On the other hand, the aggregates originally present in pristine SWNTs were considered as amorphous carbon (Figure 3A), but the dramatic increase in agglomerate structures on the surface of PEI-NH-SWNTs resulted from PEI modification (Figures 2A, B and 3A,
B). Figure 2 TEM images of pristine and PEI-functionalized carbon nanotubes. The surface morphology of pristine SWNTs (A) and MWNTs (C) was compared with that of PEI-NH-SWNTs (B) and PEI-NH-MWNTs (D) by a JEOL 2000FX TEM. Bar 20 nm. Figure 3 SEM images of GSK690693 pristine and PEI-functionalized carbon nanotubes. The surface morphology of pristine SWNTs (A) and MWNTs (C) was compared with that of PEI-NH-SWNTs (B) and PEI-NH-MWNTs (D) by a JSM-6500F SEM. Bar 100 nm. FTIR spectroscopy of click here PEI-NH-CNTs Binding of PEI to SWNTs or MWNTs was analyzed by FTIR spectroscopy. The characteristic peak at 3,360 cm−1 was assigned to N-H of PEI, which was present in PEI-NH-SWNTs and PEI-NH-MWNTs, but not in pristine SWNTs or MWNTs (Figure 4). The two major peaks at 2,990 and 2,930 cm−1 in pristine SWNTs and MWNTs were contributed by sp 2 and sp 3 carbon atoms, respectively , and were shifted to 2,920 and 2,850 cm−1 in PEI-NH-SWNTs and PEI-NH-MWNTs. Finally, the band at 1,650 cm−1 in the spectra of PEI-NH-SWNTs and PEI-NH-MWNTs resulted from the bending of primary amine groups (-NH2), which was incorporated into a broad band at 1,580 cm−1 in PEI. Figure 4 FTIR spectra
of pristine and PEI-functionalized Demeclocycline carbon nanotubes.
Pristine and PEI-functionalized carbon nanotubes were analyzed by a PerkinElmer Spectrum 100 FTIR spectrometer, AZD1480 and the spectra were compared with that of pure PEI. PEI content of PEI-NH-CNTs The amount of PEI introduced to PEI-NH-CNTs during the functionalization procedure was quantified by TGA. Pure PEI degraded nearly completely at around 420°C (Figure 5). Pristine MWNTs were thermally stable up to approximately 600°C while SWNTs were relatively unstable, and weight loss was observed at temperatures over 450°C (Figure 5). The additional weight loss of PEI-NH-SWNTs and PEI-NH-MWNTs at 420°C compared to pristine carbon nanotubes was correlated directly to the mass of PEI conjugated on PEI-NH-CNTs. Consequently, the mass attributed to PEI functionalization in PEI-NH-SWNTs and PEI-NH-MWNTs was 5.08% (w/w) and 5.28% (w/w), respectively. Figure 5 TGA of pristine and PEI-functionalized carbon nanotubes. The amount of PEI introduced to PEI-NH-SWNTs (A) or PEI-NH-MWNTs (B) during the functionalization procedure was quantified by the additional weight loss of PEI-NH-SWNTs and PEI-NH-MWNTs at 420°C compared to pristine carbon nanotubes. Particle size of PEI-NH-CNTs In order to deliver siRNAs into mammalian cells, PEI-NH-CNTs must penetrate the cell membrane. The particle size of PEI-NH-CNTs may therefore be an important factor in determining transfection efficiency.