Characterization of aptamer cy-apt 20 in vivo. The efficacy of aptamer cy-apt 20 in detecting of gastric cancer in vivo was further determined by IVIS Spectrum Imaging System in dose and time changing manner. The fluorescence signals of tumors relative to background were measured using Image J software and results were presented as fold changes vs. Background ± standard error. (A-B) increased fluorescence signals were detected by increasing the concentration of cy5-labeled cy-apt 20 (from 0.25 nM to 1.5 nM) and peaked at 1.25 nM (arrow notified). (C-D) increased fluorescence signals were also detected by increasing imaging interval (from 10 min to 240 min) at the concentration of 1 nM of cy5-labeled cy-apt 20 and peaked at 120 min (arrow notified).