A Safer Formulation Concept for Flame-generated Engineered Nanomaterials

Engineering less toxic nanomaterials that maintain valuable functional properties is crucial to the sustainability of the nanotech industry. Herein, a safer formulation concept for flame-generated nanomaterials based on the encapsulation of potentially toxic nanomaterials by a biologically inert nanothin amorphous SiO2 layer was explored. The core-shell particles maintain specific properties of their core material but exhibit surface properties of their SiO2 shell. The SiO2-coating was performed using a previously developed flame spray pyrolysis (FSP) based Versatile Engineered Nanomaterial Generation System (VENGES) in which core ENMs are coated in-flight by the swirl injection of hexamethyldisoloxane (HMDSO). The versatility of the proposed SiO2-coating process was demonstrated on a number of ENMs (CeO2, Fe2O3, ZnO, Ag) marked by their prevalence in consumer products as well as their range in toxicity. Furthermore, the fundamentals of the SiO2-coating process were investigated for each ENM. State of the art analytical methods were used to assess the core material structure, composition and morphology (XRD, BET, and TEM). The coating efficiency for each ENM was also assessed by XPS and Chemisorption. Moreover, the effect of the SiO2-coating on the mobility and aggregation potential of ENMs in water, biological media and air were explored using state of the art analytical methods and instrumentation (DLS, SMPS). Finally, the effect of the SiO2 coating on the particle-cellular interactions was investigated using a variety of cellular lines (A459, THP1, and human primary monocyte-derived macrophages) and cellular toxicological assays (MTT, LDH and Live/Dead). Results confirmed that the SiO2 coating of ENMs can significantly reduce the toxicity of the the core material. This method can be scaled up by the nanotechnology industry and used to mediate environmental healh and safety issues related to flame generated ENMs.