Behaviour of silver nanoparticles in simulated saliva and gastrointestinal fluids

Continuously increasing application of silver nanoparticles (AgNPs) requires information on their safety and performance under biological conditions. Assessment of AgNPs in biological systems is also related to availability of robust toxicological methods for evaluation of toxic potential of AgNPs and information on their physicochemical state. Silver nanoparticles were subjected to action of simulated saliva, gastric and intestinal fluids, appropriately supplemented with digestive enzymes pepsin or pancreatin. The behaviour of AgNPs was determined using dynamic light scattering and transmission electron microscopy, and their toxicity as well as capability to induce inflammatory reactions were assessed using reconstructed human tissue models (EpiOral, EpiGingival, EpiIntestinal). The study revealed that during exposure to the fluids, AgNPs size and morphology changed and depended on composition and pH of the respective fluid. If present, the change in terms of growth of AgNPs size occurred immediately after contact of AgNPs with the respective fluid and continued with prolonged time of contact. A pilot study on reconstituted human tissue models revealed low toxicity and inflammatory effects of AgNPs and confirmed the suitability of 3-D models for toxicological studies including bioavailability.