Multi-walled carbon nanotube oxidation dependent keratinocyte cytotoxicity and skin inflammation

Table 1 Carboxylated MWCNT physical characterization

MWCNT	Hydrodynamic Diameter (nm)	Polydispersity Index	Zeta Potential (mV)	C-C (sp²/sp³)	C-OH (%)	C=O (%)	HO-C=O (%)
High-COOH (Lot #1)	284.3	0.459	−42.1	0.26	13.88	7.59	19.7
Low-COOH (Lot #2)	178.5	0.268	−54.0	1.47	4.16	8.73	9.42
Pristine	> LOD^a	0.865	6.79	2.06	2.66	4.66	0

The nanoparticle suspensions of pristine, Lot #1, and Lot #2 MWCNTs were diluted in water and analyzed in a Malvern zetasizer. The hydrodynamic diameter, polydispersity index, and zeta potential are presented in the table. Also, suspensions of each nanoparticle were dried onto silicon wafers and analyzed via XPS, and information on the carbon region are presented in the table. The sp²/sp³ carbon bond ratio is the percentage of sp² carbon bonds divided by the sp³ carbon bonds on the surface and indicates the level of surface defects. The C-OH (alcohol), C=O (carbonyl), and HO-C=O (carboxyl) functional groups are all represented as a percent of total surface carbon bonds. ^a The hydrodynamic diameter for the pristine MWCNTs was above the machines limit of detection

ISSN: 1743-8977