Table 3.

Concentrations of Ag ions in Ag ENM samples and Ag ions released after incubation in cell culture media were evaluated by ICP-MS. Ag ions in Ag ENM stock were expressed as % of total Ag in Ag ENM samples. Ag ions were isolated from Ag ENMs by (a) extraction and (b) by ultracentrifugation. Ag ions released during 24 h incubation in cell culture medium were quantified by CP-MS and expressed as percentage of the total added Ag ENMs. Results are presented as mean ± standard deviation of 3–6 replicates

	Ag ions (%) in stock		Released Ag ions after 24 h incubation in cell culture medium
	Obtained by extraction	Obtained by ultracentrifugation
Ag_Citrate	12.16 ± 5.19	8.41 ± 0.64	7.02 ± 3.27
Ag_SDS	13.81 ± 2.49	7.28 ± 2.56	6.44 ± 1.93
Ag_Disperbyk	25.72 ± 4.33	15.86 ± 0.49	5.25 ± 1.37
Ag_Tween	19.12 ± 1.93	7.72 ± 1.45	6.68 ± 1.87
Ag_Chitosan	x	14.37 ± 9.6	11.34 ± 6.37
Ag_Byk	x	13.59 ± 5.63	3.94 ± 0.04

x – Ag ion concentrations cannot be determined for the positively charged Ag ENMs using this approach