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Durham University

Department of Earth Sciences


Publication details for Prof. Claire Horwell

Pavan, C., Delle Piane, M., Gullo, M., Filippi, F., Fubini, B., Hoet, P., Horwell, C.J., Huaux, F., Lison, D., Lo Giudice, C., Martra, G., Montfort, E., Schins, R., Sulpizi, M., Wegner, K., Wyart-Remy, M., Ziemann, C. & Turci, F. (2019). The puzzling issue of silica toxicity: are silanols bridging the gaps between surface states and pathogenicity? Particle and Fibre Toxicology 16(1): 32.

Author(s) from Durham


Background: Silica continues to represent an intriguing topic of fundamental and applied research across various
scientific fields, from geology to physics, chemistry, cell biology, and particle toxicology. The pathogenic activity of
silica is variable, depending on the physico-chemical features of the particles. In the last 50 years, crystallinity and
capacity to generate free radicals have been recognized as relevant features for silica toxicity. The ‘surface’ also
plays an important role in silica toxicity, but this term has often been used in a very general way, without defining
which properties of the surface are actually driving toxicity. How the chemical features (e.g., silanols and siloxanes)
and configuration of the silica surface can trigger toxic responses remains incompletely understood.
Main body: Recent developments in surface chemistry, cell biology and toxicology provide new avenues to
improve our understanding of the molecular mechanisms of the adverse responses to silica particles. New physicochemical methods can finely characterize and quantify silanols at the surface of silica particles. Advanced
computational modelling and atomic force microscopy offer unique opportunities to explore the intimate
interactions between silica surface and membrane models or cells. In recent years, interdisciplinary research, using
these tools, has built increasing evidence that surface silanols are critical determinants of the interaction between
silica particles and biomolecules, membranes, cell systems, or animal models. It also has become clear that silanol
configuration, and eventually biological responses, can be affected by impurities within the crystal structure, or
coatings covering the particle surface. The discovery of new molecular targets of crystalline as well as amorphous
silica particles in the immune system and in epithelial lung cells represents new possible toxicity pathways. Cellular
recognition systems that detect specific features of the surface of silica particles have been identified.
Conclusions: Interdisciplinary research bridging surface chemistry to toxicology is progressively solving the
puzzling issue of the variable toxicity of silica. Further interdisciplinary research is ongoing to elucidate the intimate
mechanisms of silica pathogenicity, to possibly mitigate or reduce surface reactivity.
Keywords: Silica, Silicosis, Lung cancer, Auto-immune diseases, Surface reactivity, Silanol, Coating, Modelling,
Spectroscopy, Atomic force microscopy