A terbium-based metal-organic framework@gold nanoparticle system as a fluorometric probe for aptamer based determination of adenosine triphosphate

This study reports on a method for fluorometric aptasensing of adenosine triphosphate (ATP). It is based on the interaction of dispersed (red) and agglomerated (blue) gold nanoparticles (AuNPs) with a water-dispered terbium(III) based metal-organic framework (Tb-MOF). The dispersed AuNPs quench the emissions of the Tb-MOF, while the aggregated AuNPs have little effect. Under the condition of high salt concentration, the free aptamer against ATP does not stabilize the AuNPs against aggregation. This causes a color change from red to blue and weak quenching of the fluorescence of the Tb-MOF (with peaks at 489 nm and 544 nm after excitation at 290 nm). On addition of ATP, it will be bound by its aptamer to form a complex that is adsorbed on the AuNPs. This protects the AuNPs from salt-induced aggregation and the color (with a peak at 525 nm) remains red. The two fluorescence bands of the Tb-MOF are therefore suppressed by fluorescence resonance energy transfer (FRET) between Tb-MOF and the dispersed AuNPs. Fluorescence drops linearly in the 50 nM to 10 mu M ATP concentration range, and the detection limit is 23 nM. ATP analogs such as guanosine triphosphate, uridine triphosphate, cytidine triphosphate, adenosine monophosphate and cyclic adenosine monophosphate have no obvious interference. The method was successfully applied to the determination of ATP in (spiked) human plasma samples and gave satisfactory recoveries.