Measurement of Nanoparticle Uptake by Alveolar Macrophages - Safety of Nanomaterials along Their Lifecycle - page 143

60%

A B

50%

40%

30%

20%

10%

0%

15913172125293337414549535761
Time [min]

65 69 73 77 81 85 89 93 97 101105 109 113

FIGURE 7.4 Degree of particle overlap modeled for a particle size of >5 px (>0.5 µm): The
upper curve shows the particle-covered area in the absence of overlap. The middle curve
shows the particle-covered area including overlap ( ), and the lower curve displays the

calculated rate of overlap µ 0 ( ). Insets show particles arranged with (left) and without

(right) overlap.

7.3.1.3 Gravitational Settling of ZrO 2 Nanoparticles
Within the NanoGEM project, in vitro and in vivo experiments were carried out
with differentially functionalized ZrO 2 nanoparticles, namely a pegylated (ZrO 2 -
PGA), an acrylated (ZrO 2 -Acryl), an aminated (ZrO 2 -APTS), and an acid stabilized
form (ZrO 2 -TODS) (compare surface characteristics in Table 1.2). When these ZrO 2
NP were immersed in serum-free cell culture medium, as was used for experiments
with AM (see Chapter 8), agglomeration followed by complete gravitational settling
occurred, as was revealed by particle tracking analysis of the supernatant (data not
shown). However, to compare the dose rates in vitro, the time courses of sedimen-
tation, that is, the appearance of particles at the bottom of the culture dish, were
analyzed with the program “AM tracking” (see the following). Slight differences
were found between the four types of ZrO 2 NP as is shown in Figure 7.5. Such data
have to be taken into account when toxicity data of agglomerating nanoparticles are
evaluated (cf. Teeguarden et al. 2007; Hinderliter et al. 2010). It should be stressed
that other particles used in NanoGEM such as silver and SiO 2 particles did not
agglomerate or only partially agglomerated within the observation time. An alterna-
tive method to directly observe the uptake of single particles by light microscopy is
therefore described in the last paragraph.

7.3.2 P hagoCytosis of a gglomerated n anoPartiCles
To analyze the phagocytosis of agglomerated AlOOH and CeO 2 nanoparticles by
macrophages we performed numerous sedimentation experiments in the presence of
NR8383 macrophages. Time-lapse image series were collected from up to four sites