Analyzing the Biological Entity of Nanomaterials - Safety of Nanomaterials along Their Lifecycle - page 66

post-translational modifications), thus enabling a pattern analysis and quantification
before mass spectrometric identification (Blunk et al. 1993; Gessner et al. 2000).
However, these approaches are much more time and cost intensive. Bands from 1D
gels or spots from 2D gels can be cut out and identified via mass spectrometry.
In addition, gel-free mass spectrometric approaches have also been successfully
applied to study the nanoparticle's protein corona (Tenzer et al. 2011; Tenzer et al.
2013). Proteins may also be transferred to membranes for specific immuno-detection
(western blotting)—the disadvantage is that a specific antibody is needed and basi-
cally one may only confirm the presence of a specific protein but not identify all
bound proteins (Pitek et al. 2012). However all these approaches have advantages
and disadvantages—so ideally several of them should be combined in a complex
st rateg y.
4.1.4 B iologiCal f fluids as m odel s ystems to s tudy B io -n ano i interaCtions
The composition of the biomolecule corona of course depends on the respective
physiological compartment encountered by the nanomaterials. This means, accord-
ing to the route of uptake the nanoparticle will be covered with a different set of bio-
molecules. Furthermore, the protein corona is a highly dynamic complex, adsorbed
components will exchange over time as the nanomaterial translocates from one
compartment into another depending on the presence and affinity of the respec-
tive binding biomolecules. Regarding unintentional exposure of nanomaterials, there
are three main ports of entry for nanomaterials: the lungs, the gastrointestinal tract
(GIT), and the skin (Figure 4.1). There is plenty of data showing that intact skin is a
tight barrier, which typically prevents uptake of nanoparticles. Although uptake of
nanomaterial through the skin cannot be excluded completely, the uptake via this
barrier seems to be less relevant and will therefore not be discussed further in this
chapter.
With respect to intentional exposure (i.e., applications in nanomedicine), intra-
venous (i.v.) injection is one of the main routes to introduce nanomaterials into the
human body as well as oral and inhalative uptake, which have been mentioned
already. Here we will now focus on three main routes of entry, namely i.v. injec-
tion leading to direct access to systemic circulation, oral uptake (GI tract barrier),
and inhalation (lung barrier). For completeness it should be noted that other routes
of entry also exist (e.g., through the eyes, ears, and the nose), which will not be
covered here.
Depending on the uptake route the nanomaterial will first directly interact with
blood plasma in the case of i.v. injection, with lung lining fluid in the case of inha-
lation, or with gastric fluids in the case of oral uptake. Although possible, it is
technically very challenging to recover nanomaterials out of the body fluids to
directly access the biomolecule corona. Therefore, another approach may be the
use of simulants for nanomaterial dispersion mimicking in composition the respec-
tive body fluids such that the composition of nanomaterial biomolecule corona can
be assessed in a situation resembling the in vivo situation. In such test media, which
closely resembles the respective physiological compartment, other features such as
agglomeration can also be easily analyzed. Additionally, one should mention cell