnosis tools are of significant importance, allowing the rapid, precise, and low-cost testing of a substantial number of individuals. Currently, PCR-based techniques are the gold standard for the diagnosis of viral diseases. Although these allow the diagnosis of different illnesses with high precision, they still present significant drawbacks. Their main disadvantages include long periods for obtaining results and the need for specialized professionals and equipment, requiring the tests to be performed in research centers. In this scenario, biosensors have been presented as promising alternatives for the rapid, precise, low-cost, and on-site diagnosis of viral diseases. This critical review article describes the advancements achieved in the last five years regarding electrochemical biosensors for the diagnosis of viral infections. First, genosensors and aptasensors for the detection of virus and the diagnosis of viral diseases are presented in detail regarding probe immobilization approaches, detection methods (label-free and sandwich), and amplification strategies. Following, immunosensors are highlighted, including many different construction strategies such as label-free, sandwich, competitive, and lateral-flow assays. Then, biosensors for the detection of viral-diseases-related biomarkers are presented and discussed, as well as point of care systems and their advantages when compared to traditional techniques. Last, the difficulties of commercializing electrochemical devices are critically discussed in conjunction with future trends such as lab-on-a-chip and flexible sensors.

Biosensors for rapid detection of Salmonella in food: A review

Salmonella is one of the main causes of foodborne infectious diseases, posing a serious threat to public health. It can enter the food supply chain at various stages of production, processing, distribution, and marketing. High prevalence of Salmonella necessitates efficient and effective approaches for its identification, detection, and monitoring at an early stage. Because conventional methods based on plate counting and real-time polymerase chain reaction are time-consuming and laborious, novel rapid detection methods are urgently needed for in-field and on-line applications. Biosensors provide many advantages over conventional laboratory assays in terms of sensitivity, specificity, and accuracy, and show superiority in rapid response and potential portability. They are now recognized as promising alternative tools and one of the most on-site applicable and end user-accessible methods for rapid detection. In recent years, we have witnessed a flourishing of studies in the development of robust and elaborate biosensors for detection of Salmonella in food. This review aims to provide a comprehensive overview on Salmonella biosensors by highlighting different signal-transducing mechanisms (optical, electrochemical, piezoelectric, etc.) and critically analyzing its recent trends, particularly in combination with nanomaterials, microfluidics, portable instruments, and smartphones. Furthermore, current challenges are emphasized and future perspectives are discussed.

Magnetic Particles: Their Applications from Sample Preparations to Biosensing Platforms

The growing interest in magnetic materials as a universal tool has been shown by an increasing number of scientific publications regarding magnetic materials and its various applications. Substantial progress has been recently made on the synthesis of magnetic iron oxide particles in terms of size, chemical composition, and surface chemistry. In addition, surface layers of polymers, silica, biomolecules, etc., on magnetic particles, can be modified to obtain affinity to target molecules. The developed magnetic iron oxide particles have been significantly utilized for diagnostic applications, such as sample preparations and biosensing platforms, leading to the selectivity and sensitivity against target molecules and the ease of use in the sensing systems. For the process of sample preparations, the magnetic particles do assist in target isolation from biological environments, having non-specific molecules and undesired molecules. Moreover, the magnetic particles can be easily applied for various methods of biosensing devices, such as optical, electrochemical, and magnetic phenomena-based methods, and also any methods combined with microfluidic systems. Here we review the utilization of magnetic materials in the isolation/preconcentration of various molecules and cells, and their use in various techniques for diagnostic biosensors that may greatly contribute to future innovation in point-of-care and high-throughput automation systems.