Catalytic Nanomaterials by Conjugation of an Artificial Heme-Peroxidase to Amyloid Fibrils

The self-assembly of proteins and peptides into fibrillar amyloid aggregates is a highly promising route to define the next generation of functional nanomaterials. Amyloid fibrils, traditionally associated with neurodegenerative diseases, offer exceptional conformational and chemical stability and mechanical properties, and resistance to degradation. Here, we report the development of catalytic amyloid nanomaterials through the conjugation of a miniaturized artificial peroxidase (FeMC6*a) to a self-assembling amyloidogenic peptide derived from human transthyretin, TTR(105-115), whose sequence is YTIAALLSPYS. Our synthetic approach relies on fast and selective click ligation upon proper modification of both the peptide and FeMC6*a, leading to TTRLys¹⁰⁸@FeMC6*a. Mixing unmodified TTR(105-115) with TTRLys¹⁰⁸@FeMC6*a allowed the generation of enzyme-loaded amyloid fibrils, namely, FeMC6*a@fibrils. Catalytic studies, performed in aqueous solution at nearly neutral pH, using ABTS as a model substrate and H₂O₂ as the oxidizing agent revealed that the enzyme retains its catalytic activity. Moreover, the activity was found to depend on the TTRLys¹⁰⁸@FeMC6*a/unmodified TTR(105-115) peptide ratio. In particular, those with the 2:100 ratio showed the highest activity in terms of initial rates and substrate conversion among the screened nanoconjugates and compared to the freely diffusing enzyme. Finally, the newly developed nanomaterials were integrated into a flow system based on a polyvinylidene difluoride membrane filter. Within this flow-reactor, multiple reaction cycles were performed, showcasing the reusability and stability of the catalytic amyloids over extended periods, thus offering significantly improved characteristics compared to the isolated FeMC6*a in the application to a number of practical scenarios.