Translocation of gold nanoparticles across the lung epithelial tissue barrier: Combining in vitro and in silico methods to substitute in vivo experiments

Table 1 Physicochemical parameters of the AuNP before and after ALICE exposure

	AuNP diameter^a	2 nm	7 nm	18 nm	46 nm	80 nm
In suspension before ALICE exposure	UV–Vis: Maximum absorption curve^b [nm]	No LSPR^h band	512	521	529	549
	UV–Vis: Diameter^c [nm]	1-2	6-7	16-18	46	80
	DLS: Hydrodynamic diameter [nm]	n.d.ⁱ	n.d.ⁱ	20.2	52.4	80.4
	DLS: Polydispersity [%]	n.d.ⁱ	n.d.ⁱ	6.2	9.7	13.1
	Surface functionalization	Citrate-THPC^j	Citrate	Citrate	Citrate	Citrate
	ζ-potential^d [mV]	−12.3 ± 0.9	−50.9 ± 1.3	−31.7 ± 1.5	−32.4 ± 1.5	−27.5 ± 2.3
After ALICE exposure	TEM: Particle diameter^e [nm]	2.5 ± 1.2^k	6.5 ± 2.3	19.6 ± 4.2	49.1 ± 10.7	85.5 ± 14.2
	TEM: Circularity^f [−]	0.46 ± 0.13	0.60 ± 0.20	0.77 ± 0.13	0.88 ± 0.05	0.86 ± 0.10
	Fraction of gold below 30 kDa in the basolateral medium^g [%]	8.80 ± 0.34	0.52 ± 0.16	<LOD^l	<LOD^l	<LOD^l

^aAuNPs were ordered by size according to the UV–Vis measurements
^bthe complete UV–Vis spectrum can be found in Additional file 1 (Figure S1)
^cdetermined as described in Haiss et al. [72] (see Methods)
^daverage zeta potential ± standard deviation (SD)
^eaverage diameter ± SD as measured by TEM (n = 161 to 259). Histograms showing the complete particle size distribution can be found in Additional file 1 (Figure S2)
^f0 corresponds to an infinitely elongated polygon; 1 corresponds to a perfect circle
^gdetermined with an A529 CML 24 h after exposure to 100 ng/cm² AuNP. Mean fraction ± SD (n = 3)
^hLSPR: localized surface plasmon resonance
ⁱnot detected (size below the LOD of the instrument)
^jTHPC: tetrakis (hydroxymethyl) phosphonium chloride
^kleft tail of the size distribution partly below the limit of detection (<0.9 nm). Hence, mean diameter was probably slightly overestimated; see also Additional file 1
^lbelow the limit of detection (LOD depends on size. Approximate LODs are 1.4 % for 18 nm, 1.2 % for 46 nm, 2.3 % for 80 nm)

ISSN: 1743-8977