Sensitive colorimetric detection of Salmonella enteric serovar typhimurium based on a gold nanoparticle conjugated bifunctional oligonucleotide probe and aptamer

A Label-Free Colorimetric AuNP-Aptasensor for the Rapid Detection of Vibrio cholerae O139

Purpose

Waterborne pathogens pose a significant threat to public health, emphasizing the continuous necessity for advancing robust detection techniques, particularly in preventing outbreaks associated with these pathogens. This study focuses on cholera, an infectious disease caused by Vibrio cholerae, serogroups O1 and O139, often transmitted through contaminated water and food, raising significant public health concerns in areas with poor sanitation and limited access to clean water.

Methods

We developed a colorimetric biosensor using aptamer-functionalized gold nanoparticles to identify Vibrio cholerae O139 and address this issue. The detection mechanism relies on the color change of gold nanoparticles (AuNPs) from red to blue-purple induced by NaCl after the pathogen incubation and aptamer-target binding. Initial steps involved synthesizing and characterizing AuNPs, then exploring the impact of aptamer and NaCl concentrations on AuNP agglomeration. Optimization procedures for aptamer concentration and salt addition identified the optimal conditions for detection as 120 pM aptamers and 1 M NaCl.

Results

The aptasensor demonstrated a robust linear relationship, detecting V. cholerae concentrations from 103 to 108 CFU/mL, with a limit of detection (LOD) of 587 CFU/mL. Specificity tests and accurate sample analyses confirmed the efficiency of the AuNPs aptasensor, showcasing its reliability and speed compared to traditional culture examination methods. Moreover, we extended the aptasensor to a paper-based sensing platform with similar detection principles.

Conclusion

The change in color upon target binding was captured with a smartphone and analyzed using image processing software. The paper-based device detected the target in less than 2 min, demonstrating its convenience for on-field applications.

Bio-Receptors Functionalized Nanoparticles: A Resourceful Sensing and Colorimetric Detection Tool for Pathogenic Bacteria and Microbial Biomolecules

Pathogenic bacteria and several biomolecules produced by cells and living organisms are common biological components posing a harmful threat to global health. Several studies have devised methods for the detection of varying pathogenic bacteria and biomolecules in different settings such as food, water, soil, among others. Some of the detection studies highlighting target pathogenic bacteria and biomolecules, mechanisms of detection, colorimetric outputs, and detection limits have been summarized in this review. In the last 2 decades, studies have harnessed various nanotechnology-based methods for the detection of pathogenic bacteria and biomolecules with much attention on functionalization techniques. This review considers the detection mechanisms, colorimetric prowess of bio-receptors and compares the reported detection efficiency for some bio-receptor functionalized nanoparticles. Some studies reported visual, rapid, and high-intensity colorimetric detection of pathogenic bacteria and biomolecules at a very low concentration of the analyte. Other studies reported slight colorimetric detection only with a large concentration of an analyte. The effectiveness of bio-receptor functionalized nanoparticles as detection component varies depending on their selectivity, specificity, and the binding interaction exhibited by nanoparticles, bio-receptor, and analytes to form a bio-sensing complex. It is however important to note that the colorimetric properties of some bio-receptor functionalized nanoparticles have shown strong and brilliant potential for real-time and visual-aided diagnostic results, not only to assess food and water quality but also for environmental monitoring of pathogenic bacteria and a wide array of biomolecules.

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.

Functional Nanomaterials for the Detection and Control of Bacterial Infections

Infections with multidrug-resistant bacteria that are difficult to treat with commonly used antibiotics have spread globally, raising serious public health concerns. Conventional bacterial detection techniques are time-consuming, which may delay treatment for critically ill patients past the optimal time. There is an urgent need for rapid and sensitive diagnosis and effective treatments for multidrug-resistant pathogenic bacterial infections. Advances in nanotechnology have made it possible to design and build nanomaterials with therapeutic and diagnostic capabilities. Functional nanomaterials that can specifically interact with bacteria offer additional options for the diagnosis and treatment of infections due to their unique physical and chemical properties. Here, we summarize the recent advances related to the preparation of nanomaterials and their applications for the detection and treatment of bacterial infection. We pay particular attention to the toxicity of therapeutic nanoparticles based on both in vitro and in vivo assays. In addition, the major challenges that require further research and future perspectives are briefly discussed.

Noble Metal Nanoparticles Applications: Recent Trends in Food Control

Scientific research in the nanomaterials field is constantly evolving, making it possible to develop new materials and above all to find new applications. Therefore, nanoparticles (NPs) are suitable for different applications: nanomedicine, drug delivery, sensors, optoelectronics and food control. This review explores the recent trend in food control of using noble metallic nanoparticles as determination tools. Two major uses of NPs in food control have been found: the determination of contaminants and bioactive compounds. Applications were found for the determination of mycotoxins, pesticides, drug residues, allergens, probable carcinogenic compounds, bacteria, amino acids, gluten and antioxidants. The new developed methods are competitive for their use in food control, demonstrated by their validation and application to real samples.