Potential fluorescent probe ethyl 3-(2-(1H-benzo[d]imidazol-2-yl)-5 methoxynaphthalen-1-yl)propanoate for real-time monitoring of human serum albumin dynamics and cancer cell imaging

Abstract

A recently synthesised benzimidazole derivative, ethyl 3-(2-(1H-benzo[d]imidazol-2-yl)naphthalen-1-yl)propanoate (EBINP), demonstrates pronounced environment-sensitive fluorescence, with red-shifted emission in polar solvents. In Tris–HCl buffer, EBINP exhibits enhanced fluorescence along with a blue shift upon interaction with human serum albumin (HSA) and sodium dodecyl sulfate (SDS). Fluorometric titration combined with Benesi–Hildebrand analysis reveals a 1 : 1 binding stoichiometry with HSA, driven by favourable thermodynamic interactions. EBINP is further utilised to investigate protein–surfactant interactions. Förster resonance energy transfer (FRET) from HSA to EBINP confirms close spatial proximity and a high quenching constant. Time-resolved fluorescence measurements reveal notable lifetime variations associated with changes in the local microenvironment, particularly during SDS-induced unfolding. Dynamic light scattering (DLS) and zeta potential analyses are performed to characterise these structural and surface charge variations. These findings establish EBINP as a highly responsive fluorescent probe for monitoring protein conformational dynamics and microenvironmental polarity. Computational modelling employing docking and classical molecular dynamics simulations strongly corroborates the experimental results, demonstrating significantly strong binding of EBINP with HSA through predominant hydrophobic and van der Waals interactions. EBINP + HSA nanoparticles exhibit enhanced fluorescence intensity and improved uptake by cancer cells compared to EBINP alone, showing moderate anticancer activity while maintaining low toxicity, thereby illuminating their potential for targeted cancer imaging and therapy.