Biomedical Engineering Reference
In-Depth Information
reduced dimensions and the possibility of undergoing chemical or physical
modiication for an optimal incorporation of therapeutic candidates. For
example, soluble functionalised CNTs present high loading capacity of poorly
water-dispersible active drugs and antigens on the basis of their high aspect
ratio. However, despite the huge amount of synthetic procedures that have
been elaborated so far on or with CNTs, very few experimental data are
available concerning the use of such nanomaterial for the delivery of vaccines
or immunostimulants.
The basic rationale for the employment of CNTs in this context is to link
antigens to CNTs. However, once incorporated onto CNTs, several molecules
experience a decrease in their activity due to unavoidable changes on their
conformation, thus hampering a wide exploitation of this nanomaterial. In
fact, in order to induce an immune response, the incorporation of antigens
into CNTs should not affect the antigens' natural attributes, so that antibody
response can be triggered with high speciicity. At the same time, CNTs have to
demonstrate that they do not evoke any immunogenic response from the host.
In other words, they should guarantee a lack of intrinsic immunogenicity.
Pantarotto
et al.
described different methods of linking bioactive peptides
to CNTs through a stable bond, and these methods have been described in the
following paragraphs.
5
4.2.1 Fragment Condensaon of Fully Protected Pepdes
This procedure, previously reported by Goodman
et al.
,
6
was used to bind
the free amino groups present on the sidewalls of single-walled carbon
nanotubes (SWCNTs, compound
2
) (after 1,3-dipolar cycloaddition of
azomethine ylides) with the strategically protected pentapeptide KGYYG. This
peptide was added in a threefold excess upon activation with
O
-(7-aza-
N
-
hydroxybenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexaluorophosphate
(HATU) and diisopropylethylamine (DIEA) in dimethylformamide
(DMF) for
2 hours. The inal complex was isolated by repeated precipitations from a
methanol/diethyl ether mixture. The protecting groups were subsequently
removed by treating the conjugate with triluoroacetic acid (TFA) in order to
give compound
3
in good yields (Scheme 4.1).
The most challenging part was represented by the conirmation of the
successful functionalisation of the tubes with the peptide; in fact the samples
obtained could not be injected through a C
18
chromatographic column of
RP-HPLC, since they remained trapped in the pre-column system. As a
consequence, the progression of the reaction could be followed by observing
the decrease in peptide concentration of the reaction mixture at HPLC (hence
via indirect quantiication).
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