Biomolecular interaction of pretomanid and its pro-liposomal formulation with human serum albumin by multi-spectroscopic, surface plasmon resonance and molecular docking approaches

Pretomanid (PTM) is a new promising candidate for multi- and extensively drug resistant tuberculosis. Based on limited information, PTM lacks an understanding of the drug's impact on protein binding, which may be related to its adverse effects and rational use in clinical practice. Furthermore, the challenges posed by drug properties, especially high hydrophobicity and poor solubility need to be concerned. The pro-liposomal system was formulated to overcome the drawbacks associated with PTM. In this study, the interaction of PTM and its proliposomal formulations on human serum albumin (HSA), a major and important protein in the body, was investigated using various techniques. The fluorescence study revealed that the process of forming PTM-HSA complexes was spontaneous, involving more than one binding site and primarily through static quenching. The hydrophobic forces played a crucial role in the PTM-HSA interaction. The kinetics of PTM and liposomal PTM were evaluated using surface plasmon resonance measurements, and all samples fitted into a two-state reaction model. Liposomal PTM exhibited a decreasing binding affinity and conformational changes compared to PTM alone. The UV-visible, circular dichroism and three-dimensional fluorescence spectra disclosed some changes in the microenvironment of HSA through hydrophobicity at residual aromatic amino acids. However, the liposomal PTM showed a lower effect on HSA structure than observed with PTM alone. Furthermore, both site marker competitive studies and molecular docking unveiled separate binding locations on HSA following treatment with PTM (Site IIA) and liposomal PTM (Site IB), predominantly influenced by hydrophobic forces. The findings of this study provided knowledge on the mechanism of PTM or liposomal PTM on HSA binding for further studies on the pharmacokinetics, pharmacodynamics, and toxicity of PTM.