Spécialité: Sciences du Médicament

A label-free, homogeneous aptamer-based sensor strategy was designed for the facile colorimetric detec-tion of small target molecules. The format relied on the target-induced protection of DNA aptamer fromthe enzymatic digestion and its transduction into a detectable signal through the length-dependentadsorption of single-stranded DNA onto unmodified gold nanoparticles (AuNPs). The proof-of-principleof the approach was established by employing the anti-tyrosinamide aptamer as a model functionalnucleic acid. In the absence of target, the aptamer was cleaved by the phosphodiesterase I enzymaticprobe, leading to the release of mononucleotides and short DNA fragments. These governed effectiveelectrostatic stabilization of AuNPs so that the nanoparticles remained dispersed and red-colored uponsalt addition. Upon tyrosinamide binding, the enzymatic cleavage was impeded, resulting in the protec-tion of the aptamer structure. As this long DNA molecule was unable to electrostatically stabilize AuNPs,the resulting colloidal solution turned blue after salt addition due to the formation of nanoparticle aggre-gates. The quantitative determination of the target can be achieved by monitoring the ratio of absorbanceat 650 and 520 nm of the gold colloidal solution. A limit of detection of ∼5 mM and a linear range up to100 mM were obtained. The sensing platform was further applied, through the same experimental proto-col, to the adenosine detection by using its DNA aptamer as recognition tool. This strategy could extendthe potentialities, in terms of both simplicity and general applicability, of the aptamer-based sensingapproaches.© 2011 Elsevier B.V. All rights reserved.