Synthesis and Physicochemical Transformations of Size‐Sorted Graphene Oxide during Simulated Digestion and Its Toxicological Assessment against an In Vitro Model of the Human Intestinal Epithelium

Abstract

In the last decade, along with the increasing use of graphene oxide (GO) in various applications, there is also considerable interest in understanding its effects on human health. Only a few experimental approaches can simulate common routes of exposure, such as ingestion, due to the inherent complexity of the digestive tract. This study presents the synthesis of size‐sorted GO of sub‐micrometer‐ or micrometer‐sized lateral dimensions, its physicochemical transformations across mouth, gastric, and small intestinal simulated digestions, and its toxicological assessment against a physiologically relevant, in vitro cellular model of the human intestinal epithelium. Results from real‐time characterization of the simulated digestas of the gastrointestinal tract using multi‐angle laser diffraction and field‐emission scanning electron microscopy show that GO agglomerates in the gastric and small intestinal phase. Extensive morphological changes, such as folding, are also observed on GO following simulated digestion. Furthermore, X‐ray photoelectron spectroscopy reveals that GO presents covalently bound N‐containing groups on its surface. It is shown that the GO employed in this study undergoes reduction. Toxicological assessment of the GO small intestinal digesta over 24 h does not point to acute cytotoxicity, and examination of the intestinal epithelium under electron microscopy does not reveal histological alterations. Both sub‐micrometer‐ and micrometer‐sized GO variants elicit a 20% statistically significant increase in reactive oxygen species generation compared to the untreated control after a 6 h exposure.

Physical and chemical template-blocking strategies in the exponential amplification reaction of circulating microRNAs

“…All oligonucleotides were synthesized, purified, and purchased from Integrated DNA Technologies (Coralville, IA). The sequences used are enumerated in Table S1 [41,42]. All dilutions were prepared using ultrapure water unless otherwise stated.…”

Meta-analysis of cellular toxicity for graphene via data-mining the literature and machine learning

“…So do organs 19 , types and morphology 20 of cells. Most researches indicated that with the increase of graphene exposure dose 21 and time 22 , the viability of the treated cells decreased continuously, manifesting a toxicity change from low to high. Nevertheless, low-dose graphene may also have a hormesis effect 23 .…”

A high-throughput method to characterize the gut bacteria growth upon engineered nanomaterial treatment

“…Endotoxin-free synthesis of graphene oxide (GO) was performed according to an improved Hummers method previously presented by the authors. 14,39 Complete characterization data, including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and endotoxin and microbiological tests are presented in ESI † Table S1. Briefly, based on AFM measurements, GO was organized in single layers with a lateral size of 242 ± 118 nm and a thickness of 0.8 ± 0.1 nm.…”

“…Increasing interest has been shown in exploring the potential application of GO in the food, agriculture, biomedical, and water purification industries. 40,41 Due to the limited exposure data and available in vitro oral toxicology data, 14 250 ppm as a relatively high concentration has been decided as an upper testing limit.…”

“…8 Emerging nanotoxicology research shows that the nanoscale size of ENMs provides them unique physicochemical properties compared to bulk materials, which makes them more bioactive. 9 Although there are some recent studies documenting the adverse effects of ingested ENMs on human small intestinal epithelium, [10][11][12][13][14] much is still unknown with regard to their potential impact on the gut microbiome.…”