Validation and Demonstration of an Atmosphere-Temperature-pH-Controlled Stirred Batch Reactor System for Determination of (Nano)Material Solubility and Dissolution Kinetics in Physiological Simulant Lung Fluids

Abstract

In this study, we present a dissolution test system that allows for the testing of dissolution of nano- and micrometer size materials under highly controlled atmospheric composition (O2 and CO2), temperature, and pH. The system enables dissolution testing in physiological simulant fluids (here low-calcium Gamble’s solution and phagolysosomal simulant fluid) and derivation of the temporal dissolution rates and reactivity of test materials. The system was validated considering the initial dissolution rates and dissolution profiles using eight different materials (γ-Al2O3, TiO2 (NM-104 coated with Al2O3 and glycerin), ZnO (NM-110 and NM-113, uncoated; and NM-111 coated with triethoxycaprylsilane), SiO2 (NM-200—synthetic amorphous silica), CeO2 (NM-212), and bentonite (NM-600) showing high intra-laboratory repeatability and robustness across repeated testing (I, II, and III) in triplicate (replicate 1, 2, and 3) in low-calcium Gamble’s solution. A two-way repeated-measures ANOVA was used to determine the intra-laboratory repeatability in low-calcium Gamble’s solution, where Al2O3 (p = 0.5277), ZnO (NM-110, p = 0.6578), ZnO (NM-111, p = 0.0627), and ZnO (NM-113, p = 0.4210) showed statistical identical repeatability across repeated testing (I, II, and III). The dissolution of the materials was also tested in phagolysosomal simulant fluid to demonstrate the applicability of the ATempH SBR system in other physiological fluids. We further show the uncertainty levels at which dissolution can be determined using the ATempH SBR system.

Dissolution Behaviour of Metal-Oxide Nanomaterials in Various Biological Media

“…All ENMs tested displayed increased dissolution in PSF compared to Gamble ( Figure 3 ) due to the higher hydrogen ion concentration in PSF [ 42 , 43 , 44 , 46 ]. These results are in agreement with previous studies [ 22 , 69 , 70 ]. The low solubility of ZnO ENM in near-neutral Gamble (4.6%, 3.71 mg/L) observed in our study may be indicative of biodurability and accumulation in the interstitial lung environment.…”

“…Our results indicate durability (i.e., negligible solubility) for CeO 2 ENM in both simulated lung fluids; however, its solubility was slightly increased in PSF compared to Gamble ( Figure 3 , Table S8 ). This was also reported by Holmfred et al [ 70 ], who observed measurable dissolution of CeO 2 (NM-112) in PSF (0.029 × 10 −3 mg/L/h) but not in low-Ca Gamble medium. Based on its slow dissolution (t 1/2 > 1 year) in PSF, Keller et al [ 22 ] suggested that CeO 2 nanoparticle effects will be dominated by the particles, and therefore, accumulation may be of concern, which is also supported by our findings.…”

Influence of Pre-Dispersion Media on the Batch Reactor Dissolution Behavior of Al2O3 Coated TiO2 (NM-104) and Two ZnO (NM-110 and NM-111) Nanomaterials in Biologically Relevant Test Media

“…Ethanol pre-wetting and the same sonication conditions were applied for all pre-dispersion media to allow dispersion of both hydrophilic (NM-104 and NM-110) and hydrophobic (NM-111) test materials. It should be noted that all results concerning pre-dispersion in 0.05% BSA water as dispersion medium were obtained from Holmfred et al [ 6 ].…”

“…Dissolution testing was completed in an atmosphere–temperature–pH-controlled (ATempH) stirred batch reactor (SBR) system described and validated in Holmfred et al [ 6 ]. In brief, the system consists of four reactors, each coupled to an OMNIS titration system (Metrohm, Herisau, Switzerland); one batch reactor was used as a reference containing pure test medium (low-calcium Gamble’s solution or PSF), and three batch reactors were used for a test of NMs (n = 3).…”

“…In this work, we investigate the potential need to harmonize the pre-dispersion step in a protocol for short-term ( 24 h) stirred batch reactor dissolution testing. NMs are often supplied as powders, and creating liquid suspension of NMs is a step required for several analyses and tests, including size analysis (e.g., Verleysen et al [ 5 ]), dissolution testing in batch systems (Holmfred et al, [ 6 ]), and many (eco-)toxicological studies (intratracheal installation, pharyngeal aspiration, and injection) [ 7 , 8 , 9 ]. In most cases, such NM dispersions are prepared in stock suspensions [ 7 , 10 ].…”