Single-walled carbon nanotubes (SWCNTs) attract great interest in biomedical applications including drug and gene delivery. In this study, we developed a novel delivery system using SWCNTs associated with designed polycationic and amphiphilic peptides. Wrapping of SWCNTs with H-(-Lys-Trp-Lys-Gly-)7-OH [(KWKG)7] resulted in stable dispersion in water, but the composite aggregated in the buffered solution. This dispersion instability was also evident in a cell culture medium with fetal bovine serum. To improve the aqueous dispersibility, the SWCNTs-(KWKG)7 composite was further modified with polyethylene glycol (PEG) at the lysine residues via amide bond formation and the highest modification extent of 13.3% of the amino groups which corresponded to 2 PEG chains in each peptide molecule was achieved with fluorescein isothiocyanate-labeled carboxyl-PEG12. The uptake of the SWCNTs composite by A549 human lung adenocarcinoma epithelial cells was evaluated by visual observation and fluorescence activated cell sorting analysis for SWCNTs wrapped with a mixture of (KWKG)7 with PEGylation and H-(-Cys-Trp-Lys-Gly-)-OH-(KWKG)6 [CWKG(KWKG)6] labeled with fluorescent boron-dipyrromethene tetramethylrhodamine and 7-fold higher uptake comparing with SWCNTs-peptide composite without PEGylation was obtained suggesting the importance of dispersibility in addition to a cationic charge. The superior potential of SWCNTs composites assisted by polycationic and amphiphilic peptides with PEGylation was thus demonstrated.
Keywords: carbon nanotubes; complexation; dispersion; drug delivery systems; pegylation; peptides.
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