The Effect Of Short Silica Fibers (0.3 Mu M 3.2 Mu M) On Macrophages

Silica fibers with a dimension of 0.3 mu m . 3.2 mu m(2) nm were prepared by a modified Stober synthesis as model particles. The particles were characterized by scanning electron microscopy, elemental analysis, thermogravimetry and X-ray powder diffraction. Their uptake by macrophages (THP-1 cells and NR8383 cells) was studied by confocal laser scanning microscopy and scanning electron microscopy. The uptake by cells was very high, but the silica fibers were not harmful to NR8383 cells in concentrations up to 100 mu g mL(-1). Only above 100 mu g mL(-1), significant cell toxic effects were observed, probably induced by a high dose of particles that had sedimented on the cells and led to the adverse effects. The chemotactic response as assessed by the particle-induced migration assay (PICMA) was weak in comparison to a control of agglomerated silica particles. The as-prepared fibers were fully X-ray amorphous but crystallized to beta-cristobalite after heating to 1000 degrees C and converted to alpha-cristobalite upon cooling to ambient temperature. The fibers had sintered to larger aggregates but retained their elongated primary shape. The particle cytotoxicity towards THP-1 cells was not significantly enhanced by the crystallization. (C) 2021 Elsevier B.V. All rights reserved.