Biomedical Engineering Reference
In-Depth Information
particle suspension. This procedure maintained the correct focal plane and led
to a more even distribution of particles in the chamber. Addition of particles was
achieved within 1 min. All steps were equally carried out in cell-free experiments to
study particle sedimentation.
7.2.3 P
artiCle
s
usPensions
In this study, we analyzed the sedimentation of AlOOH and CeO
2
nanoparticle
agglomerates under cell culture conditions. The primary particle size was 40 nm and
70 nm for AlOOH and CeO
2
, respectively. Further characterization data were taken
from Kroll et al. (2011) and are shown in Table 7.1. To suspend AlOOH or CeO
2
, pow-
ders were mixed into a serum-free medium at a concentration of 180 µg/mL, briefly
vortexed, and ultrasonicated for 10 s using a 3-mm probe (Vibra Cell, Sonics and
Materials, Danbury, CT) operated at 50 W. Suspensions were further diluted in the
F12-K medium to obtain concentrations as indicated in the text.
7.2.4 s
Canning
e
leCtron
m
iCrosCoPy
To view single nanoparticles, AlOOH and CeO
2
powders were suspended in double
distilled H
2
O by ultrasonication (45 µg/mL), and concentrated on 0.2-µm Teflon®
®
filters (Millipore). Agglomerates formed in the cell culture medium were enriched
on 0.45-µm carbonate filters and briefly washed with dH
2
O. All samples were air
dried, sputtered with gold (Sputter Coater S150B, Edwards, North Walsham, UK),
and examined with a Gemini DSM 982 (ZEISS, Oberkochen, Germany) operated at
15 kV.
TABLE 7.1
Particle Properties
AlOOH Nanoparticles
CeO
2
Nanoparticles
Primary particle size (nm) 40 70
Particle size, (d50) (nm) 40 40
BET (m²/g) 47 33
Density (g/cm
3
) 2.85 —
Crystallinity Orthorhombic, Böhmit-like Cerianite, cubic
Particle morphology Irregular spherical Irregular spherical
Purity (%) 82.7 99
Surface modification None None
Surface chemistry (%) O (61.6), Al (31.7), C (6.7) O (53), Ce (26), C (20), Cl (0.6)
ζ-Potential (pH 7) (mV)
34.0 (in 1 mmol KCl) 23.7 (in H
2
O)
ζ-Potential DMEM, 10% FBS (mV)
−7.6 ± 0.8 −7.3 ± 1.1
Solubility DMEM, 10% FBS (mg/kg) Al: 0.185 ± 0.012 Ce: <1
Note:
AlOOH and CeO
2
values are from Pauluhn (2009) and Kroll et al. (2011), respectively.
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