Transformations of colloidal silver dietary supplements in a simulated GI tract: A key step towards determining safety and efficacy profiles

R.I. MacCuspie, K.E. Marchionda, N. Patel
Natural Immunogenics Corp,
United States

Keywords: AgNPs, nanosilver, GI tract, biological transformations, dietary supplements


Consumer products, such as colloidal silver dietary supplements, can have varying degrees of bioactivity depending upon the mixture of ions and particles, which determines their safety and efficacy profile. It is known nanosilver can undergo transformations in the gastrointestinal (GI) tract. Comparisons of well-defined materials for hypothesis testing and real world materials, such as products currently sold on the market, are often lacking. The initial particle size and surface area impacts how quickly transformations from metallic silver nanoparticles to bioactive silver ions can occur, and by simulating relevant conditions (Figure 1) these transformations can be studied. This work presents methodologies for measuring the amount of silver ions, plasmonic silver nanoparticles, and total silver concentration using routine industrial production QC measurements including atomic absorption spectroscopy, ultraviolet visible spectroscopy, and ion selective electrodes. Additionally, Transmission Electron Microscopy is employed to determine morphological changes (Figure 2). Reference to standard methods is made, including for example, NIST Special Publication NIST SP-1200-13 describes UV-vis measurements of particle concentrations enables measurements of AgNP dissolution kinetics without processing or separation, as validated by chemical analysis.[1] This work also presents examples of applications of these measurements in biologically relevant conditions by examining representative samples passing through a simulated GI tract including simulated saliva, which is then added to simulated gastric fluid, and finally added to simulated intestinal fluid. Well characterized controls include silver ions, 5 nm silver nanoparticles, and representative consumer products such as dietary supplements. By measuring the amount of bioactive silver for samples as they undergo transformations in this simulated GI tract, formulations for commercial products that maximize the amounts of bioactive silver under relevant conditions can be identified. In turn, the amount of silver consumed to achieve desired efficacy is reduced, ultimately increasing the safety profile whilst decreasing the total quantity of silver at risk for unintentional release into the environment; all by simply lowering the quantity of silver to achieve the same, if not better, effectiveness.