title: Influence of pH, particle size and crystal form on dissolution behaviour of engineered nanomaterials.
abstract: Solubility is a critical component of physicochemical characterisation of engineered nanomaterials (ENMs) and an important parameter in their risk assessments. Standard testing methodologies are needed to estimate the dissolution behaviour and biodurability (half-life) of ENMs in biological fluids. The effect of pH, particle size and crystal form on dissolution behaviour of zinc metal, ZnO and TiO2was investigated using a simple 2 h solubility assay at body temperature (37 °C) and two pH conditions (1.5 and 7) to approximately frame the pH range found in human body fluids. Time series dissolution experiments were then conducted to determine rate constants and half-lives. Dissolution characteristics of investigated ENMs were compared with those of their bulk analogues for both pH conditions. Two crystal forms of TiO2were considered: anatase and rutile. For all compounds studied, and at both pH conditions, the short solubility assays and the time series experiments consistently showed that biodurability of the bulk analogues was equal to or greater than biodurability of the corresponding nanomaterials. The results showed that particle size and crystal form of inorganic ENMs were important properties that influenced dissolution behaviour and biodurability. All ENMs and bulk analogues displayed significantly higher solubility at low pH than at neutral pH. In the context of classification and read-across approaches, the pH of the dissolution medium was the key parameter. The main implication is that pH and temperature should be specified in solubility testing when evaluating ENM dissolution in human body fluids, even for preliminary (tier 1) screening.
authors: Environmental Health Science and Research Bureau, HECSB, Health Canada, 50 Colombine Driveway, Tunney's Pasture 0803C, Ottawa, ON, K1A 0K9, Canada.
authors: M-L
authors: ML
authors: Avramescu
authors: Environmental Health Science and Research Bureau, HECSB, Health Canada, 50 Colombine Driveway, Tunney's Pasture 0803C, Ottawa, ON, K1A 0K9, Canada. pat.rasmussen@canada.ca.|Earth and Environmental Sciences Department, University of Ottawa, Ottawa, ON, K1N 6N5, Canada. pat.rasmussen@canada.ca.
authors: P E
authors: PE
authors: Rasmussen
authors: Environmental Health Science and Research Bureau, HECSB, Health Canada, 50 Colombine Driveway, Tunney's Pasture 0803C, Ottawa, ON, K1A 0K9, Canada.
authors: M
authors: M
authors: Chénier
authors: Environmental Health Science and Research Bureau, HECSB, Health Canada, 50 Colombine Driveway, Tunney's Pasture 0803C, Ottawa, ON, K1A 0K9, Canada.|Earth and Environmental Sciences Department, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
authors: H D
authors: HD
authors: Gardner
mesh_terms: D004738:Engineering; D006207:Half-Life; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D010316:Particle Size; D012995:Solubility; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide
keywords: Biodurability; Dissolution; ICP-MS; Metal oxides; Nanomaterials; Titanium dioxide; Zinc oxide