Determination of silver nanoparticle release from antibacterial fabrics into artificial sweat

Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles

Microfluidic chip for culturing intestinal epithelial cell layers: Characterization and comparison of drug transport between dynamic and static models

Dynamic flow in vitro models are currently widely explored for their applicability in drug development research. The application of gut-on-chip models in toxicology is lagging behind. Here we report the application of a gut-on-chip model for biokinetic studies and compare the observed biokinetics of reference compounds with those obtained using a conventional static in vitro model. Intestinal epithelial Caco-2 cells were cultured on a porous membrane assembled between two glass flow chambers for the dynamic model, or on a porous membrane in a Transwell model. Confocal microscopy, lucifer yellow translocation, and alkaline phosphatase activity evaluation revealed that cells cultured in the gut-on-chip model formed tight, differentiated, polarized monolayers like in the static cultures. In the dynamic gut-on-chip model the transport of the high permeability compounds antipyrine, ketoprofen and digoxin was lower (i.e. 4.2-, 2.7- and 1.9-fold respectively) compared to the transport in the static Transwell model. The transport of the low permeability compound, amoxicillin, was similar in both the dynamic and static in vitro model. The obtained transport values of the compounds are in line with the compound Biopharmaceuticals Classification System. It is concluded that the gut-on-chip provides an adequate model for transport studies of chemicals

CFD Investigation into Influences of a Transversely and Periodically Deforming Microchannel on Shear Stress Behavior in a Gut-on-a-chip Device

Organ-on-a-chip allows dynamic microenvironment of the actual organ to be simulated in vitro. In this study, the CFD simulation is used to investigate the behaviors of fluid flow and shear stress due to the effect of a transversely deforming membrane caused by the cyclic deformation of the microchannel sidewalls in a gut-on-a-chip device. The result reveals that the shear stress varies linearly along the length of the microchannel. The average shear stress per cycle is approximately three times greater than that of the stationary microchannel. The amplitude and frequency of the cyclic deformation also significantly affect the flow and shear stress behaviors. The highly dynamic shear stress in the gut-on-a-chip device could be one of the major factors that makes this kind of device more viable than the traditional static cell culture

Human gut-on-chip as an intestinal model to predict compound absorption and toxicity

The small intestine is a crucial component of the digestive system allowing the digestion of food and absorption of nutrients to supply the body with energy to function properly. The complex anatomy and physiology of the human small intestine poses a challenge when defining alternative testing strategies to characterise intestinal absorption and toxicity. In the present thesis, the potential of an alternative in vitro gut-on-chip model with a continuous liquid flow to study intestinal absorption and toxicity was revealed. A glass-based chip was used to culture epithelial cells under the optimized dynamic conditions. Upon morphologic characterization a selected range of model compounds were used for transport studies including 17 dioxin congeners with different physicochemical properties that are well known food contaminants, and selected pharmaceuticals (i.e. antipyrine, ketoprofen, digoxin, amoxicillin) with well-known uptake profiles from traditional static in vitro models and from human in vivo studies. These studies were followed by the comparative gene expression study of cells cultured in the gut-on-chip and in Transwells and human intestinal tissues. Finally, a comparative gene expression study was performed evaluating the effects on gene expression profiles of a nanomaterial (TiO2 and ZnO) exposure in the gut-on-chip versus the Transwell model

Comparative transcriptomics of epithelial cells grown under static and microfluidic gut-on-chip conditions and benchmarked against human in vivo intestinal cells

Gut-on-chip devices enable exposure of cells to a continuous flow of culture medium, inducing shear stresses and could thus better recapitulate the in vivo human intestinal environment in an in vitro epithelial model compared to static culture methods. We aimed to study if dynamic culture conditions affect the gene expression of Caco-2 cells cultured statically or dynamically in a gut-on-chip device and how these gene expression patterns compared to that of intestinal segments in vivo. For this we applied whole genome transcriptomics. Dynamic culture conditions led to a total of 5927 differentially expressed genes (3280 upregulated and 2647 downregulated genes) compared to static culture conditions. Gene set enrichment analysis revealed upregulated pathways associated with the immune system, signal transduction and cell growth and death, and downregulated pathways associated with drug metabolism, compound digestion and absorption under dynamic culture conditions. Comparison of the in vitro gene expression data with transcriptome profiles of human in vivo duodenum, jejunum, ileum and colon tissue samples showed similarities in gene expression profiles with intestinal segments. It is concluded that both the static and the dynamic gut-on-chip model are suitable to study human intestinal epithelial responses as an alternative for animal models

Comparative transcriptomes of Caco-2 cells cultured under dynamic and static conditions following exposure to titanium dioxide and zinc oxide nanomaterials

Due to the widespread application of food-relevant inorganic nanomaterials, the gastrointestinal tract is potentially exposed to these materials. Gut-on-chip in vitro model systems are proposed for the investigation of compound toxicity as they better recapitulate the in vivo human intestinal environment than static models, due to the added shear stresses associated with the flow of medium in line with what cells experience in vivo. We aimed to compare the cellular responses of intestinal epithelial Caco-2 cells at the gene expression level upon TiO2 (E171) and ZnO (NM110) nanomaterial exposure when cultured under dynamic and static conditions. For this, we applied whole genome transcriptome analyses. Differentially expressed genes and related biological processes revealed culture condition specific responses upon exposure to TiO2 and ZnO nanomaterials. The materials had more effects on cells cultured in the gut-on-chip when compared to the static model, indicating that shear stress might be a major factor in cell susceptibility. This is the first report on application of a gut-on-chip system to evaluate cellular responses upon TiO2 and ZnO nanomaterials compared to a static system and extends current knowledge on nanomaterial-cell interactions and toxicity assessment. Dynamically cultured cells appear to be more sensitive and the gut-on-chip might thus be an attractive model to be used more extensively in the toxicological hazard characterization

Comparative transcriptomics of epithelial cells grown under static and microfluidic gut-on-chip conditions and benchmarked against human in vivo intestinal cells

Gut-on-chip devices enable exposure of cells to a continuous flow of culture medium, inducing shear stresses and could thus better recapitulate the in vivo human intestinal environment in an in vitro epithelial model compared to static culture methods. We aimed to study if dynamic culture conditions affect the gene expression of Caco-2 cells cultured statically or dynamically in a gut-on-chip device and how these gene expression patterns compared to that of intestinal segments in vivo. For this we applied whole genome transcriptomics. Dynamic culture conditions led to a total of 5927 differentially expressed genes (3280 upregulated and 2647 downregulated genes) compared to static culture conditions. Gene set enrichment analysis revealed upregulated pathways associated with the immune system, signal transduction and cell growth and death, and downregulated pathways associated with drug metabolism, compound digestion and absorption under dynamic culture conditions. Comparison of the in vitro gene expression data with transcriptome profiles of human in vivo duodenum, jejunum, ileum and colon tissue samples showed similarities in gene expression profiles with intestinal segments. It is concluded that both the static and the dynamic gut-on-chip model are suitable to study human intestinal epithelial responses as an alternative for animal models