Sunflower-like Fluorescent Self-Assembled Morphologies Formed by Pyridothiazole Based Aggregation Induced Emission (AIE) Dye and Its Cell Imaging Applications

We report for the very first-time self-assembly of 4-(5-methoxythiazolo[4,5-b]pyridin-2-yl)-N,N-dimethylaniline (TPA) to fluorescent sunflower-like architectures. Interestingly, TPA exhibits blue fluorescence in visible light at 385 nm and the fluorescence is not affected by photo-induced quenching rather the fluorescence keeps on increasing with time under broad day light. The morphologies of self-assembled structures of TPA were studied at various concentrations in dimethyl sulphoxide (DMSO) and Tetrahydrofuran (THF). The microscopic studies through SEM and fluorescence microscopy reveal the formation of sunflower-like fluorescent self-assemblies. Further, our study revealed that the sunflower shaped assemblies formed by TPA exhibitfluorescence under blue, green, and red channels that can be evinced by the fluorescence spectroscopy and microscopy. Hence TPA exhibits panchromatic emission properties and it reveals tunable emission properties under different excitation wavelengths. Further, AIE properties of TPA were evinced by recording fluorescence in THF under varying concentrations of water and doing solvent chromic studies.Finally,the utility of TPA as a cell imaging agent was studied in human breast cancer cell lines (MDA-MB-231) which suggested TPA can penetrate the cell membrane and can be effectively used as a cell labeling dye.