Transformation, Absorption and Toxicological Mechanisms of Silver Nanoparticles in the Gastrointestinal Tract Following Oral Exposure

Abstract

Oral exposure is known as the primary way for silver nanoparticles (AgNPs), which are commonly used as food additives or antibacterial agents in commercial products, to enter the human body. Although the health risk of AgNPs has been a concern and extensively researched over the past few decades, there are still numerous knowledge gaps that need to be filled to disclose what AgNPs experience in the gastrointestinal tract (GIT) and how they cause oral toxicity. In order to gain more insight into the fate of AgNPs in the GIT, the main gastrointestinal transformation of AgNPs, including aggregation/disaggregation, oxidative dissolution, chlorination, sulfuration, and corona formation, is first described. Second, the intestinal absorption of AgNPs is presented to show how AgNPs interact with epithelial cells and cross the intestinal barrier. Then, more importantly, we make an overview of the mechanisms underlying the oral toxicity of AgNPs in light of recent advances as well as the factors affecting the nano−bio interactions in the GIT, which have rarely been thoroughly elaborated in published literature. At last, we emphatically discuss the issues that need to be addressed in the future to answer the question "How does oral exposure to AgNPs cause detrimental effects on the human body?".

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A Novel Strategy for Visualizing, Tracing, and Measuring the Gastrointestinal Absorption of Silver Nanoparticles

“…Silver nanoparticles (AgNPs) or nanosilver, the most widely used nanoenabled antimicrobials by far, attract great attention in agrifood industry and clinical translation. [1][2][3] By 2019, over 400 products containing AgNPs were available on the European market. [4] currently available for the translocation of particulate Ag across the intestinal barrier.…”

“…Silver nanoparticles (AgNPs) or nanosilver, the most widely used nanoenabled antimicrobials by far, attract great attention in agrifood industry and clinical translation. [ 1–3 ] By 2019, over 400 products containing AgNPs were available on the European market. [ 4 ] For example, particulate Ag including AgNPs is being used in food products as the dietary supplement and food additive (E174 Ag) in Europe.…”

“…Prior to intestinal absorption, ingested AgNPs have to travel through the gastrointestinal tract (GIT) and undergo a series of abiotic and biotic transformations, including aggregation/disaggregation, oxidative dissolution, chlorination, sulfuration, and corona formation. [ 3,9,11 ] In order to investigate the gastrointestinal fate of AgNPs, plenty of studies have examined the transformation of AgNPs in artificial GIT fluids through simulating the digestion process from the mouth to the intestine. [ 12–18 ] These in vitro approaches provide an important insight into what AgNPs experience in the GIT before intestinal absorption or excretion from the body, but using simulated digestion models cannot reproduce the complex and dynamic interplay between AgNPs, microenvironment matrices, and cells in the GIT.…”