Crystallographic and theoretical insights into a fluorogenic turn-on probe for selective Fe3+ detection with biomolecular binding and in vitro anticancer studies.

Ferric ions (Fe3+) play essential roles in oxygen transport and enzymatic processes, while their dysregulation is associated with disorders such as anaemia and cancer. In this study, we report the design of a fluorescent probe, HMC, for the selective and reversible detection of Fe3+. The probe displays weak intrinsic emission but exhibits a "turn-on" fluorescence response, shifting from colourless to green upon Fe3+ binding, with a detection limit of 1.86 μM. The Fe3+-induced emission is reversible through Na2EDTA treatment. Furthermore, HMC exhibited sensitivity in biological studies through a specific interaction with calf-thymus DNA (ct-DNA), which resulted in a hypsochromic shift and threefold fluorescence enhancement (LOD ∼4.92 μM), while binding to bovine serum albumin (BSA) produced a strong emission increase with a new peak at 481 nm (LOD ∼4.8 × 10-3 μM). The experimental studies were supported by molecular docking, revealing strong binding affinities of HMC to ct-DNA (-10.3 kcal mol-1) and BSA (-12.4 kcal mol-1). HMC exhibited pronounced fluorescence enhancement upon interaction with Fe3+, enabling efficient detection in biological samples, and showed moderate dose-dependent cytotoxicity against MCF-7 breast cancer cells as confirmed by MTT assays.