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.