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.