Abstract
Optical biosensors for rapid detection of significant foodborne pathogens are steadily gaining popularity due to its simplicity and sensitivity. While nanomaterials such as gold nanoparticles (AuNPs) are commonly used as signal amplifiers for optical biosensors, AuNPs can also be utilized as a robust biosensing platform. Many reported optical biosensors were designed for individual pathogen detection in a single assay and have high detection limit (DL). Salmonella spp. is one of the major causative agents of foodborne sickness, hospitalization and deaths. Unfortunately, there are around 2,000 serotypes of Salmonella worldwide, and rapid and simultaneous detection of multiple strains in a single assay is lacking. In this study, a comprehensive and highly sensitive simultaneous colorimetric detection of nineteen (19) environmental and outbreak Salmonella spp. strains was achieved by a novel optical biosensing platform using oligonucleotide-functionalized AuNPs. A pair of newly designed single stranded oligonucleotides (30-mer) was displayed onto the surface of AuNPs (13 nm) as detection probes to hybridize with a conserved genomic region (192-bases) of ttrRSBCA found on a broad range of Salmonella spp. strains. The sandwich hybridization (30 min, 55°C) resulted in a structural formation of highly stable oligonucleotide/AuNPs-DNA complexes which remained undisturbed even after subjecting to an increased salt concentration (2 M, final), thus allowing a direct discrimination via color change of target (red color) from non-target (purplish-blue color) reaction mixtures by direct observation using the naked eye. In food matrices (blueberries and chicken meat), nineteen different Salmonella spp. strains were concentrated using immunomagnetic separation and then simultaneously detected in a 96-well microplate by oligonucleotide-functionalized AuNPs after DNA preparation. Successful oligonucleotide/AuNPs-DNA hybridization was confirmed by gel electrophoresis while AuNPs aggregation in non-target and control reaction mixtures was verified by both spectrophotometric analysis and TEM images. Results showed that the optical AuNP biosensing platform can simultaneously screen nineteen (19) viable Salmonella spp. strains tested with 100% specificity and a superior detection limit of <10 CFU/mL or g for both pure culture and complex matrices setups. The highly sensitive colorimetric detection system can significantly improve the screening and detection of viable Salmonella spp. strains present in complex food and environmental matrices, therefore reducing the risks of contamination and incidence of foodborne diseases.
Highlights
Nanomaterials are commonly incorporated in the development of optical biosensors to enhance its sensitivity (Pérez-López and Merkoçi, 2011)
We developed a novel approach for simultaneous optical detection of various Salmonella spp. strains in contaminated complex matrices by utilizing oligonucleotide-functionalized AuNPs as a sensitive optical biosensing platform in combination with an efficient sample pooling and immunomagnetic separation (IMS) system that ensure detection of viable cells
The solution shifted from the initial bluish-gray color to purplish until it completely turned to ruby red solution which was one of the primary attributes of spherical AuNPs within 5–15 nm diameter range (Wuithschick et al, 2015)
Summary
Nanomaterials are commonly incorporated in the development of optical biosensors to enhance its sensitivity (Pérez-López and Merkoçi, 2011) Nanomaterials such as gold nanoparticles (AuNPs), gold nanorods (GNRs), and quantum dots (QDs) are utilized to increase capture efficiency of analytes, signal amplification and improvement of detection limit (DL). The principle behind the DNA detection is based on the simultaneous biorecognition-mediated hybridization of target DNA in a sandwich type manner with two different capture GNRs-DNA probe which leads to aggregation (Ko and Grant, 2006). It successfully detected PCR amplified C. trachomatis pathogen gene (concentration range, 0.25–20 nM). A more comprehensive system that can detect multiple target pathogens simultaneously in a single assay with superior DL is desired
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.