Reply to the Comment on Critical Choices in Predicting Stone Wool Biodurability: Lysosomal Fluid Compositions and Binder Effects

Dissolution Rate of Nanomaterials Determined by Ions and Particle Size under Lysosomal Conditions: Contributions to Standardization of Simulant Fluids and Analytical Methods

“…Several of the same fluids that we tested on ENM in the present study had a critical difference on MMVF in their ability to modulate the formation of Si-rich gels on the fiber surfaces. Removing the binder accelerated the average dissolution rate by +104% (max +273%) across the fluids, and this quantitative change was concomitant with a qualitative change of secondary structures, such as leaching pits, gels, collapsed bubbles, and crystalline deposits . To enhance the reliability and robustness of abiotic predictions of biodurability, Sauer et al recommended replacing the critically influential citric acid in pH 4.5 fluids by other organic acids.…”

“…Removing the binder accelerated the average dissolution rate by +104% (max +273%) across the fluids, and this quantitative change was concomitant with a qualitative change of secondary structures, such as leaching pits, gels, collapsed bubbles, and crystalline deposits. 92 To enhance the reliability and robustness of abiotic predictions of biodurability, Sauer et al recommended replacing the critically influential citric acid in pH 4.5 fluids by other organic acids. Also they recommended that future studies should consider structural transformations of the fibers, including changes in fiber length, fiber composition, and reprecipitation of gel layers.…”

Which fraction of stone wool fibre surface remains uncoated by binder? A detailed analysis by time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy

“…This was also the consensus that emerged as common point of departure for hazard assessment from a debate about critical choices in the measurement of MMVF stone wool biodurability. 18–20…”

“…This was also the consensus that emerged as common point of departure for hazard assessment from a debate about critical choices in the measurement of MMVF stone wool biodurability. [18][19][20] Follow-up experiments may advance the safer-by-design balance between mechanical robustness, durability, low dustiness, and sufficiently fast dissolution, guided by a mechanistic understanding of the binder composition and distribution.…”

“…a robust dissolution test but should simulate physiological conditions. The near-complete coating by the binder is one of the relevant factors, 9,19 and is supported by the re-analysis of MMVF surfaces by XPS aer dissolution testing: Barly et al found that, aer dissolution testing, the surfaces assimilated from any initial content of binder to a C/Si ratio of 7-10 (compared to a value (1 measured on the MMVF without binder), 8 which we interpret as indication of a universal organic-inorganic composite gel formation that is triggered by the binder, but is not directly scaling with binder content, consistent with our ndings.…”