Gauging the Nanotoxicity of h2D-C₂N toward Single-Stranded DNA: An in Silico Molecular Simulation Approach

Recent toxicological assessments of graphene, graphene oxides, and some other two-dimensional (2D) materials have shown them to be substantially toxic at the nanoscale, where they inhibit and eventually disrupt biological processes. These shortfalls of graphene and analogs have resulted in a quest for novel biocompatible 2D materials with minimum cytotoxicity. In this article, we demonstrate C₂N (h2D-C₂N), a newly synthesized 2D porous graphene analog, to be non-nanotoxic toward genetic materials from an "in-silico" point of view through sequence-dependent binding of different polynucleotide single-stranded DNA (ssDNA) onto it. The calculated binding energy of nucleobases and the free energy of binding of polynucleotides follow the common trait, cytosine > guanine > adenine > thymine, and are well within the limits of physisorption. Ab-initio simulations completely exclude the possibility of any chemical reaction, demonstrating purely noncovalent binding of nucleobases with C₂N through a crucial interplay between hydrogen bonding and π-stacking interactions with the surface. Further, we show that the extent of distortion inflicted upon ssDNA by C₂N is negligible. Analysis of the density of states of the nucleobase-C₂N hybrids confirms minimum electronic perturbation of the bases after adsorption. Most importantly, we demonstrate the potency of C₂N in nucleic acid transportation via reversible binding of ssDNA. The plausible use of C₂N as a template for DNA repair is illustrated through an example of C₂N-assisted complementary ssDNA winding.