An environmental route of exposure affects the formation of nanoparticle coronas in blood plasma.

UNLABELLED: Nanoparticles (NPs) in contact with biological fluids become covered by a tightly bound layer of proteins, the "protein corona", and it is largely accepted that this corona gives a new identity to NPs in biological milieu. We here consider the exposing scenario of NPs through an environmental route exemplified by the use of hydrophobins, highly adhesive proteins that are secreted into the environment in large quantities by fungi. HFBII of Trichoderma reesei has been used as a model protein and we have shown strong binding to polystyrene NPs of different sizes and surface groups. Hydrophobin coated NPs are shown to strongly increase the stability and the dispersion when exposed to human plasma compared to pristine ones particles. It is also shown that the presence of hydrophobin on the NPs results in an attenuated protein corona formation, in a different corona composition, and we also show that hydrophobin remained strongly associated to the NPs in competition with plasma proteins. As a conclusion we therefore suggest that the route of exposure of nanoparticles strongly affects their surface properties and their possible physiological behavior. SIGNIFICANCE: This work shows how a self-assembling protein, class II hydrophobin HFBII, with interesting biocompatible coating properties, strongly adsorbs on polystyrene NPs. HFBII is also shown to reduce aggregation of the NPs in human plasma which can increase their bioavailability with potential use in biomedical applications. The results here are also of significance for understanding possible interactions of NPs with living organisms. Hydrophobins are secreted in large quantities into the environment by fungi and this work shows how the biological environment of NPs determines the surface and colloidal properties of the particles by forming a protein corona, and that the history of the particle environment, here simulated with hydrophobin exposure, affects both plasma protein corona formation and dispersion behavior. This work thus simulates how alternative exposure routes affect nanoparticle properties, important in understanding the biological fate of NPs.

Metastable oxidation states of tetrathiafulvalenes on the surface of liposomes.

Redox-active liposomes are prepared by the incorporation of tetrathiafulvalene-cholesterol conjugate 1 in phospholipid vesicles. The oxidation of tetrathiafulvalene (TTF) on the surface of the liposomes in aqueous solution is monitored by UV-vis spectroscopy. It is shown that metastable (TTF+˙)2π-dimers of the mono-oxidized cation radical are formed due to the high local concentration of TTF groups in the lipid membrane. These dimers can be further stabilized by the addition of cucurbit[8]uril or by reduction of the lateral mobility in the membrane by variation of the lipid composition.