PEI is the determining factor in DNA binding to SWCNTs. To confirm that the ratio of PEI to SWCNTs used in the synthesis of the PEI-SWCNTs conjugate and delivery of the plasmid is not responsible for the low expression of the GFP signal, we synthesized DNA-PEI-SWCNT complexes with different ratios of PEIs-SWCNT (PEI 30 -SWCNTs, PEI 40 -SWCNT, and PEI 60 -SWCNT), each loaded with 100 ng of TRBO-G plasmid DNA and 300 ng of individual PEI-SWCNT, and infiltrated 100 µl of the solution into N. benthamiana leaves. We observed a low level of expression from PEI-SWCNT at all concentrations of PEI and observed leaf tissue damage with morphological changes with the two highest PEI concentrations (PEI 40 -SWCNT and PEI 60 -SWCNT), hindering proper imaging of the respective cells (Fig. ). Our results highlight the PEIinduced physical damage of tissues when used at high concentrations.