Self-assembled Diphenylalanine Peptide Fibrils with Ultra-High Aspect Ratio: A Platform for Sensitive Electrochemical H2O2 Sensor

Inspired from the pathogenic process of diphenylalanine (FF) self-assembly, a key structural motif in forming Alzheimer’s β-amyloid peptide fibrils, a facile way for preparation of FF aromatic dipeptide fibrils and fabrication of an electrochemical biosensor were developed. Long persistence length FF fibrils with ultra-high aspect ratio over 1000 were obtained using cationic surfactant assisted evaporation induced self-assembly. The Cotton effects indicate a signature of dominant β-sheet arrangement and the thickness of the β-sheet monolayer is estimated to be 2.38 nm. The obvious blue-shift of intrinsic fluorescence indicates an extended H-aggregate between the phenyl rings in a parallel mode. The FF fibrils based electrochemical biosensor, taking horseradish peroxidase as a model enzyme, displayed an excellent electrocatalytic activity to the reduction of H2O2. The peak current was a linear function of concentrations ranging from 7.5×10-7 to 1.4×10-5 M, with a detection limit of 2.5×10-7 M. The apparent Michaelis-Menten constant was 7.2 μM. These results indicate that the FF fibrils with ultra-high aspect ratio providing a new and promising platform for construction of electrochemical biosensors.