A gold nanoparticles-modified aptamer beacon for urinary adenosine detection based on structure-switching/fluorescence-“turning on” mechanism

A novel small molecule probe, aptamer beacon (AB), was introduced for adenosine (Ade) recognition and quantitative analysis. The Ade aptamer was engineered into an aptamer beacon by adding a gold nanoparticle-modified nucleotide sequence which is complementary to aptamer sequence (FDNA) at the 3′-end of FDNA. The fluorescence signal “turning on” was observed when AB was bound to Ade, which is attributed to a significant conformational change in AB from a FDNA/QDNA duplex to a FDNA-Ade complex. The Ade measurement was carried out in 20 mmol L−1 Tris-HCl buffer solution of pH 7.4, ΔF signal linearly correlated with the concentration of Ade over the range of 2.0 × 10−8 to 1.8 × 10−6 mol L−1. The limit of detection (LOD) for Ade is 6.0 × 10−9 mol L−1 with relative standard deviations (R.S.D) of 3.64-5.36%, and the recoveries were 98.6%, 100%, 102% (n = 6), respectively. The present method has been successfully applied to determine Ade in human urine samples, and the obtained results were in good agreement with those obtained by the HPLC method. Our investigation shows that the unique properties of the AB could provide a promising potential for small molecules detection, and be benefit to extend the application of aptamer beacon technique.