Disaggregation-induced ESIPT: a novel approach towards development of sensors for hyperglycemic condition

Hyperglycaemia is a condition of metabolic disorder in which glycation of human serum albumin (HSA) protein occurs. Upon glycation, the α-helical region of the protein undergoes characteristic changes in its structural features. In this study, we designed a fluorescence probe that can distinguish HSA proteins from glycated HSA (GHSA) proteins. The developed probe contains an oxazolonapthoimidazo[1,2-a]pyridine-based moiety (ONIP1) and was designed using rational computational techniques. The compound exhibits aggregation-induced enhanced emission (AIEE) along with the excited-state intermolecular proton transfer (ESIPT) phenomenon. Density functional theory (DFT) calculations have provided data on ground- and excited-state energy-optimized structures and properties of the proposed enol (N*) and keto (T*) form, which is also in agreement with the solution-state experimental findings and supports the occurrence of the ESIPT phenomenon. Using ONIP1, we were able to distinguish HSA and GHSA proteins via typical modulation of AIEE and ESIPT events.