Effect of Hydrogenated Cardanol on the Structure of Model Membranes Studied by EPR and NMR

Hydrogenated cardanol (HC) is known to act as an antiobesity, promising antioxidant, and eco-friendly brominating agent. In this respect, it is important to find the way to transport and protect HC into the body; a micellar structure works as the simplest membrane model and may be considered a suitable biocarrier for HC. Therefore, it is useful to analyze the impact of HC in the micellar structure and properties. This study reports a computer aided electron paramagnetic resonance (EPR) and ¹H NMR investigation of structural variations of cetyltrimetylammonium bromide (CTAB) micelles upon insertion of HC at different concentrations and pH variations. Surfactant spin probes inserted in the micelles allowed us to get information on the structure and dynamics of the micelles and the interactions between HC and CTAB. The formation of highly packed HC-CTAB mixed micelles were favored by the occurrence of both hydrophobic (chain–chain) and hydrophilic (between the polar and charged lipid heads) interactions. These interactions were enhanced by neutralization of the acidic HC heads. Different HC localizations into the micelles and micellar structures were identified by changing HC/CTAB relative concentrations and pH. The increase in HC concentration generated mixed micelles characterized by an increased surfactant packing. These results suggested a rod-like shape of the mixed micelles. The increase in pH promoted the insertion of deprotonated HC into less packed micelles, favored by the electrostatic head–head interactions between CTAB and deprotonated-HC surfactants

Effect of Hydrogenated Cardanol on the Structure of Model Membranes Studied by EPR and NMR

Hydrogenated cardanol (HC) is known to act as an antiobesity, promising antioxidant, and eco-friendly brominating agent. In this respect, it is important to find the way to transport and protect HC into the body; a micellar structure works as the simplest membrane model and may be considered a suitable biocarrier for HC. Therefore, it is useful to analyze the impact of HC in the micellar structure and properties. This study reports a computer aided electron paramagnetic resonance (EPR) and ¹H NMR investigation of structural variations of cetyltrimetylammonium bromide (CTAB) micelles upon insertion of HC at different concentrations and pH variations. Surfactant spin probes inserted in the micelles allowed us to get information on the structure and dynamics of the micelles and the interactions between HC and CTAB. The formation of highly packed HC-CTAB mixed micelles were favored by the occurrence of both hydrophobic (chain–chain) and hydrophilic (between the polar and charged lipid heads) interactions. These interactions were enhanced by neutralization of the acidic HC heads. Different HC localizations into the micelles and micellar structures were identified by changing HC/CTAB relative concentrations and pH. The increase in HC concentration generated mixed micelles characterized by an increased surfactant packing. These results suggested a rod-like shape of the mixed micelles. The increase in pH promoted the insertion of deprotonated HC into less packed micelles, favored by the electrostatic head–head interactions between CTAB and deprotonated-HC surfactants

EPR and Rheological Study of Hybrid Interfaces in Gold–Clay–Epoxy Nanocomposites

With the aim to obtain new materials with special properties to be used in various industrial and biomedical applications, ternary “gold–clay–epoxy” nanocomposites and their nanodispersions were prepared using clay decorated with gold nanoparticles (AuNPs), at different gold contents. Nanocomposites structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Rheology and electron paramagnetic resonance (EPR) techniques were used in order to evaluate the molecular dynamics in the nanodispersions, as well as dynamics at interfaces in the nanocomposites. The percolation threshold (i.e., the filler content related to the formation of long-range connectivity of particles in the dispersed media) of the gold nanoparticles was determined to be ϕ_p = 0.6 wt % at a fixed clay content of 3 wt %. The flow activation energy and the relaxation time spectrum illustrated the presence of interfacial interactions in the ternary nanodispersions around and above the percolation threshold of AuNPs; these interfacial interactions suppressed the global molecular dynamics. It was found that below ϕ_p the free epoxy polymer chains ratio dominated over the chains attracted on the gold surfaces; thus, the rheological behavior was not significantly changed by the presence of AuNPs. While, around and above ϕ_p, the amount of the bonded epoxy polymer chains on the gold surface was much higher than that of the free chains; thus, a substantial increase in the flow activation energy and shift in the spectra to higher relaxation times appeared. The EPR signals of the nanocomposites depended on the gold nanoparticle contents and the preparation procedure thus providing a fingerprint of the different nanostructures. The EPR results from spin probes indicated that the main effect of the gold nanoparticles above ϕ_p, was to form a more homogeneous, viscous and polar clay–epoxy mixture at the nanoparticle surface. The knowledge obtained from this study is applicable to understand the role of interfaces in ternary nanocomposites with different combinations of nanofiller

Copper(II) Complexes with 4‑Carbomethoxypyrrolidone Functionalized PAMAM-Dendrimers: An EPR Study

The internal flexibility and interacting ability of PAMAM-dendrimers having 4-carbomethoxypyrrolidone-groups as surface groups (termed Gn-Pyr), which may be useful for biomedical purposes, and ion traps were investigated by analyzing the EPR spectra of their copper­(II) complexes. Increasing amounts (with respect to the Pyr groups) of copper­(II) gave rise to different signals constituting the EPR spectra at room and low temperature corresponding to different coordinations of Cu²⁺ inside and outside the dendrimers. At low Cu²⁺ concentrations, CuN₄ coordination involving the DAB core is preferential for G3- and G5-Pyr, while G4-Pyr shows a CuN₃O coordination. CuN₂O₂ coordination into the external dendrimer layer was also contributing to G3- and G4-Pyr spectra. The structures of the proposed copper–dendrimer complexes were also shown. G4-Pyr displays unusual binding ability toward Cu­(II) ions. Mainly the remarkably low toxicity shown by G4-Pyr and its peculiar binding ability leads to a potential use in biomedical fields