Aptamer-based label-free biosensor for fluorescence detection of urinary adenosine
S.-J. Chen, C.-C. Huang, H.-T. Chang
National Taiwan University, TW
Keywords: aptamer, label-free, biosensor, gold nanoparticles, adenosine
Abstract:We have developed a simple, cost-effective, label-free fluorescence biosensor—comprising an adenosine-binding aptamer, gold nanoparticles (Au NPs), and the DNA-binding dye Oligreen (OG)—for the determination of adenosine. The sensitivity of this sensing design was highly dependent on the fluorescence of the aptamer–OG complexes, the quenching efficiency of the Au NPs, and the density of the aptamer–OG complexes on each Au NP, which is strongly related to the concentration of adenosine required to induce the conformational change of the aptamer from coiled to a tertiary structure. For the mixtures of adenosine (0-1.0 μM), 32-nm Au NPs (0.1 nM), aptamer (15 nM), and OG (0.05X) in 5.0 mM phosphate (pH 7.4), a linear correlation (R2 = 0.99) existed between the (IF0 – IF)/IF0 ratios and the concentration of adenosine. The limit of detection for adenosine at a signal-to-noise ratio of 3 was 70 nM. The practicality of this sensitive approach was demonstrated through the determination of the concentration of adenosine in urine samples. Based on the fact that aptamers can undergo conformational change toward various analytes, this fundamental concept opens a new avenue for designing sensors for other important analytes, such as Hg2+, thrombin, and S-adenosylmethionine.