Density of surface charge is a more predictive factor of the toxicity of cationic carbon nanoparticles than zeta potential

Table 1 Physicochemical characteristics of the citric acid-based NPs investigated herein

NP	Passivation reagent	ζ-potential (mV)	Size (nm)	Hydrodynamic diameter in saline (nm)	Aggregation in culture medium	Elemental composition			Surface charge density (Q_ek)
NP	Passivation reagent	ζ-potential (mV)	Size (nm)	Hydrodynamic diameter in saline (nm)	Aggregation in culture medium	N (%)	C (%)	H (%)	(µmol/mg)
NP1	–	− 38.5 ± 1.9	28.5	24.7 ± 1.7	None	9.51	39.60	6.06	nd
NP2	DMEDA/PEG	+ 26.9 ± 1.6	16.3	17.7 ± 0.9	+	2.42	48.96	8.48	0.23
NP3	DMEDA	+ 21.0 ± 1.5	12.6	43.9 ± 2.4	++	12.77	35.64	6.99	0.78
NP4	PEHA	+ 20.6 ± 1.2	17.9	19.1 ± 2.0	None	12.32	26.89	7.35	1.35
NP5	bPEI600	+ 23.9 ± 2.0	39.5	10.1 ± 0.4	++	14.58	28.97	7.37	4.39
NP6	bPEI25k	+ 22.7 ± 0.1	19.1	7.2 ± 0.1	++	11.80	26.64	6.95	2.95

None: hydrodynamic diameter remaining less than 100 nm; +, partially aggregated (hydrodynamic diameter ranging between 100 and 500 nm); ++, highly aggregated (hydrodynamic diameter greater than 500 nm); –, not applicable; nd, not determined

ISSN: 1477-3155