To investigate whether the bound DNA can be released from PEI 30 -SWCNT and whether one binding mode favors DNA release, we condensed an equal amount of plasmid DNA on the freshly prepared PEI 30 -SWCNT +61mV . The complexes were subjected to ethidium bromide (EtBr)-based detection in agarose gel electrophoresis. The absence of the respective DNA fragment on the gel confirmed the efficient condensation of DNA onto the PEI-SWCNT compared to the bare plasmid control (Fig. ). As an alternative to the gel assay, the PEI 30 -SWCNT +61mV -DNA (50 ng DNA and 150 ng SWCNT) complex was used as a template in a PCR reaction to amplify a fragment of DNA from the plasmid condensed on the PEI 30 -SWCNT +61mV . The results showed no amplification of the respective DNA fragment compared to proper amplification from the control plasmid (Fig. ). This confirms that the DNA bound to PEI-SWCNTs is not available to the DNA polymerase for PCR amplification.