Enzyme mimics based on self-assembled peptide functionalized with graphene oxide for polyethylene terephthalate degradation.

The degradation of polyethylene terephthalate (PET) has garnered notable attention owing to its widespread accumulation and the challenges associated with its breakdown. Herein, the enzyme mimics with PET-hydrolytic activity were developed by combining peptide nanofibers with graphene oxide (GO). Inspired by native enzymes, we designed self-assembled peptides that included active amino acids (serine, histidine, aspartate and tryptophan) and different hydrophobic amino acids, with a 9-fluorenylmethoxycarbonyl group at the N-terminus. Our comparison of hydrophobic amino acids revealed that their content not only influenced the higher-order assembly of peptide but also affected molecular conformation and PET degradation ability. By co-assembling two peptides with catalytic and binding sites in a 1:1 ratio, a more effective active enzyme mimic was constructed which was owning to the cooperative interactions among the active amino acids; in addition, hydrogen bonds and π-π stacking interactions were the main forces in enhancing catalytic effects. To further improve PET-hydrolytic ability, the co-assembled enzyme mimic was functionalised with GO through π-π stacking. This GO-peptide nanofiber hybrid exhibited increased PET-hydrolytic, as GO provided a hydrophobic microenvironment for substrate attraction and abundant carbon for facilitating proton transfer. The GO-peptide nanofiber hybrid as enzyme mimics will be a promising material for PET degradation.