Carbon Nanofibers Have IgE Adjuvant Capacity but Are Less Potent Than Nanotubes in Promoting Allergic Airway Responses

Table 1

Selected characteristics for CNF A, B, C, and D, swCNT, mwCNT, and ufCBP. The CNF have been thoroughly characterized, reported in Jensen et al. [7]. Data for the swCNT, mwCNT, and ufCBP were previously reported in Nygaard et al. [2].

	CNF A	CNF B	CNF C	CNF D	swCNT	mwCNT	ufCBP, Printex90
Description of morphology (SEM, TEM)^a
	Aggregated particles.; Medium fraction of fibres, mainly open channel fibres	Aggregated particles.; High fraction of fibres, mainly periodically closed channel fibres	Aggregated particles.; Low fraction of fibres, mainly open channel fibres	Aggregated particles.; Medium fraction of fibres, mainly periodically-closed channel fibres	Aggregated particles.; ~50% graphitic material of arbitrary shape; ~25% swCNT; ~25% mwCNT; Open channels	Aggregated particles.; High fraction of tubes (>90%), but most are fibres with CNT aspect (the graphite layers make low angles with the channel direction). The fibres contain many defects.; Open channels	Aggregated particles. Near spherical particles whose structures are low-graphitized
Percent fibers/tubes versus other carbonous material^a
	>50%	>80%	<50%	>50%	~50%	>90%	Not relevant
Fibre/tube widths ± standard error [range] (nm)
	37.01±1.57 [11.25–108.69]^a	83.14±4.18 [18.90–302.21]^a	35.82±2.13 [14.46–185.75]^a	70.57±2.68 [18.52–286.85]^a	4.05±0.23 nm; [1.41–10.91 nm]^a	15.04±0.47 nm; [7.62–29.01 nm]^a
					1.1 nm^b	20–30 nm^b	14.3 nm^c
Fibre lengths
	Up to 10 µm^a	Up to 10 µm^a	Up to 5 µm^a	Up to 5 µm^a	0.5–100 µm^b	0.5–200 µm^b	Not relevant
Surface area (BET, m^2/g)
	103^d	61^d	124^d	56^d	543^e	140^e	321^d
Impurities
	>95% carbon^a	>95% carbon^a	>95% carbon^a	>95% carbon^a	>95% carbon^b	>95% carbon^b	>95% carbon^a
ADF-STEM^a	High number of Ni [5–500 nm] particles, some large Ti-Fe [>1 µm] particles	Traces of Ni [3–50 nm] and Ni-Fe [50–1000 nm] particles	High number of Ni [10–1000 nm] particles, traces of Cr, Fe and Ti	Traces of Ni [10–50 nm] particles	High number of impurities, mainly Co [1–20 nm], but some Fe [50–500 nm]	Lower number of impurities, mainly Ni-(Fe) [5–40 nm]	Traces
Ni^d (AAS, %)	1.29	0.070	4.97	0.036	n.a.	n.a.	<0.0003
Fe^d (AAS, %)	0.008	0.023	0.148	0.002	n.a.	n.a.	0.003
Structural defects (𝑅=𝐼D/𝐼G as determined by Raman spectroscopy)^d
	1.7	0.7	0.9	0.6	n.a.	n.a.	1.2
Endotoxin (ng/mg)^f
	<0.0066	<0.0066	<0.0066	<0.0066	0.0079	<0.0066	<0.0066
Acidity (pH)^f
	7.34	7.36	7.38	7.35	7.28	7.31	7.32

Abbreviations: ADF-STEM: annular dark field scanning transmission electron microscopy. AAS: atomic absorption spectrometer. BET: Braunauer, Emmet, and Teller method. Fe: iron. Ni: nickel. n.a.: not analyzed. SEM: scanning electron microscopy. TEM: transmission electron microscopy. 𝑅=𝐼_D/𝐼_G: intensity ratio of the first order bands G and D.
^aAuthors observation by electron microscopy. ^bSupplied by the manufacturer. ^cAccording to Renwick et al. [15]. ^dJensen et al. [7]. ^eNygaard et al. [2]. ^fLevels in supernatants after ultracentrifugation of particle suspensions. Endotoxin detection limit = 0.0066 ng/mg (0,25 EU/mL).