Foodborne Pathogen Screening Using Magneto-fluorescent Nanosensor: Rapid Detection of <em>E. Coli</em> O157:H7

Abstract

Enterohemorrhagic Escherichia coli O157:H7 has been linked to both waterborne and foodborne illnesses, and remains a threat despite the food- and water-screening methods used currently. While conventional bacterial detection methods, such as polymerase chain reaction (PCR) and enzyme-linked immunosorbent assays (ELISA) can specifically detect pathogenic contaminants, they require extensive sample preparation and lengthy waiting periods. In addition, these practices demand sophisticated laboratory instruments and settings, and must be executed by trained professionals. Herein, a protocol is proposed for a simpler diagnostic technique that features the unique combination of magnetic and fluorescent parameters in a nanoparticle-based platform. The proposed multiparametric magneto-fluorescent nanosensors (MFnS) can detect E. coli O157:H7 contamination with as little as 1 colony-forming unit present in solution within less than 1 h. Furthermore, the ability of MFnS to remain highly functional in complex media such as milk and lake water has been verified. Additional specificity assays were also used to demonstrate the ability of MFnS to only detect the specific target bacteria, even in the presence of similar bacterial species. The pairing of magnetic and fluorescent modalities allows for the detection and quantification of pathogen contamination in a wide range of concentrations, exhibiting its high performance in both early- and late-stage contamination detection. The effectiveness, affordability, and portability of the MFnS make them an ideal candidate for point-of-care screening for bacterial contaminants in a wide range of settings, from aquatic reservoirs to commercially packaged foods.

Multimodal Magneto-Fluorescent Nanosensor for Rapid and Specific Detection of Blood-Borne Pathogens

“…Antibody-conjugating magnetic nanoparticles were synthesized following our previously reported protocol. − Briefly, the following solutions were prepared: (1) 4.0 mL of IONP-DiI/DiR-COOH (3.0 mmol) added to 1 mL of PBS (pH 7.4); (2) 5.0 mg of EDC in 250 μL of a MES buffer (0.1 M, pH 6.0); (3) 3.0 mg of NHS in 250 μL of a MES buffer (0.1 M, pH 6.0); (4) 5.0 μg of the corresponding antibodies IgG, the S. epidermidis mAb, or E. coli mAb in 225 μL of PBS (pH 7.4). After the preparation of solution 2, it was immediately added to solution 1, followed by the addition of solution 3, with brief mixing.…”

“…In recent years, the unique combination of nanotechnology and magnetic relaxation (MR) achieved through the fabrication of magnetic relaxation nanosensors (MRnSs) has been extensively used for the rapid detection of bacterial targets with greater sensitivity. − These MRnSs are synthesized by conjugating antibodies/affinity ligands on the surface of a superparamagnetic iron oxide nanoparticle (IONP). The underlying principle behind the detection lies in the switching of MRnSs between dispersed and clustered states due to interaction with the targeted bacterial contaminants, which results in a simultaneous change in the spin–spin relaxation time ( T 2 MR) of the water protons.…”

“…In likewise fashion, the use of magnetic nanoparticles in conjunction with fluorescence technology leads to significant improvements in the detection of pathogens at high concentrations, hence allowing a wide detection range. In our previous findings, the integration of MR technology with fluorescence allowed the rapid and sensitive detection of low and high concentrations of E. coli O157:H7 [1–100 colony-forming units (CFUs)/mL] in water and liquid food samples. , …”

Applications of Iron Oxide-Based Magnetic Nanoparticles in the Diagnosis and Treatment of Bacterial Infections

“…As a result of its low background, high sensitivity, high specificity, and the ease for quantitative analysis, fluorescent detection has been widely combined with MNPs for bacterial detection, since it is an emerging trend for the development of efficient biosensors for clinical use (Kwon et al, 2013; Tang et al, 2013; Chen et al, 2015c; Qin et al, 2016). MNPs with different fluorescent labels, such as Au (Kwon et al, 2013), rare earth-doped upconversion NPs (Qin et al, 2016), and the other labels (Jang et al, 2016; Shelby et al, 2017; Gontero et al, 2018) were conjugated with antibody or other target molecules for the detection of pathogenic bacteria. In these composite NPs, MNPs were used to capture and separate bacteria.…”

Electrochemical Detection of E. coli O157:H7 in Water after Electrocatalytic and Ultraviolet Treatments Using a Polyguanine-Labeled Secondary Bead Sensor

“…A drawback to all of these methods is that the samples must be sent to sterile laboratories containing expensive and bulky equipment, managed by skilled labor [ 7 ]. These methods are cost and time restrictive for most POU users who require expedient results in a few hours, instead of days [ 8 , 9 ]. People living in developing nations are less likely to have access to these resources [ 10 ].…”