In a physiological environment, nanoparticles selectively absorb proteins to form 'nanoparticle-protein coronas', a process governed by molecular interactions between chemical groups on the nanoparticle surfaces and the amino-acid residues of the proteins. Here, we propose a biological surface adsorption index to characterize these interactions by quantifying the competitive adsorption of a set of small molecule probes onto the nanoparticles. The adsorption properties of nanomaterials are assumed to be governed by Coulomb forces, London dispersion, hydrogen-bond acidity and basicity, polarizability and lone-pair electrons. Adsorption coefficients of the probe compounds were measured and used to create a set of nanodescriptors representing the contributions and relative strengths of each molecular interaction. The method successfully predicted the adsorption of various small molecules onto carbon nanotubes, and the nanodescriptors were also measured for 12 other nanomaterials. The biological surface adsorption index nanodescriptors can be used to develop pharmacokinetic and safety assessment models for nanomaterials.
Carbon fullerenes possess unique properties and their interactions with biomolecules have widespread applications. Functionalization of fullerenes with hydroxyl groups (fullerenols) can increase the solubility and potential for cellular interaction, but the health and safety effects of varying degrees of fullerene hydroxylation in biological systems is poorly understood. Existing reports regarding the toxicity and inflammatory potential of fullerenols give conflicting conclusions. To further elucidate the potential for toxicity of fullerenols, human epidermal keratinocytes (HEK) were exposed to fullerenols (low (C60(OH)20), medium (C60(OH)24), and high (C60(OH)32)) at concentrations ranging from 0.000544–42.5μg/ml for 24 and 48h. A statistically significant (p < 0.05) decrease in viability with alamar Blue (aB) was noted only with C60(OH)32 at 42.5μg/ml after 24h. Nanoparticle (NP) controls showed minimal NP/assay interference of the three fullerenols with the aB viability assay. Normalized IL-8 concentration for C60(OH)20 was not significantly different from control, while C60(OH)24 and C60(OH)32 showed a significant decrease at 24 and 48h. These results suggest that different hydroxylation of fullerenes caused no cytotoxicity or inflammation up to 8.55μg/ml. These findings suggest that extrapolation across similar NP will be dependent upon surface chemistry and concentration which may affect the degree of agglomeration and thus biological effects.
C18-bonded silica-coated multifibers were prepared and studied as a stationary phase for solid-phase microextraction (SPME). The porous multifiber SPME provided larger absorption capacity and higher absorption rate compared to a polymer-coated single fiber. Its absorption rate was 10 times higher than that of a commercial 100-microm poly(dimethylsiloxane) (PDMS)-coated fiber. Its high extraction efficiency enabled the positive identification of unknown compounds at sub-part-per-billion level in full-scan mode with a benchtop quadruple GC/MS. The desorption temperature indicated that the analyte interactions with the C18-bonded silica were stronger than those with the PDMS polymer. The dependence of the equilibration time on the molecular weight was not observed for the porous multifiber SPME. The boundary layer between the fiber coating and the sample matrix could be the absorption control step in SPME under mild agitation. The special experimental conditions in the porous multifiber SPME, such as air interference and polar organic solvent wetting, were investigated.
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