Synthetic peptide nano-1 increases the uptake of single-walled carbon nanotubes by HeLa cells

Numerous discoveries and procedures developed by the UTD BioNano Group with respect to the isolation and aqueous solubilization of single-walled carbon nanotubes have set the stage for their use in biomedical applications. The key ingredient in these works is a 29-amino acid residue peptide termed nano-1 that can coat carbon nanotubes. The work presented in this Fundamental Practicum describes the first experiments exposing mammalian cells to these coated nanotubes. First, the synthesis and characterization of dye-labeled nano-1 was achieved to permit confocal fluorescence microscopy of HeLa cells incubated with peptide-coated carbon nanotubes. Second, a modified sonication and centrifugation procedure was developed to enrich for shorter length (∼100-nm long) peptide-coated nanotubes to facilitate their entry into cells. Third, conditions whereby peptide, nanotubes, and peptide-coated nanotubes did not alter the growth characteristic of HeLa cells over the course of 4 days were determined. Fourth, Raman spectroscopy and confocal fluorescence microscopy were used to reveal that: (i) nanotubes (peptide-coated and non-coated) entered HeLa cells in a time- and metabolic-dependent fashion; (ii) that both peptide-coated and non-coated nanotubes could be detected in the cytoplasm and nucleus of cells; (iii) that higher relative ratios of uncoated nanotubes were distributed in the nucleus relative to the cytoplasm; (iv) that higher relative ratios of peptide-coated nanotubes were distributed in the cytoplasm relative to the nucleus; (v) that ∼3-fold more peptide-coated nanotubes entered the nucleus of HeLa cells relative to the non-coated nanotubes; and finally, (vi) that ∼8-fold more peptide-coated nanotubes entered the cytoplasm of HeLa cells relative to the non-coated nanotubes.