Biomedical Engineering Reference
In-Depth Information
An exception to this common trend is represented by the work by
Monteiro-Riviere and collaborators, who investigated whether MWCNTs were
able to cross the external membrane of human embryo kidney cells (HEK293)
and affect the cell functions. It was shown that pristine MWCNTs were able
to enter HEK293 cells and to induce the release of the proinlammatory
cytokine IL-8.
25
In addition, it was observed that they were less harmful
towards T lymphocytes than to chemically functionalised tubes.
6
The authors
speculated that such result was due to the fact that oxidised MWCNTs were
better dispersed in aqueous solution, determining higher weight/volume
concentrations and, thus, a deeper impact on toxicity. At the dose of 400
μ
g/
mL, oxidised tubes killed more than 80% of cells in 5 days, while pristine
MWCNTs decreased the cell viability of less than 40%. However, although
concentration could not be ascertained as the only parameter involved in
the cytotoxic effect, the dose used in this study was very high, and the same
experiments with concentrations inferior to 40
μ
g/mL did not affect the
function of T cells.
6
8.2.2 CNTs' Concentraon
CNTs' cytotoxic proile is not yet well elucidated, since different studies have
shown contradictory results.
26,27
The disparity could be ascribed to different
cell viability methods, cell lines and sources of CNTs. Despite this degree
of uncertainty, there is a common agreement regarding a concentration-
dependent toxicity for all nanomaterials, in the form of a direct correlation
between cell loss and doses used. More precisely, the higher the concentration
of the nanosystems incubated with cells, the more remarkable the cell
loss.
11,24,28
In the study by Sayes and Ausman, although a dose-response
relationship of toxicity in the considered range of concentrations (0.003-30
mg/mL) was observed, cell death did not exceed 50% in all cases, apart from
one in which 1% surfactant was employed. This could be attributed to the
surfactant that was coated on the surface of the nanotubes in a non-covalent,
reversible way; hence it could have been removed in the conditions of the
biological tests.
Table 8.1
summarises the most recent
in vitro
studies and the
concentrations used.
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