Binding Effect of Common Ions to Human Serum Albumin in the Presence of Norfloxacin: Investigation with Spectroscopic and Zeta Potential Approaches

In this work, the toxic influence of metallic ions (Al3+, Cu2+, Mg2+, Pb2+) on human serum albumin (HSA) in the absence and presence of norfloxacin (NRF) was studied by spectroscopic approaches [fluorescence quenching, synchronous fluorescence, three-dimensional fluorescence, circular dichroism, resonance light scattering (RLS) and zeta potential techniques] under simulated physiological conditions. Fluorescence spectroscopy revealed that these metallic ions and NRF can quench the HSA fluorescence, and this quenching effect became more significant when both ion and drug are present together. The binding constants and binding sites of metal ions with HSA in the absence and presence of NRF were determined, based on the fluorescence quenching results. Ion aggregation gives rise to an enhancement of the RLS intensity for HSA and the critical induced aggregation concentration (C (CIAC)) of the ions, causing HSA aggregation for binary and ternary systems. The zeta potential measurements indicate a combination of electrostatic and hydrophobic interactions between ion, NRF and HSA and the formed micelle-like clusters. These data illustrated that NRF has an effect on the interaction between HSA and metal ions, with relevance for various toxicological and therapeutic processes.