A highly sensitive fluorescent biosensor for the detection of cytochrome c based on polydopamine nanotubes and exonuclease I amplification

Abstract

Cytochrome c (Cyt c), as an important biomarker, plays an important role in cell apoptosis and the mitochondrial electron transport chain. Here, we have developed a novel biosensor for a Cyt c assay based on polydopamine nanotubes (PDANTs) and an exonuclease I (Exo I) cyclic amplification strategy. The PDANTs can quickly adsorb FAM labeled Cyt c aptamer (P1) and quench its labeled fluorophore groups. When the Cyt c was introduced into the system, Cyt c can specifically bind to the FAM-labeled aptamer with high affinity and cause the recovery of the fluorescence signal due to the formation of a Cyt c-P1 complex. Exo I then could catalyze the cleavage of the aptamer sequence from the Cyt c-P1 complex and release the target Cyt c, and the released Cyt c could continue to bind to the Cyt c aptamer to achieve fluorescence signal amplification. The developed method demonstrates good sensitivity for Cyt c assays in the range from 0.01 to 100 μM with the detection limit of 0.003 μM. Moreover, the aptasensor has been successfully applied to detect Cyt c in a complex system.