Impedimetric biosensor for assay of caspase-3 activity and evaluation of cell apoptosis using self-assembled biotin-phenylalanine network as signal enhancer

Abstract

This work demonstrates that the biotinylated phenylalanine (biotin-Phe) monomers can be self-assembled into biotin-Phe nanoparticle (biotin-FNP) under mild conditions. The resulting biotin-FNP could be used as the signal enhancer for the assay of caspase-3 activity and evaluation of cell apoptosis. Specifically, the biotinylated Asp-Glu-Val-Asp (DEVD)-containing peptide substrate was immobilized on a gold electrode surface as the specific caspase-3 cleavage site. Through the strong interaction between biotin and the linker of streptavidin (SA), the in situ formation of biotin-FNP networks was initiated on the electrode surface, thus resulting in a significant increase in the electron transfer resistance. However, once the peptide substrate was cleaved by caspase-3, the biotin tag would be detached from the sensor surface, thus hampering the capture of SA and the formation of biotin-FNP networks. The method was successfully utilized to monitor caspase-3 activity in HeLa cells treated by various anticancer reagents. The impedimetric biosensor holds great potential for cell apoptosis evaluation and anticancer drug discovery. Moreover, the signal amplification strategy using the self-assembled biotin-FNP networks can potentially be applied to develop novel affinity biosensors for the detection of proteins, nucleic acids and proteases.