Carbon nanotubes functionalized with α-aminoisobutyric acid-containing peptide increase gene delivery efficiency in plant mitochondria

Functionalized carbon nanotubes have shown tremendous promise in the field of plant biotechnology for genetic engineering and cargo delivery; recent findings have shown that they can be delivered within specific organelles, such as mitochondria and chloroplasts, in intact plants. 2-Aminoisobutyric acid is an unnatural amino acid that promotes helical conformation and has been demonstrated to increase membrane permeability. Rational substitution of this amino acid into a mitochondrial targeting peptide induced a helical conformation that, when functionalized onto polymer-coated carbon nanotubes, conferred increased membrane permeability compared with that of the native peptide. The secondary structure was maintained on the surface and, when used to deliver pDNA, led to an increase in gene expression, suggesting that this method may be used to enhance the delivery efficiency of existing functional peptides. Induction of helical structures in peptides have been shown to increase their membrane permeability and facilitate cargo delivery applications. Our study has shown that substitution of an unnatural amino acid into a mitochondrial-targeting peptide induces a helical conformation that is maintained even after conjugation onto carbon nanotubes and confers increased membrane permeability. This led to an increase in DNA delivery efficiencies and gene expression into the mitochondria of intact plants when used as a DNA delivery system.