However, statistical significance (p < 0.01) was only observed at PEI-NH-MWNT/siGAPDH ratio of 10:1 (Figure 10). Compared to DharmaFECT, PEI-NH-SWNTs gave rise to more significant suppression

of GAPDH gene expression at a PEI-NH-SWNT/siGAPDH mass ratio of 1:1. There was no significant difference between the transfection efficiency of PEI-NH-SWNTs and PEI-NH-MWNTs except when the PEI-NH-CNT/siGAPDH ratio was 1:1 (Figure 10). These results suggest that PEI-NH-SWNTs and PEI-NH-MWNTs successfully delivered siGAPDH to HeLa-S3 cells and that the siRNA transfection efficiency of PEI-NH-SWNTs and PEI-NH-MWNTs was comparable Smad inhibitor to that of DharmaFECT. Figure 10 Relative GAPDH mRNA expression of HeLa-S3 cells transfected with PEI-NH-CNT/siGAPDH complexes. PEI-NH-SWNTs or PEI-NH-MWNTs were complexed with siGAPDH at mass Navitoclax cell line ratios of 1:1, 10:1, and 20:1 and incubated with HeLa-S3 cells to achieve a final siGAPDH concentration of 30 nM. After 48 h, the mRNA level of GAPDH was analyzed by quantitative PCR. The level of GAPDH gene suppression was quantitated to evaluate the transfection efficiency of PEI-NH-SWNTs and PEI-NH-MWNTs. Control, HeLa-S3 cells cultured in growth medium for 48 h; DharmaFECT, HeLa-S3 cells transfected with siGAPDH using DharmaFECT as transfection reagent. Error bars represent standard deviations (n ≥ 3). *p < 0.05 and **p < 0.01

compared to the control; ## p < 0.01 compared to selleck chemicals Thiamine-diphosphate kinase DharmaFECT. Discussion Previous studies have utilized a similar direct amination procedure as in this report to produce PEI-grafted MWNTs. Varkouhi et al. modified MWNTs of 9.5 nm in diameter with 25-kDa branched PEI, while Foillard et al. synthesized PEI-functionalized MWNTs with the less cytotoxic 600-Da branched PEI [21, 28]. In both studies, MWNTs were shortened by ultrasonication prior to PEI functionalization. This study applied direct amination method to both SWNTs and MWNTs but without shortening the carbon nanotubes. PEI functionalization increased the solubility of SWNTs and MWNTs

in water as well as their binding affinity for siRNAs. We removed larger aggregates of PEI-NH-SWNTs and PEI-NH-MWNTs by centrifugation [21, 28, 41] to improve their dispersity and homogeneity (Figure 1). After centrifugation, the particle size of PEI-NH-SWNTs and PEI-NH-MWNTs was decreased and was less affected by concentration (Figure 6). Surface modification of carbon nanotubes by PEI can be observed through TEM, SEM, and FTIR spectroscopy (Figures 2, 3, and 4) as well as the dramatic change in zeta potentials (Figure 7), and the amount of grafted PEI was estimated by TGA (Figure 5). Although both PEI-NH-SWNTs and PEI-NH-MWNTs caused HeLa-S3 cell deaths in a dose-dependent manner, they were less cytotoxic compared to pure PEI (Figure 9).