White Light Emission via Twisted Intramolecular Charge Transfer for Monitoring Palmitic Acid-Induced Apoptosis in...

Condition-dependent merging of blue, green, and red light emission to produce white light during cellular imaging from twisted intramolecular charge transfer (TICT)-based molecule has been targeted in this study. Instead of exploiting the typical white light emissive organic molecule (WLE-OM) as a WLE biomarker, our experimental and computational studies focused on donor-π-acceptor (D-π-A)-type iminocoumarin NET-N as the TICT fluorescent probe to monitor cancer cell apoptosis via bioimaging. Steady-state fluorescence studies of NET-N showed blue, yellow, and orange-red emissions in hexane, toluene, and THF, respectively. Synthetic lipids at 7.4 pH buffer showed turn-on orange-red emission of the probe. This study was extended to confirm NET-N as the WLE biomarker for monitoring palmitic acid (PA)-induced cell apoptotic process in lung cancer NCIH460 cells. In contrast, healthy cells did not show merging of three emissive colors from the probe to produce white light emission. After the probe treatment, polarities of the cellular components were responsible for blue/green and green/red emissions from nonpolar and polar environments, respectively. PA treatment increased hydrophobic fatty acids and mitochondrial dysfunction through downregulation of the mitochondrial CPT1a gene, which was responsible for cell apoptosis. Selective white light emission was observed during cell apoptosis via destabilization of fatty acid-mediated lipid droplets in the cytoplasm. In the presence of NET-N, the control experiments with either mitochondrial stress or only fatty acid enhancement did not show white light emission.