A fluorescent aptasensing strategy for adenosine triphosphate detection using tris(bipyridine)ruthenium(II) complex containing six cyclodextrin units

A sensitive label-free fluorescent aptasensing strategy for the detection of adenosine triphosphate (ATP) has been developed with a metallocyclodextrin, tris(bipyridine)ruthenium(II) complex containing six cyclodextrin units (6CD-Ru), which exhibited much stronger emission signal compared to the parent compound Ru(bpy)₃Cl₂. Furthermore, the emission spectrum showed that the ATP-aptamer (ssDNA) could increase the fluorescence intensity of 6CD-Ru dramatically, attributed to the interaction between aptamer and cyclodextrin, which could provide protection to the ruthenium core from the quenching of emission by oxygen in the solution. With the addition of ATP, the interaction between aptamer and cyclodextrins on 6CD-Ru was diminished, since the ATP/aptamer complex had the priority to be formed, leading to the corresponding reduction of fluorescence intensity, which could be utilized to detect ATP quantitatively. A linear relationship was displayed between the fluorescence and the logarithm of ATP concentrations in the range from 1 nmol/L to 1 μmol/L with the detection limit of 0.5 nmol/L (S/N = 3). The proposed fluorescent aptasensing strategy exhibited high sensitivity and specificity, without any labeling or amplification procedures, and it could also be applied for the detection of many other aptamer-specific targets.