Metal-Enhanced Near Infrared Fluorescence-Based Sensor with Highly Improved Sensitivity for Adenosine Triphosphate

Near infrared (NIR) fluorescent sensor for biologically important analyte is very promising because NIR fluorescence imaging has minimal autofluorescence and high tissue penetration in living system. Nevertheless, its low fluorescence quantum yield leads to low sensitivity of detection. In this study, a functionalized gold nanorods (NIR-AuNRs-3) plasmon enhanced NIR fluorescence-based sensor for adenosine triphosphate (ATP) was developed with highly improved sensitivity. The fluorescence quantum yield with ATP was significantly enhanced, from almost zero to 0.61, resulting in remarkable enhancement of sensitivity. This was attributed to the increase of radiative decay rate of NIR dye by 30-fold, along with almost unchanged nonradiative decay rate. The limit of detection for ATP was 0.6 nM, and it was successfully applied to determine low ATP levels (10.1 ± 2.6 nM) in rat brain. It has been also demonstrated to be useful for monitoring intracellular ATP levels with high sensitivity.