BIOMEDICAL APPLICATIONS III: DELIVERY OF IMMUNOSTIMULANTS AND VACCINES - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 97

such as IgG and IgM, adsorbed onto CNTs) were not conirmed by this study.
The same experiment, but without Ca 2+ (which blocks the classical pathway
activation by inactivating the protein C1qr2s2), was performed to investigate
the alternative pathway.
Interestingly, while HIPco-SWCNTs activated the complement via the
classical procedure (Fig. 8a) to a much higher extent than DWCNTs, the
opposite was observed for the alternative pathway, where DWCNTs were the
most activating (Fig. 8b).
On the whole, these results might provide an explanation for the inding
of Pantarotto et al. , 7 who showed enhanced anti-peptide antibody response
by utilising peptides coupled to nanotubes. However, it is important to notice
that Pantarotto and collaborators tested functionalised (chemically modiied)
nanotubes, while in the study on complement activation, pristine materials
were tested. Therefore, any comparison between these two investigations
might not be accurate. In fact, activation of human complement induced by
CNTs might be diminished or eliminated by alteration of surface chemistry.
Therefore, further experiments should be performed with modiied CNTs.
In any case, the demonstration of complement activation by CNTs might
prove to be advantageous for vaccination purposes, as it may enhance antigen-
presenting effects. On the other hand, it might also induce an inlammatory
response and even lead to the formation of granulomas, as already reported
by Lam et al . 28
In another study, Nygaard et al. 29 investigated whether SWCNTs and
MWCNTs were able to promote allergic immune reactions when given
together with the allergen ovalbumin (OVA). They also investigated the acute
inlammatory response to CNTs 24 hours after a single intranasal exposure
to the particles in the absence of the allergen. The results showed that both
SWCNTs and MWCNTs, together with OVA, increased serum levels of allergen-
speciic IgE antibodies and the secretion of Th2-associated cytokines, which
are involved in allergic responses. In general, the increased production of IgE
by nanomaterials could be attributed to other factors, including oxidative
stress, increased antigen presentation and allergen-carrying effects. 30-32
Therefore their role for the adjuvant effect of CNTs requires further studies.
Conversely, treatment with ultra-ine carbon black particles (ufCBPs, used
as positive control) increased TNF- α and IgG2a levels, following a behaviour
that was observed for MWCNTs but not for SWCNTs. Similarly, ufCBP
and MWCNTs, but not SWCNTs, induced an acute inlux of neutrophils 24
hours after a single exposure to the particles in the absence of the allergen
(Fig. 4.9).