# Urazole-Functionalized Carbon Nanotubes as Artificial DNA Strands and Their In Vivo Toxicity

## TL;DR

Researchers created DNA-like carbon nanotubes that bind selectively to DNA and found them to be highly biocompatible in tests with worms.

## Contribution

Urazole-functionalized SWCNTs show strong DNA-binding selectivity and low toxicity, offering a new platform for biocompatible nanomaterials.

## Key findings

- f-SWCNT 1c with urazoles binds strongly to ss-dA25 and d(A•T) pairs, showing nucleobase selectivity.
- Under acidic conditions, f-SWCNT 1c exhibits the strongest DNA-binding affinity.
- f-SWCNT 1c shows no significant toxicity to C. elegans at 250 μg/mL, being ∼2500-fold less toxic than SWCNT–COOH.

## Abstract

Single-walled carbon nanotubes (SWCNTs) are grafted with
multiple
phenoxy–triazole–(ethylene glycol) ligands, whose terminals
are uniformly functionalized with DNA-binding moieties. Each binder
contains one to three binding sites for imidazolidin-2-one, hydantoin,
or urazole. Entwinement of these “artificial strands”
with ss- and dsDNAs forms pseudoduplex or pseudotriplex DNA structures,
respectively. The hybridization preference between the functionalized
SWCNTs (i.e., f-SWCNTs 1a–c) and ssDNA is investigated using homo-oligomers ss-dA25, ss-dT25, and ss-dC25. Results show
that ss-dA25 bound strongly to f-SWCNT 1c bearing urazoles, ss-dT25 bound exclusively
to 1c, and ss-dC25 bound selectively to 1a (imidazolidin-2-one) and 1b (hydantoin). For
the formation of pseudotriplets with duplex oligomers dA25•dT25 and dG25•dC25 at pH 7.4, d­(A•T) pairs bound strongly to 1c but weakly to 1a and 1b. Conversely, d­(G•C)
pairs bound strongly to 1a and moderately to 1b and 1c. Under acidic conditions (pH 5.4), 1c exhibits the strongest binding, while 1a and 1b show moderate affinity. These findings highlight the potent
binding capability and nucleobase selectivity of f-SWCNT 1c functionalized with urazoles. Biocompatibility
is also assessedtouch responses and thrashing assays are performed
to evaluate the ecotoxicity of shortened f-SWCNT 1c on the nervous system of C. elegans. No significant toxicity is observed up to concentrations of 250
μg/mL, with f-SWCNT 1c ∼2500-fold
less toxic than simple SWCNT–COOH. These results suggest that
the newly developed f-SWCNT 1c is not
only highly biocompatible but also holds great promise for broad biological
applications.