Endothelial cell aging detection by means of atomic force spectroscopy.

Endothelial cell aging is related to changes not only in cell phenotype, such as luminal changes, intimal and medial thickening, and increased vascular stiffness, but encompasses different cell responses to various substances including drugs or nanomaterials. In the present work, time- and dose-dependent elasticity changes evoked by silver nanoparticles in endothelial cells in early (below 15) passages were analyzed. Silver nanoparticle concentrations of 3, 3.6, and 16 µg/mL were selected for elasticity measurements for long incubation (24 hours) and of 1 and 3 µg/mL for monitoring dynamic elasticity changes of 1-, 3-, and 6-hour incubations. Surprisingly, a significant reduction in the cells elasticity modulus at lower number of passages exposed to silver nanoparticles used at 3 µg/mL for 24 hours was demonstrated. These results are in contrast to those obtained for endothelial cells in late (33-43) passages that may result from cellular aging in response to nanosilver. Furthermore, for short incubation times (1 and 3 hours), SNP-induced significant increase in the cell elasticity modulus was detected. In current work, we also attempted to answer the question whether the changes in cell elasticity were induced by the silver nanoparticles stabilized with polyvinyl pyrrolidone or by stabilizer itself. Elasticity measurements were supplemented by observations made with transmission electron microscopy and scanning electron microscopy, which confirmed the presence of silver nanoparticles inside the cells and on the cell membrane. Additionally, activation of reactive oxygen species was detected for cells exposed to SNPs for 1 and 3 hours, which was accompanied by increased cell elasticity modulus suggesting a possible mechanism of observed phenomenon.

Effect of the alkyl chain length of secondary amines on the phase transfer of gold nanoparticles from water to toluene.

In the present paper we describe a phase transfer of aqueous synthesized gold nanoparticles (AuNPs) from water to toluene using secondary amines: dioctylamine, didodecylamine, and dioctadecylamine. The effect of the hydrocarbon chain length and amount of amines on the transfer efficiency were investigated in the case of nanoparticles (NPs) with three different sizes: 5, 9, and 13 nm. Aqueous colloids were precisely characterized before the transfer process using UV-vis spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Nanoparticles were next transferred to toluene and characterized using UV-vis and DLS techniques. It was found that dioctadecylamine provides the most effective transfer of nanoparticles. No time-dependent changes in the NP size were observed after 12 days, showing that the dioctadecylamine-stabilized nanoparticles dispersed in toluene were stable. This indicates that long hydrocarbon chains of dioctadecylamine exhibit sufficiently hydrophobic properties of nanoparticles and consequently their good dispersibility in nonpolar solvent.