Aptamer biosensor for Salmonella typhimurium detection based on luminescence energy transfer from Mn2 +-doped NaYF4:Yb, Tm upconverting nanoparticles to gold nanorods
A highly sensitive luminescent bioassay for the detection of Salmonella typhimurium was fabricated using Mn 2 + -doped NaYF 4 :Yb,Tm upconversion nanoparticles (UCNPs) as the donor and gold nanorods (Au NRs) as the acceptor and utilizing an energy transfer (LET) system. Mn 2 + -doped NaYF 4 :Yb,Tm UCNPs with a strong emission peak at 807 nm were obtained by changing the doped ion ratio. Carboxyl-terminated Mn 2 + -doped NaYF 4 :Yb,Tm UCNPs were coupled with S. typhimurium aptamers, which were employed to capture and concentrate S. typhimurium . The electrostatic interactions shorten the distance between the negatively charged donor and the positively charged acceptor, which results in luminescence quenching . The added S. typhimurium leads to the restoration of luminescence due to the formation of UCNPs-aptamers- S. typhimurium , which repels the UCNPs-aptamers from the Au NRs. The LET system does not occur because of the nonexistence of the luminescence emission band of Mn 2 + -doped NaYF 4 :Yb,Tm UCNPs, which had large spectral overlap with the absorption band of Au NRs. Under optimal conditions, the linear range of detecting S. typhimurium was 12 to 5 × 10 5 cfu/mL (R = 0.99). The limit of detection for S. typhimurium was as low as 11 cfu/mL in an aqueous buffer. The measurement of S. typhimurium in milk samples was satisfied in accordance with the plate-counting method, suggesting that the proposed method was of practical value in the application of food security.
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