The impact of synthetic amorphous silica (E 551) on differentiated Caco-2 cells, a model for the human intestinal epithelium

Abstract

For several decades, food-grade synthetic amorphous silica (SAS) have been used as a technological additive to reduce caking of food powders. Human exposure is thus inevitable and safety concerns are taken seriously. The toxicity of silica in general and SAS in particular has been studied extensively. Overall, there is little evidence that food-grade SAS pose any health risks to humans. However, from the available data it was often not clear which type of silica was used. Accordingly, the latest report of the European food safety authority requested additional toxicity data for well-characterised "real food-grade SAS". To close this gap, we screened a panel of ten well-defined, food-grade SAS for potential adverse effects on differentiated Caco-2 cells. Precipitated and fumed SAS with low, intermediate and high specific surface area were included to determine structure-activity relationships. In a physiological dose-range up to 50 µg/ml and 48 hours of incubation, none of the materials induced adverse effects on differentiated Caco-2 cells. This held true for endpoints of acute cytotoxicity as well as epithelial specific measures of barrier integrity. These results showed that despite considerable differences in production routes and material characteristics, food-relevant SAS did not elicit acute toxicity responses in intestinal epithelial cells. strongly indicate that independent of the production process and the specific surface area, SAS materials do not induce acute toxicity after oral exposure.

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

“…For food-relevant SAS, estimated exposure doses for daily intake are 2.41 µg/cm 2 (Sohal et al 2020) or 0.02-11 µg/ cm 2 (Hempt et al 2020). According to our previous study where we modelled the delivered dose for all the SAS materials (Hempt et al 2020), the applied doses of 50 µg/ ml correspond to deposited doses of 11.8 µg/cm 2 for SIPERNAT ® 350, 10.3 µg/cm 2 for SIPERNAT ® 22 S, 7.6 µg/ cm 2 for SIPERNAT ® 160, 10 µg/cm 2 for SIPERNAT ® 50 S, 6.1 µg/cm 2 for AEROSIL ® OX50 and 1.5 µg/cm 2 for AEROSIL ® 380 F (Hempt et al 2020), which are in a realistic exposure dose range. In our study, all investigated SAS materials did not affect cell viability/metabolic activity of the intestinal co-cultures after exposure up to 50 µg/ml for 48 h. Similarly, the particle control PS-amine, which induced a slight cytotoxic response in differentiated Caco-2 monocultures (Hempt et al 2020), did not decrease cell viability in the co-cultures, presumably due to the presence of a protective mucus layer.…”

“…According to our previous study where we modelled the delivered dose for all the SAS materials (Hempt et al 2020), the applied doses of 50 µg/ ml correspond to deposited doses of 11.8 µg/cm 2 for SIPERNAT ® 350, 10.3 µg/cm 2 for SIPERNAT ® 22 S, 7.6 µg/ cm 2 for SIPERNAT ® 160, 10 µg/cm 2 for SIPERNAT ® 50 S, 6.1 µg/cm 2 for AEROSIL ® OX50 and 1.5 µg/cm 2 for AEROSIL ® 380 F (Hempt et al 2020), which are in a realistic exposure dose range. In our study, all investigated SAS materials did not affect cell viability/metabolic activity of the intestinal co-cultures after exposure up to 50 µg/ml for 48 h. Similarly, the particle control PS-amine, which induced a slight cytotoxic response in differentiated Caco-2 monocultures (Hempt et al 2020), did not decrease cell viability in the co-cultures, presumably due to the presence of a protective mucus layer. A decreased sensitivity in regards of cell viability and barrier integrity has previously been reported for other nanomaterials including silver, SiO 2 and CuO nanoparticles when comparing the results of a Caco-2 monoculture with an intestinal coculture model (Cornu et al 2020;Saez-Tenorio et al 2019;Ude et al 2019Ude et al , 2017Vila et al 2018).…”

“…These included precipitated silica produced by wet process (SIPERNAT® materials) as well as fumed silica produced by flame hydrolysis (AEROSIL® materials) (EFSA 2018a ; IPTS/EC 2007 ). An extensive characterisation of these SAS has been performed in our previous publication (Hempt et al 2020 ) and a summary of the particle characteristics is provided in Table 1 .…”

“…An extensive characterisation of these SAS has been performed in our previous publication (Hempt et al 2020 ) and a summary of the particle characteristics is provided in Table 1 .…”

“…In a previous study, we have investigated the deposited dose and acute toxicity of 10 food-grade SAS materials of commercial relevance in differentiated Caco-2 monolayers (Hempt et al 2020 ). We did not observe any considerable acute toxicity of the different SAS materials independent of the production process and the material properties.…”