Hydrophilic iron oxide nanoparticles probe the organization of biomimetic layers: Electrochemical and spectroscopic evidence

Abstract Biomimetic films of mixed lipids were challenged with 15 nm hydrophilic, superparamagnetic, iron oxide-based magnetic nanoparticles (SPIONs). These nanoparticles were stabilized with citrate and were allowed to interact with lipidic Langmuir films spread on an aqueous subphase or with Langmuir-Blodgett (LB) monolayers and Langmuir-Blodgett/Langmuir Schaeffer (LB/LS) bilayers transferred onto solid supports. The goal of this work is to evaluate the nature of SPIONs-cellular membrane interactions, and to attempt to separate the physicochemical aspects of such interactions from the biological ones. The ultimate utility of SPIONs lies in their potential for medical applications, such as targeted drug delivery, magnetic resonance imaging or theranostics in general. Systematic experimental studies were carried out with complementary techniques, such as LB and LB/LS film deposition, Brewster angle microscopy (BAM) imaging of the films, electrochemical impedance spectroscopy, surface enhanced resonance Raman spectroscopy SE(R)RS and fluorescence lifetime and anisotropy decay imaging (FLIM and FADI) techniques. The data presented here indicate that SPIONs have a measurable effect on the phase behavior of mixed monolayers, altering the organization of monolayer and bilayer films, and inducing changes in the formation of domains.