Chemical Stability of High Aspect Ratio Nanoparticulate MoO3 in Biological Contexts

Historically, humanity has been quick to take any technological advancement and implement those improvements into our lives. Modern research has resulted in the relatively rapid creation of new man-made materials and their inclusion into industrial and household uses. However, the environmental consequences and health risks of materials are often not fully explored before economic pressures incentivize companies into implementation. One of the most well-known examples is the widespread use of asbestos in virtually all walks of daily life before its carcinogenic potential was fully detailed. Exposure to and inhalation of asbestos fibers was directly linked to the development of mesothelioma, with toxicity due to their high aspect ratio shape and recalcitrance. High aspect ratio rod-like nanoparticulate (NP) MoO3, which has found use in various chemical production and purification methods, is of interest in this historical context; when viewed under SEM, 2D NP MoO3 appears in a fibrous form similar to asbestos. Biopersistance of NP MoO3 was tested with a series of chemical stability tests in various media to determine whether the MoO3 particles have similar longevity to the very stable and persistent asbestos fibers when exposed to an inhalation pathway. Baseline comparison fluids include Nanopure water (NP) as a control, EPA Moderately Hard Water for environmental considerations, and PBS as a bulk body fluid. Roswell Park Memorial Institute (RPMI), Eagle’s Minimum Essential Media (EMEM), Leibovitz’s L-15 Media, Simulated Lung Fluid, and Simulated Phagolysosomic Fluid were tested to simulate the potential environments that NP MoO3 undergoing inhalation pathways might inhabit. Biopersistance was assessed through Dynamic Light Scattering (DLS) over time (run with concentrations of approximately 500 ppm), and DLS data indicated a range of stability that is qualified into three behaviors: dissolution, aggregation, and stability. These behavioral trends were confirmed with filtration over time experiments (at around 50 ppm) analyzed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICPAES). The data gathered indicates that at realistic concentrations NP MoO3 dissolved rapidly on a time scale of hours if not minutes, with the particles being stable only in nanopure water, which is not biologically relevant). NP MoO3 in simulated phagolysosomic fluid was found to undergo rapid aggregation. The outliers were attributed to pH effects rather than fluid composition; enzyme and protein concentration were controlled for by the addition of FBS into the cellular medium samples (RPMI, EMEM, L15) that were included. In conclusion, results showed that NP MoO3 is non-biologically persistent, often undergoing rapid dissolution in the various tested media. The potential for fiber based toxicity is extremely low, and any detrimental effects would be the result of dissolved ions or transformed species. Biological conditions (phagolysosomic fluid) were identified in which the NP MoO3 would be stable, opening up a possible research path.