Simultaneous colorimetric detection of a variety of Salmonella spp. in food and environmental samples by optical biosensing using oligonucleotide-gold nanoparticles

Authors: QUINTELA, IRWIN - US Department Of Agriculture (USDA); DE LOS REYES, BENILDO - Texas Tech University; LIN, CHIH-SHENG - National Chaio Tung University; Wu, Vivian

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2019
Publication Date: 5/31/2019
Citation: Quintela, I.A., De Los Reyes, B.G., Lin, C., Wu, V.C. 2019. Simultaneous colorimetric detection of a variety of Salmonella spp. in food and environmental samples by optical biosensing using oligonucleotide-gold nanoparticles. Frontiers in Microbiology. 10:1138. https://doi.org/10.3389/fmicb.2019.01138.
DOI: https://doi.org/10.3389/fmicb.2019.01138

Interpretive Summary: Nanomaterials such as gold noparticles (AuNPs), gold nanorods (GNRs), and quantum dots (QDs) are utilized as excellent optical labels and signal amplifiers that enhance the sensitivity of biosensors. Nanomaterials are also used in developing biosensors to increase its capture efficiency of target molecules. This study utilized oligonucleotide-functionalized nanomaterials (AuNPs) to develop a sensitive detection platform for simultaneous optical biosensing of various Salmonella spp. strains from foods and environmental samples. The sensitive biosensing method can discriminate target from non-target reactions by naked eye. The assay is highly sensitive (<1 log CFU/mL) and 100% specificity, requiring < 1 hr to complete the detection. This detection technology that can simultaneously and directly detect important groups of foodborne pathogens in real food and environmental sample matrices using inexpensive materials can efficiently reduce the risks of foodborne diseases and illnesses.

Technical Abstract: Optical biosensors for foodborne pathogen detection have gained popularity due to its simplicity and sensitivity. Gold nanoparticles (AuNPs) are commonly used as signal amplifiers in nanotechnology-based biosensors but more importantly, it also can be utilized as a stable and efficient biosensing platform. Numerous optical biosensors have been developed but the majority were capable only of detecting pathogens with high detection limits (DL). The aim of this study was to utilize oligonucleotide-functionalized nanomaterials (AuNPs) to develop a sensitive detection platform for simultaneous optical biosensing of various Salmonella spp. strains. An Immuno-magnetic separation (IMS) system was further coupled to concentrate and ensure the detection of viable cells in complex food matrices. The optical biosensor was established by pairs of single stranded thiol-modified oligonucleotides immobilized onto AuNPs, which were used as detection probes to sandwich hybridize 192-bp ttrRSBCA region of Salmonella spp. A highly stable complex resulted from specific hybridization of AuNP-probes and target DNA that retained even after an increase in salt concentration, thus allowing discrimination of target (red color, positive) against non-target (purplish-blue, negative) reaction mixtures by naked eye. A total of 55 natural and inoculated samples were tested, where 40 food samples were Salmonella positive while all five environmental samples tested negative. Transmission electron microscope (TEM) images and absorbance data confirmed AuNP-DNA hybridization. The assay had a superior DL (1 log CFU/mL) and 100% specificity, requiring < 1 hr to complete after sample preparation. This study exploited the unique colorimetric properties of AuNPs for pathogen biosensing at low contamination levels.