A Label‐Free Multitechnique Approach to Characterize the Interaction of Bioactive Compounds with Biomimetic Interfaces

Extensive research has been conducted on biomimetic interfaces mimicking the complex and diverse microenvironment of cell membranes to gain insights into bioactive compound interactions and membrane biophysics modulation. The present study proposes an innovative approach that combines five prospective label-free methodologies (derivative spectroscopy, synchrotron small- and wide-angle X-Ray scattering, attenuated total reflection-Fourier-transform infrared spectroscopy, quartz-crystal microbalance with dissipation, and surface plasmon resonance) to showcase their synergistic capabilities and complementarity in investigating drug-membrane interactions. This multitechnique approach combines the real-time monitoring of the adsorption process under continuous flow conditions with the steady-state perspective of this process. As a proof of concept, the interaction of three bioactive compounds (caffeine, testosterone, and diclofenac) with two biomimetic membrane interfaces (multistacked lipid bilayers and supported lipid bilayers) mimicking the more ordered lipid transient phases, with and without cholesterol (<i>l</i> _o and <i>s</i> _o), that are responsible for a variety of membrane-associated biological activities, is investigated. The biophysical effects of the bioactives are discussed using complementary data from real-time and steady-state experiments, including membrane adsorption and distribution, predicted location, and induced changes in order and fluidity, encompassing bilayer thickness, hydration, and area per lipid molecule.