Catalytic Nanomaterials\nby Conjugation of an Artificial\nHeme-Peroxidase to Amyloid Fibrils

The self-assembly of proteins and peptides into fibrillar\namyloid\naggregates is a highly promising route to define the next generation\nof functional nanomaterials. Amyloid fibrils, traditionally associated\nwith neurodegenerative diseases, offer exceptional conformational\nand chemical stability and mechanical properties, and resistance to\ndegradation. Here, we report the development of catalytic amyloid\nnanomaterials through the conjugation of a miniaturized artificial\nperoxidase (FeMC6*a) to a self-assembling amyloidogenic peptide derived\nfrom human transthyretin, TTR(105–115), whose sequence is YTIAALLSPYS.\nOur synthetic approach relies on fast and selective click ligation\nupon proper modification of both the peptide and FeMC6*a, leading\nto TTRLys<sup>108</sup>@FeMC6*a. Mixing unmodified TTR(105–115)\nwith TTRLys<sup>108</sup>@FeMC6*a allowed the generation of enzyme-loaded\namyloid fibrils, namely, FeMC6*a@fibrils. Catalytic studies, performed\nin aqueous solution at nearly neutral pH, using ABTS as a model substrate\nand H<sub>2</sub>O<sub>2</sub> as the oxidizing agent revealed that\nthe enzyme retains its catalytic activity. Moreover, the activity\nwas found to depend on the TTRLys<sup>108</sup>@FeMC6*a/unmodified\nTTR(105–115) peptide ratio. In particular, those with the 2:100\nratio showed the highest activity in terms of initial rates and substrate\nconversion among the screened nanoconjugates and compared to the freely\ndiffusing enzyme. Finally, the newly developed nanomaterials were\nintegrated into a flow system based on a polyvinylidene difluoride\nmembrane filter. Within this flow-reactor, multiple reaction cycles\nwere performed, showcasing the reusability and stability of the catalytic\namyloids over extended periods, thus offering significantly improved\ncharacteristics compared to the isolated FeMC6*a in the application\nto a number of practical scenarios.