Biomedical Engineering Reference
In-Depth Information
Table 4.1 Kinetics and afinity constants for the interactions of functionalised CNTs
with ODN-CpG motifs
NH3 + Cl -
O
O
O
NH 3 + Cl -
N
O
NH
O
N
Functionalised CNTs
Compound 2a: SWCNTs
Compound 2b: MWCNTs
NH 3 + Cl -
Compound 5: SWCNTs
k on [M -1 s -1 ]
(5.19 ± 1.55) * 10 5
(1.23 ± 0.14) * 10 6
k off [s -1 ]
(2.99 ± 1.46) * 10 -3
(4.85 ± 0.35) * 10 -3
K d [M]
(5.88 ± 2.30) * 10 -9
(3.99 ± 10.66) * 10 -9
Subsequently, the immunostimulatory properties of the complexes were
tested in vitro . 24
In the irst series of experiments, both SWCNTs ( 2a and 5 ) and MWCNTs
( 2b ) were selected. However, the MWCNTs with the free amino group
demonstrated much lower afinity for ODN-CpG sequences than did SWCNTs.
The difference could be attributable to both dimension and charge distribution
of the different CNTs. It was observed that SWCNT-Lys-NH 3 + (compound 5 )
and MWCNT-NH 3 + (compound 2b ) displayed the same amount of positive
charges. However, a stronger avidity effect could have been involved, resulting
from the closer proximity of the two ammonium groups in SWCNT-Lys-NH 3 +
than MWCNT-NH 3 + and a consequent double electrostatic interaction for
ODN-CpG molecules. Therefore, SWCNTs represented the CNTs of choice for
the following experiments, in which various excess ratios of CNTs to a minimal
immunostimulatory dose of the ODN-CpG motifs were incubated with naïve
mouse splenocytes. In particular, complexes of SWNT-Lys-NH 3 + at 18:1 and
9:1 ratios over ODN-CpG increased its immunostimulatory properties by
58% and 45%, respectively, while lower ratios did not show remarkable
results. This is most probably due to the fact that a high excess of positive
charges of CNTs over ODN-CpG neutralised the negative charges of the DNA
sequences, thus minimising the repulsion effects with the negatively charged
cell membrane and promoting ODN-CpG's cellular internalisation.
4.4 IMMUNOGENICITY OF CARBON NANOTUBES
As reported in previous paragraphs, CNTs have been shown to be
advantageous as antigen-presenting systems. However, it is still necessary
to fully understand the role of functionalised CNTs in the immune response
 
Search WWH ::




Custom Search