RESUMO
Silver nanoparticles (AgNPs) are being employed in numerous consumer goods and applications; however, they are renowned for inducing negative cellular consequences including toxicity, oxidative stress, and an inflammatory response. Nanotoxicological outcomes are dependent on numerous factors, including physicochemical, biological, and environmental influences. Currently, NP safety evaluations are carried out in both cell-based in vitro and animal in vivo models, with poor correlation between these mechanisms. These discrepancies highlight the need for enhanced exposure environments, which retain the advantages of in vitro models but incorporate critical in vivo influences, such as fluid dynamics. This study characterized the effects of dynamic flow on AgNP behavior, cellular interactions, and oxidative stress within both adherent alveolar (A549) and suspension monocyte (U937) models. This study determined that the presence of physiologically relevant flow resulted in substantial modifications to AgNP cellular interactions and subsequent oxidative stress, as assessed via reactive oxygen species (ROS), glutathione levels, p53, NFκB, and secretion of pro-inflammatory cytokines. Within the adherent model, dynamic flow reduced AgNP deposition and oxidative stress markers by roughly 20%. However, due to increased frequency of contact, the suspension U937 cells were associated with higher NP interactions and intracellular stress under fluid flow exposure conditions. For example, the increased AgNP association resulted in a 50% increase in intracellular ROS and p53 levels. This work highlights the potential of modified in vitro systems to improve analysis of AgNP dosimetry and safety evaluations, including oxidative stress assessments.
RESUMO
Silver nanoparticles (AgNPs) are being increasingly utilized in consumer and medical applications. However, there remains conflicting reports on their safety, which are evaluated through a combination of in vitro and in vivo exposure models. These discrepancies may arise, in part, due to the inherent differences between cell-based and animal systems. It is well established that nanotoxicological effects are highly dependent on the unique physicochemical properties and behavior of the particle set, including size, surface chemistry, agglomeration, and ionic dissolution. However, recent studies have identified that these properties vary as a function of exposure environment; providing a rationale for the contradictory results between in vitro and in vivo assessments. Artificial physiological fluids are emerging as a powerful tool as they allow for the characterization of NPs in an environment which they would likely encounter in vivo, in addition to having the experimental advantages of flexibility and consistency. Here, we demonstrated that the utilization of artificial fluids provided a mechanism to assess AgNP behavior and induced bioresponses in environments that they would likely encounter in vivo. AgNPs were introduced within an alveolar-based exposure model, which included alveolar epithelial (A549) cells incubated within artificial alveolar fluid (AF). Additionally, the particles underwent extensive characterization within both AF and lysosomal fluid, which the AgNPs would encounter following cellular internalization. Following incubation in physiological environments AgNP properties were significantly modified versus a traditional media environment, including alterations to both extent of agglomeration and rate of ionic dissolution. Moreover, when A549s were exposed to AgNPs in AF, the cells displayed lower cytotoxicity and stress rates, corresponding to a fluid-dependent drop in silver ion production. This work highlights the need for enhanced in vitro models that more closely mimic in vivo exposure environments in order to capture true NP behaviors and cellular interactions.
