Highly Luminescent Thermoresponsive Green Emitting Gold Nanoclusters for Intracellular Nanothermometry and Cellular Imaging: A Dual Function Optical Probe.

In view of many promising applications of gold nanoclusters (AuNCs), nanothermometry is an important field of research in biology and medicine. Here, we demonstrate the temperature dependent photophysical properties of highly luminescent green emitting 6-aza-2-thiothymine/l-arginine-stabilized Au nanosclusters (ATT/Arg Au NCs) by using steady state and time-resolved photoluminescence spectroscopy. Significantly, thermoresponsive properties of these highly photostable and biocompatible Au NCs are reversible, which endow the probe for further bioanalytical applications with great prospects. Additionally, protein-NC interaction mechanism has been elucidated in vitro and in vivo that dictates the complex behavior of the NCs with living organisms. These ultrasmall Au NCs are observed to accumulate in the cellular cytoplasm by translocating through the membrane as evidenced from the confocal laser scanning microscopy (CLSM). In vivo temperature sensing examined with human osteosarcoma cell line (MG-63 cell) by employing fluorescence lifetime imaging microscopy (FLIM) technique reveals the optimistic application of these lifetime-based nanosensors in biomedicine and biotechnology.