We present here a pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This pH-responsive activatable aptamer probe is composed of two single-stranded DNA. One was used for target recognition, containing a central, target specific aptamer sequence at the 3＇-end and an extension sequence at the 5＇-end with 5-carboxytetramethylrhodamine （TAMRA） label （denoted as strand A）. The other （strand ｜）, being competent to work on the formation of i-motif structure, contained four stretches of the cytosine （C） rich domain and was labeled with a Black Hole Quencher 2 （BHQ2） at the 3＇-end. At neutral or slightly alkaline pH, strand ｜ was hybridized to the extension sequence of strand A to form a double-stranded DNA probe, termed i-motif-based activatable aptamer probe （I-AAP）. Because of proximity- induced energy transfer, the I-AAP was in a ＂signal off＇ state. The slightly acidic pH enforced the strand I to form an intramo- lecular i-motif and then initiated the dehybridization of I-AAP, leading to fluorescence readout in the target recognition. As a demonstration, AS1411 aptamer was used for MCF-7 cells imaging. It was displayed that the I-AAP could be carried out for target cancer cells imaging after being activated in slightly acidic environment. The applicability of I-AAP for tumor tissues imaging has been also investigated by using the isolated MCF-7 tumor tissues. These results implied the I-AAP strategy is promising as a novel approach for cancer imaging.
The Ru（bpy）3^2＋ doped graphene oxide-silica composite film（Ru/GO-SiCF） was synthesized by one pot hydrolysis and condensation of tetraethylorthosilicate（TEOS） in the water-alcohol solution of graphene oxide and Ru（bpy）3^2＋ at room temperature.The prepared Ru/GO-SiCF modified glassy carbon electrode（GCE） showed excellent electrochemiluminescence（ECL） behavior for the determination of tripropylamine（TPA） with high sensitivity and good stability.We expected this simple and novel material will find further application in construction of other targets sensors.
Gen-Ping YanXiao-Xiao HeKe-Min WangYong-Hong WangJin-Quan LiuLi-Xin JianYin-Fei Mao
