Silica Nanoparticle-Endothelial Interaction: Uptake and Effect on Platelet Adhesion under Flow Conditions

Abstract

Silica nanoparticles are extensively used in biomedical applications and consumer products. Little is known about the interaction of these NPs with the endothelium and effect on platelet adhesion under flow conditions in circulation. In this study, we investigated the effect of silica nanoparticles on the endothelium and its inflammation, and subsequent adhesion of flowing platelets in vitro. Platelet counts adhered onto the surface of endothelial cells in the presence of nanoparticles increased at both low and high concentrations of nanoparticles. Preincubation of endothelial cells with nanoparticles also increased platelet adhesion. Interestingly, platelet adhesion onto TNF-α-treated endothelial cells decreased in the presence of nanoparticles at different concentrations as compared with the absence of nanoparticles. We monitored the expression of different endothelial proteins, known to initiate platelet adhesion, in the presence and absence of silica nanoparticles. We found that silica nanoparticles caused changes in the endothelium such as overexpression of PECAM that promoted platelet adhesion to the endothelial cell.

Keywords: BAEC; adhesion; blood platelets; endothelium; inflammation; silica nanoparticles.

Figure 1.

(A–D) TEM images of core/shell TRITC-labeled silica nanoparticles with different magnifications. The images were used to measure the mean size and polydispersity of nanoparticles.

Figure 2.

Endothelial cell (EC) monolayer used for the flow experiments [left panel, phase contrast] and image of fluorescent platelets (λ_ex ∼ 485 nm/λ_em ∼ 501 nm) adhered to EC monolayer [right] panel. Scale bar = 20 μm. Image shown is for the SiNP 50 μg/mL concentration after incubation for 12 h.

Figure 3.

Platelet adhesion onto endothelial cells in the presence of different concentrations of SiNPs (**p < 0.01 for platelet adhesion with 10 μg/mL SiNP and *p < 0.10 for platelet adhesion with 250 μg/mL SiNP). (Calculations were added in the Supporting Information, Figures S3 and S4.)

Figure 4.

Platelet adhesion onto inflamed endothelial cells (TNF-α treated) in the presence of SiNPs at different concentrations. (Calculations were added in the Supporting Information, Figure S10.)

Figure 5.

Platelet adhesion onto endothelial cells pretreated with 50 μg/mL SiNPs for 2 h (*p < 0.05 for platelet adhesion with 50 μg/mL SiNP for 12 h). (Calculations were added in the Supporting Information, Figure S10.)

Figure 6.

mRNA expression levels of cell adhesion markers responsible for platelet adhesion and inflammation (*p < 0.05, **p < 0.01, and ***p < 0.001).

Figure 7.

Nitric oxide released by BAECs under different conditions (*p < 0.05 and **p < 0.01).

Scheme 1.

Mechanism of Formation of Core/Shell TRITC-Labeled Silica Nanoparticles