Coating Graphene Oxide with Lipid Bilayers Greatly Decreases Its Hemolytic Properties

Toxicity evaluation for the proper use of graphene oxide (GO) in biomedical applications involving intravenous injections is crucial, but the GO circulation time and blood interactions are largely unknown. It is thought that GO may cause physical disruption (hemolysis) of red blood cells. The aim of this work is to characterize the interaction of GO with model and cell membranes and use this knowledge to improve GO hemocompatibility. We have found that GO interacts with both neutral and negatively charged lipid membranes; binding is decreased beyond a certain concentration of negatively charged lipids and favored in high-salt buffers. After this binding occurs, some of the vesicles remain intact, while others are disrupted and spread over the GO surface. Neutral membrane vesicles tend to break down and extend over the GO, while vesicles with negatively charged membranes are mainly bound to the GO without disruption. GO also interacts with red blood cells and causes hemolysis; hemolysis is decreased when GO is previously coated with lipid membranes, particularly with pure phosphatidylcholine vesicles

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

Homoleptic organocobalt­(III) compounds with formula [NBu₄]­[Co^III(C₆X₅)₄] [X = F (<b>3</b>), Cl (<b>4</b>)] were obtained in reasonable yields by chemical oxidation of the corresponding divalent species [NBu₄]₂­[Co^II(C₆X₅)₄] [X = F (<b>1</b>), Cl (<b>2</b>)]. The [Co^III(C₆X₅)₄]⁻/[Co^II(C₆X₅)₄]^2– couples are electrochemically related by quasi-reversible, one-electron exchange processes at moderate potential: <i>E</i> _1/2 = −0.29 (X = F) and −0.36 V (X = Cl) versus saturated calomel electrode. The [Co^III(C₆X₅)₄]⁻ anions in salts <b>3</b> and <b>4</b> show an unusual square-planar geometry as established by single-crystal X-ray diffraction methods. According to their stereochemistry, these Co^III derivatives (d⁶) are paramagnetic non-Kramers systems with a large zero-field splitting contribution and no observable electron paramagnetic resonance (EPR) spectrum. The thermal dependence of their magnetic susceptibilities can be explained in terms of a spin-Hamiltonian formalism with <i>S</i> = 1 ground state (intermediate spin) and substantial spin–orbit contribution. The magnetic properties of the square-planar d⁷ parent species [NBu₄]₂­[Co^II(C₆X₅)₄] were also thoroughly studied both at microscopic (EPR) and macroscopic levels (alternating current and direct current magnetization measurements). They behave as <i>S</i> = 1/2 (low spin) systems with mainly (d_<i>z</i>²)¹ electron configuration and a certain degree of s-orbital admixture that has been quantified. The electronic structures of all four open-shell [Co­(C₆X₅)₄]^<i>q</i>− compounds (<i>q</i> = 1, 2) accounting for their respective magnetic properties are based on a common orbital energy-level diagram