Biomedical Engineering Reference
In-Depth Information
different nanomaterials regarding their interaction with one component of the lung
lining fluid, that is, SP-A, and it is interesting to note that the extremes of SiO
2
naked and SiO
2
phosphate match with
in vivo
inhalation inflammatory response
(Table 8.5). However, further investigations are necessary to elucidate the patterns of
adsorbed biomolecules from the complete lung lining fluid. Here, lessons learnt from
the nanoGEM project regarding obstacles to overcome when
in situ
characterizing
nanomaterials in the lung lining fluid (i.e., characterization of suitable biological
models or methodological improvements regarding sample preparation) represent
an important base of knowledge from which future investigations can be initiated.
4.3.5 C
onClusions
and
C
onsiderations
for
f
uture
s
tudies
As the lung is a major uptake route with a high probability for nanomaterials to enter
the body, the lung lining fluid is a highly important biological fluid to consider for
in situ
characterization of such materials. However, no model fluid samples can be
obtained that are identical with the
in vivo
composition of lung lining fluid, which is
in contrast to the bloodstream where serum or plasma is easily available. This makes
it very difficult to choose a single good and representative biological model for the
lung lining fluid. Therefore, many different models have been used so far (from
single lipids, mixed single lipids up to different complex isolated surfactant prepara-
tions). The suitability of a model depends very much on the purpose of the study.
The majority of studies deal with the impact of nanomaterials on the biophysical
function of PS, which is an important parameter to assess. There are, however, only
a few studies so far that focus on identification and mapping the binding components
of PS, and on the question how biomolecule adsorption affects properties and the
biological fate of nanomaterials. There are literally no studies so far on detailed
analysis of the biomolecular “fingerprint” of a nanomaterial in the lung lining fluid.
Successful interpretation of inhalation toxicity results and toxicity profiling will
therefore very much depend on how far we will be able to understand the interac-
tions at the bio-nano interface in the lung, which of course depends on standardized
physiological models of the lung lining fluid.
4.4
EXAMPLE/CASE STUDY: NANOMATERIAL INTERACTIONS WITH
BIOLOGICAL FLUIDS IN THE GASTROINTESTINAL TRACT
4.4.1 P
hysiologiCal
C
onsiderations
Ingestion is considered another major route for unintentional exposure of nanoma-
terials. In addition, it is also a main route for intentional uptake of nanomedicine.
The surface of the GIT is the largest epithelial surface in the human body (about
400 m
2
) and also in terms of length scale it is one of the largest organs with the GIT
being approximately 5 m long (or even up to 9 m without the muscle tonus) for a
typical male human. GIT is divided into a lower and an upper part without a precise
anatomical demarcation. After ingestion, the food passes from the mouth via the
esophagus to the stomach and then into the duodenum, small intestine, and then into
the large intestine.
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