Amine modification of nonporous silica nanoparticles reduces inflammatory response following intratracheal instillation in murine lungs

Abstract

Amorphous silica nanoparticles (NPs) possess unique material properties that make them ideal for many different applications. However, the impact of these materials on human and environmental health needs to be established. We investigated nonporous silica NPs both bare and modified with amine functional groups (3-aminopropyltriethoxysilane (APTES)) in order to evaluate the effect of surface chemistry on biocompatibility. In vitro data showed there to be little to no cytotoxicity in a human lung cancer epithelial cell line (A549) for bare silica NPs and amine-functionalized NPs using doses based on both mass concentration (below 200μg/mL) and exposed total surface area (below 14m(2)/L). To assess lung inflammation, C57BL/6 mice were administered bare or amine-functionalized silica NPs via intra-tracheal instillation. Two doses (0.1 and 0.5mg NPs/mouse) were tested using the in vivo model. At the higher dose used, bare silica NPs elicited a significantly higher inflammatory response, as evidence by increased neutrophils and total protein in bronchoalveolar lavage (BAL) fluid compared to amine-functionalized NPs. From this study, we conclude that functionalization of nonporous silica NPs with APTES molecules reduces murine lung inflammation and improves the overall biocompatibility of the nanomaterial.

Keywords: A549 cells; Amine-functionalized silica; Inflammation; Nanomaterials; Nanotoxicology.

Fig. 1

SEM image of nonporous silica NPs(A) and Min-U-Sil(B).

Fig. 2

Percent relative cell viability of A549 cells treated with bare silica NPs (black) and APTES-functionalized NPs (grey). The first row shows percent relative cell viability from doses prepared using mass concentration of NPs ranging from 10–200 μg/mL at 4(A), 24(B) and 48(C) hours. The second row shows percent relative cell viability from doses prepared using exposed surface area of NPs ranging from 0.69–14 m²/L at 4(D), 24(E) and 48(F) hours. Data are expressed at mean ± standard error. ** p < 0.01

Fig. 3

Percent change in body weight of mice after 24 hours of treatment of 0.1 mg/mouse and 0.5 mg/mouse. Control mice were treated with PBS instead of particles. ** p < 0.01

Fig. 4

Total number of cells in BAL fluid after administration of 0.1 mg silica/mouse (A) or 0.5 mg silica/mouse (B). * p < 0.05, ** p < 0.01, **** p < 0.0001

Fig. 5

Neutrophils and macrophages in BAL fluid after administration of 0.1 mg silica/mouse (A) or 0.5 mg silica/mouse (B). * p < 0.05, *** p < 0.001

Fig. 6

Total protein and LDH activity after administration of 0.1 mg silica/mouse (A) or 0.5 mg silica/mouse (B). * p < 0.05, ** p < 0.01, **** p < 0.0001

Fig. 7

Production of intracellular ROS/RNS after administration of 0.1 mg silica/mouse (A) or 0.5 mg silica/mouse (B). * p < 0.05, *** p < 0.001, **** p < 0.0001