Design and synthesis of ionic tetraphenylbuta-1,3-diene derivatives: photophysical properties and their suitability in biological environments

This work presents the rational design and successful synthesis of three ionic tetraphenylbuta-1,3-diene (TPB) derivatives (TPB-Py-butyl, TPB-Py-SO₃, and TPB-Py-NMe₃) with short alkyl chains, containing different terminal groups. While the aromatic core remains unchanged, the overall charge of the moiety is modulated by altering the terminal ionic group attached to the alkyl chains. These derivatives exhibit excellent water solubility, allowing us to investigate the detailed photophysical studies in aqueous environments. Temperature-dependent photoluminescence (PL) studies indicate that these moieties display highly reversible emission in water with good linearity and fatigue resistance. Additionally, their ionic natures are leveraged to evaluate their interactions with and stabilization of DNA G-quadruplex structures, including c-myc, c-kit, bcl2, KRAS, and VGEF. Among the three ionic TPBs, the tetra-cationic TPB-Py-NMe₃ derivative has revealed the highest stabilization efficiency, particularly towards c-myc. Cytotoxicity assessments using the MTT assay have confirmed that these TPBs exhibit low cytotoxicity while displaying anticancer activity. The combination of their reversible optical properties, DNA binding capabilities, and biocompatibility highlights their potential applications in biosensing, bioimaging, and cancer therapeutics.