Effect of Silica Surface Properties on the Formation of Multilayer or Submonolayer Protein Hard Corona: Albumin Adsorption on Pyrolytic and Colloidal SiO₂ Nanoparticles

Abstract

The adsorption of bovine serum albumin (BSA) on two types of silica nanoparticles (NPs), one pyrolytic (P−SiO 2 ; namely AOX50 by Evonik) and the other colloidal (lab-made by using inverse micelles microemulsion, M−SiO 2 ), is studied. Both materials are characterized in terms of size of primary particles (by transmission electron microscopy), amounts (by thermogravimetry) and distribution of silanols (IR spectroscopy in controlled atmosphere, augmented by H/D isotopic exchange and reaction with VOCl 3 , to distinguish silanols actually located at the surface of nanoparticles), water contact angle, ζ−potential and dispersion state in water, PBS buffer and BSA solutions in PBS (by dynamic light scattering, DLS). Proteins are found to act as dispersing agent toward the large aggregates formed by both types of NPs in PBS buffer, although monodispersion was not attained in the conditions investigated. The problem of the determination of the silica surface actually available in NPs agglomerates for protein adsorption is addressed, and a model based on the external area of the agglomerates determined by DLS is proposed, supported by the trend of ζ−potential in dependence on the amount of adsorbed BSA and by the UV circular dichroism spectra of adsorbed proteins. The spectra reveal the occurrence of protein-protein interactions for BSA on P−SiO 2 , where multilayers of irreversibly adsorbed BSA molecules (i.e. a so called protein hard corona) are proposed to be formed. Conversely, the model indicates the formation of a sub-monolayer protein hard corona on M−SiO 2 . The difference in protein coverage appears to be related to differences in the distribution of surface silanols, more than to differences in ζ−potential.

Adsorption of bovine serum albumin on silicon dioxide nanoparticles: Impact of pH on nanoparticle–protein interactions

“…40 Catalano et al reported an alpha helix content of approximately 36% for BSA adsorbed onto pyrolytic SiO 2 nanoparticles. 58 All previously reported results have a much lower content than what was measured in these studies, which can be due to the different nanoparticles used. Neither Lehman et al nor Catalano et al used water as the dispersant, 40,58 and Catalano et al reported that the media influence protein-nanoparticle interactions.…”

“…58 All previously reported results have a much lower content than what was measured in these studies, which can be due to the different nanoparticles used. Neither Lehman et al nor Catalano et al used water as the dispersant, 40,58 and Catalano et al reported that the media influence protein-nanoparticle interactions. 58 The porosity of the nanoparticles may influence the adsorption of BSA to nanoparticle surfaces.…”

“…Neither Lehman et al nor Catalano et al used water as the dispersant, 40,58 and Catalano et al reported that the media influence protein-nanoparticle interactions. 58 The porosity of the nanoparticles may influence the adsorption of BSA to nanoparticle surfaces. 59 A comparison study between TiO 2 and SiO 2 nanoparticles found that the surface hydroxyl groups available for nanoparticles differ, 56 which change depending on the generation method for SiO 2 nanoparticles.…”

Segregation of Dispersed Silica Nanoparticles in Microfluidic Water‐in‐Oil Droplets: A Kinetic Study

“…Furthermore, negligible electrostatic attraction between BSA and DOTAP has previously been observed at measured pH 6.5 . We, therefore, conclude that the physisorbed BSA molecules on the particle's surface effectively screen the negative charge of SiNP‐1 , thereby resulting in a weak interaction between SiNP‐3 (BSA) and the DOTAP shell.…”

Indoor illumination: A possible pitfall in toxicological assessment of photo-active nanomaterials

“…In the case of nanomaterials (NMs) standardization is a particularly relevant issue. Numerous specific and non-specific factors have been shown to influence the results of toxicological testing [3], such as: i) the degree of dispersion of the NM, that varies depending upon the media used [4,5,6], ii) the real dose, that, oppositely to molecular substances may not correspond to the nominal one [7,8], iii) the presence of contaminants in the materials like bacterial lipopolysaccharides (LPS) [9] or metal ions [10] iv) the occurrence of artefacts due to adsorption of reagents or intrinsic absorbance/fluorescence of the material [3,11,12]. Much less explored is the effect of illumination during the preparation of samples and NM exposure in toxicological testing.…”