ATP and ssDNA aptamer-mediated peroxidase-like activity of rGO@PDA@CeO2 nanozyme: Exosomal proteins profiling and detection at physiological pH for colorimetric sensor

Exosomes are extracellular vesicles that inherit molecular markers from their parent cells for the transfer and delivery of membrane and cytosolic molecules between cells. Exosome detection and protein profiling provide noninvasive access to disease diagnosis and treatment. The nanozyme designed in this paper contains polydopamine-functionalization of graphene oxide (rGO@PDA) units that can adsorb ssDNA aptamers and CeO 2 metal oxide nanosheet units with peroxidase activity. As auxiliary regulator, adenosine triphosphate (ATP) enhances peroxidase activity of rGO@PDA@CeO 2 under a wide range of pH (4–7.4), which breaks through the limitation that traditional nanozymes can only exhibit peroxidase activity under acidic conditions. The ssDNA aptamers, which are recognition probes of exosome, can be adsorbed on the surface of rGO@PDA by aromatic stacking, competing with ATP molecules. Thus, the ssDNA aptamer acts as the switch for colorimetric sensor to flexibly regulate the peroxidase activity of the rGO@PDA@CeO 2 under physiological conditions , and realizes sensitive detection of exosomes. This assay achieves a detection linear range of 0.46 × 10 7 –10 8 particle/mL and a limit down to 3.81 × 10 5 particles/mL. In addition, this aptasensor sensitively profiles six exosomal protein across five cell types and clinical samples, suggesting their potential in clinic diagnosis.