Eye irritation testing of nanomaterials using the EpiOcular™ eye irritation test and the bovine corneal opacity and permeability assay

Table 2 Solid test substances ^a: Particle size in a 200 mg/mL suspension in water (applied in the BCOP assay), determined by analytical ultracentrifugation (AUC) and laser diffraction (LD)

OECD number	Test material	Particles <1000 nm [mg/mL; AUC]	Particles <100 nm [mg/mL; AUC]	D₅₀ [μm; LD]	Water solubility [AUC combined with ICP-MS / ICP-AES]
NM-100	TiO₂ pigmentary	249 ^b	8.6	0.374
NM-101	TiO₂	101	3.3	0.959
NM-102	TiO₂	13.7	0.0	1.23
NM-103	TiO₂	69.2	0.0	1.56
NM-104	TiO₂	131	0.8	1.10
NM-105	TiO₂	73.2	0.2	0.938	Wohlleben et al. [70]: Ti < 0.1 ppm
NM-110	ZnO	27.4	0.0	3.00	Wohlleben et al. [70]: Only soluble in acidic environments
NM-200	Amorphous SiO₂	11.9	0.0	11.6	OECD [71]: 2.4 ± 0.03 mmol/l (corresponding to 67 mg/L)
NM-203	Amorphous SiO₂	132	92.6	21.2	Wohlleben et al. [70]: Si: 56 ppm
NM-211	CeO₂	62.6	5.8	2.14	Wohlleben et al. [70]: CeO₂: < 0.1 ppm
NM-212	CeO₂	132	0.3	0.776	Keller et al. [72]: 0.002 wt.%
NM-400	MWCNT	14.8	0.0	383	Insoluble, supernatant fully transparent

^a For technical reasons (see text for details), ZnO NM-111 and MWCNT NM-401 and NM-402 were exempt from the characterization. Additionally, the substances that were applied undiluted in the BCOP assay were exempt from the characterization
^b The recorded value exceeds the total dose. Possibly, the refractive index increment for TiO₂ (dn/dc = 0.376 cm³/g) does not apply for TiO₂ NM-100, e.g. due to its exclusively anatase crystal structure

ISSN: 1743-8977