Development of a natural product-based selective fluorescent sensor for Cu2+ and DNA/protein: insights from docking, DFT, cellular imaging and anticancer activity.

The natural product seselin (SS), was synthesized and characterized spectroscopically for the selective detection of Cu²⁺ and biomolecules such as ct-DNA and BSA. The probe exhibits strong bluish emission in a MeOH-H₂O (7 : 3, v/v) HEPES buffer solution (pH 7.4) at 453 nm. Upon exposure to Cu²⁺, the SS solution shows a selective fluorescence 'turn-off' with a binding constant of 2.13 × 10⁵ M^-1 and a detection limit of 3.48 × 10^-8 M. The HOMO-LUMO energy gap of the probe SS decreases from ΔE = 7.97 eV to ΔE = 7.77 eV upon binding with Cu²⁺, indicating enhanced stability due to ligand-metal complex formation. Significantly, the ligand SS exhibits fluorescence enhancement in the presence of ct-DNA and BSA, resulting in a visible fluorescence change from colorless to blue, with binding constants of 4.8 × 10⁴ M^-1 and 4.7 × 10⁴ M^-1, respectively. The binding interactions of SS with biomacromolecules have been explored through molecular docking studies, revealing that the probe can serve as a promising anti-cancer and anti-viral agent. Furthermore, the probe SS demonstrates potent anticancer activity in treatments involving MCF-7 and HLC cells. Additionally, the probe SS is capable of detecting intracellular Cu²⁺ in live MCF-7 cell lines.