Restricted binding of a model protein on C(3)N(4) nanosheets suggests an adequate biocompatibility of the nanomaterial

Recently, C(3)N(4), a carbon nitride nanomaterial, has attracted great attention in many scientific fields due to its outstanding properties. Specifically, this nanomaterial has displayed non- or low-toxicity in biological systems suggesting its excellent biocompatibility and biosafety. Nevertheless, few studies address the structural consequences from the direct interaction between C(3)N(4) and biomolecules that could imply the physical origin of its bio-effect, particularly from the molecular level. Herein, we explored the interaction of a C(3)N(4) nanosheet and a model protein, the λ-repressor protein. We found that the C(3)N(4) nanosheet has a limited influence on the structure of the λ-repressor protein, which substantiates the outstanding biocompatibility of the nanomaterial. Detailed analyses showed that upon absorption on the C(3)N(4) nanosheet, the λ-repressor protein remains located in a relatively fixed position without compromising the structural integrity of the protein. Furthermore, the protein-nanomaterial interaction is mediated by positively charged residues located on the surface of the protein and by the regional negatively charged center on the C(3)N(4) nanosheet (i.e., N-rich defects). These findings provide further molecular-level insights into the good biocompatibility of the C(3)N(4) nanomaterial and also suggest its potential usage as a protein drug delivery platform.