Surface Energy of Silica Xerogels and Fumed Silica by Inverse Gas Chromatography and Inverse Liquid Chromatography

Abstract Inverse gas chromatography (IGC) and inverse liquid chromatography (ILC) have been used to detect the interaction energy between silicas (fumed silicas and silica xerogels) surfaces and probes molecules. The silica surfaces were modified chemically by trimethylsiloxane functions. Either IGC or ILC have detected the adsorption energy change following the surface modification. In IGC technique, the results with several probes show clearly the physico-chemical properties of the silica surfaces. ILC was developed to use bigger probe molecules which are more similar in structure to polymers. In this work, squalene, a non volatile molecule with 30 carbon atoms and several double bonds, was used in ILC to simulate elastomer molecules.

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Characterization of Silica Xerogels Surfaces by Inverse Gas Chromatography (IGC)

Rubber Chemistry and Technology ◽

10.5254/1.3547610 ◽

2000 ◽

Vol 73 (4) ◽

pp. 634-646 ◽

Cited By ~ 9

Author(s):

J. B. Donnet ◽

T. K. Wang ◽

Y. J. Li ◽

H. Balard ◽

G. T. Burns

Keyword(s):

Gas Chromatography ◽

Surface Energy ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Inverse Gas Chromatography ◽

Residual Water ◽

Silica Xerogels ◽

Finite Concentration

Abstract Silylated silica xerogels, with controlled specific surface area and porosity, were prepared by a two-step procedure. In the first step, hydrogels were treated “in-situ” with hexamethyldisiloxane (HMDS) in the presence of 2-propanol and acid. In the second step, the hydrophobic gel was transferred into an organic solvent, the residual water removed by azeotropic distillation and the dried xerogel isolated by evaporating the solvent. Using this procedure, structure collapse of the hydrogels was minimized and it was possible to make xerogels with controlled specific surface area and porosity by varying the aging conditions of the hydrogels. The surface properties of both the untreated and the “in-situ” treated silica xerogels were examined by inverse gas chromatography (IGC) at either infinite dilution conditions (IGC-ID) or finite concentration conditions (IGC-FD). The former method was used to monitor the thermodynamic parameters of adsorption of molecular probes in interaction with the sites having the highest energies, while the latter method was used to provide information about the surface energy heterogeneity of the whole surface. The results for the xerogels are also compared to those obtained on untreated and silylated fumed silicas. After silylation, a systematical surface energy decrease has been observed at both ID and FD conditions of IGC for the two types of silica. However, the modified xerogels with higher surface coverage than silylated fumed silica show some different behaviors.

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Surface Energy Determined by Inverse Gas Chromatography as a Tool to Investigate Particulate Interactions in Dry Powder Inhalers

Current Pharmaceutical Design ◽

10.2174/1381612821666150820110046 ◽

2015 ◽

Vol 21 (27) ◽

pp. 3932-3944 ◽

Cited By ~ 5

Author(s):

Shyamal Das ◽

Ian Tucker ◽

Peter Stewart

Keyword(s):

Gas Chromatography ◽

Surface Energy ◽

Inverse Gas Chromatography ◽

Dry Powder Inhalers ◽

Dry Powder

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Size and surface modification of silica nanoparticles affect the severity of lung toxicity by modulating endosomal ROS generation in macrophages

Particle and Fibre Toxicology ◽

10.1186/s12989-021-00415-0 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Masahide Inoue ◽

Koji Sakamoto ◽

Atsushi Suzuki ◽

Shinya Nakai ◽

Akira Ando ◽

...

Keyword(s):

Immune Response ◽

Surface Modification ◽

Lung Injury ◽

Cellular Uptake ◽

Intratracheal Instillation ◽

Chemical Properties ◽

Raw264.7 Cells ◽

Neutrophilic Infiltration ◽

Silica Nanomaterials ◽

Physico Chemical

Abstract Background As the application of silica nanomaterials continues to expand, increasing chances of its exposure to the human body and potential harm are anticipated. Although the toxicity of silica nanomaterials is assumed to be affected by their physio-chemical properties, including size and surface functionalization, its molecular mechanisms remain unclear. We hypothesized that analysis of intracellular localization of the particles and subsequent intracellular signaling could reveal a novel determinant of inflammatory response against silica particles with different physico-chemical properties. Results We employed a murine intratracheal instillation model of amorphous silica nanoparticles (NPs) exposure to compare their in vivo toxicities in the respiratory system. Pristine silica-NPs of 50 nm diameters (50 nm-plain) induced airway-centered lung injury with marked neutrophilic infiltration. By contrast, instillation of pristine silica particles of a larger diameter (3 μm; 3 μm-plain) significantly reduced the severity of lung injury and neutrophilic infiltration, possibly through attenuated induction of neutrophil chemotactic chemokines including MIP2. Ex vivo analysis of alveolar macrophages as well as in vitro assessment using RAW264.7 cells revealed a remarkably lower cellular uptake of 3 μm-plain particles compared with 50 nm-plain, which is assumed to be the underlying mechanism of attenuated immune response. The severity of lung injury and neutrophilic infiltration was also significantly reduced after intratracheal instillation of silica NPs with an amine surface modification (50 nm-NH2) when compared with 50 nm-plain. Despite unchanged efficacy in cellular uptake, treatment with 50 nm-NH2 induced a significantly attenuated immune response in RAW264.7 cells. Assessment of intracellular redox signaling revealed increased reactive oxygen species (ROS) in endosomal compartments of RAW264.7 cells treated with 50 nm-plain when compared with vehicle-treated control. In contrast, augmentation of endosomal ROS signals in cells treated with 50 nm-NH2 was significantly lower. Moreover, selective inhibition of NADPH oxidase 2 (NOX2) was sufficient to inhibit endosomal ROS bursts and induction of chemokine expressions in cells treated with silica NPs, suggesting the central role of endosomal ROS generated by NOX2 in the regulation of the inflammatory response in macrophages that endocytosed silica NPs. Conclusions Our murine model suggested that the pulmonary toxicity of silica NPs depended on their physico-chemical properties through distinct mechanisms. Cellular uptake of larger particles by macrophages decreased, while surface amine modification modulated endosomal ROS signaling via NOX2, both of which are assumed to be involved in mitigating immune response in macrophages and resulting lung injury.

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