A cationic detergent based dye supramolecular assembly as a unique turn-on probe for ATP quantification

Abstract

Adenosine triphosphate (ATP) is an extremely important bio-molecule, which plays a crucial role in various biological processes by releasing the energy stored in it. Thus, abnormal ATP concentration in the body can hamper normal biological activities, which can ultimately lead to serious physiological disorders. Therefore, fast, label-free methods such as fluorescence-based methods for ATP quantification are highly necessary. Herein, we report a supramolecular assembly of a dansylated gemcitabine derivative (GEM-DNS) and cationic detergent cetyltrimethylammonium bromide (CTAB) as a turn-on fluorescence probe for ATP quantification. Similar to free dye solution, the combination of 0.25 mM CTAB with an aqueous dye exhibits very feeble emission, but the dye-surfactant mixture displays dramatic enhancement in fluorescence intensity with an increase in the ionic strength of the solution. This prompted the utilization of the dye-CTAB mixture for the detection of ATP at physiological pH. ATP, owing to its high negative charge density, efficiently induces aggregation to the cationic CTAB molecules. These newly formed aggregates encapsulate the dye into their hydrophobic cavities leading to the formation of a GEM-DNS@CTAB@ATP ternary complex, which eventually results in a significant surge in the fluorescence intensity of the bound dye. This fluorescence enhancement is directly proportional to ATP concentration in the dynamic range of 0 to 4.5 μM, allowing us to quantify ATP with a limit of detection of ∼0.25 μM in a buffer. Furthermore, the turn-on signal for the GEM-DNS@CTAB complex is found to be highly selective towards ATP, enabling its quantification even in diluted human serum samples. Consequently, our system provides a novel and promising platform for ATP quantification owing to its several advantages such as a large Stokes shift, high signal-to-noise ratio, low background, high brightness, and minimum possibility of false signals.