Why does the hemolytic activity of silica predict its pro-inflammatory activity?

Table 1 Main physico-chemical characteristics and hemolytic activity of the selected silica samples

Silica	SSA (m²/g)^b	Particle size (μm)^c		Major metal impurities (% oxides)	Free radical generation^d		% Hemolysis (at 100 cm²/ml)	Ref.
		Average diameter	90% percentile		HO˙	COO˙ˉ
Qz-1	5.2	1.7 ± 0.7	2.6	Al 1.4, Fe 0.06	++	+++	++^a	[20],[47]
Qz-2	5.2	1.4 ± 0.6	2.1	Nd	Nd	Nd	+^a	[20]
Qz-3	6.1	1.7 ± 1.8	2.8	Absent	++	absent	absent	[41]
Qz-4	6.1	1.5 ± 1.0	2.5	Nd	Nd	Nd	+^a	-
VS	3.1	1.6 ± 1.2	2.7	Absent	+	absent	++^a	[20],[40]

^a+, 10-20%; ++, 35-45% hemolysis.
^bSpecific surface area (SSA) evaluated by BET (Brunauer, Emmet and Teller method).
^cDetermined by flow particle image analysis which measures the average diameter expressed as circle equivalent (CE) diameter ± SD. The 90% percentile is the value of the CE diameter below which 90% of observations falls.
^dMeasured by electron paramagnetic resonance (EPR) spectroscopy and using DMPO as a trapping agent. Hydrogen peroxide or sodium formate were used as target molecules to generate respectively hydroxyl (HO˙) or carboxyl (COO˙ˉ) radicals.
Nd: Not determined.

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