BSA-Cu3(PO4)2 hybrid nanoflowers as a high-performance redox indicator for robust label-free electrochemical immunoassay

In this work, we report that copper ion-centered hybrid nanoflowers (HNFs) can directly act as high-performance redox indicator via a facile one-step coprecipitation methodology. By altering the bovine serum albumin (BSA) concentration in the coprecipitation synthesis system, the nucleation, growth and electrochemical activities of BSA-Cu 3 (PO 4 ) 2 HNFs could be well regulated. Thanks to the intrinsic redox activity and high specific surface area of BSA-Cu 3 (PO 4 ) 2 HNFs, it could be utilized not only as the direct electrochemical signal indicator, but also acted as nanocarriers for loading numerous detection antibodies, which was further employed for robust label-free electrochemical immunoassay of α-fetoprotein (AFP). This assay evaded the fussy labeling procedure and the addition of extra redox-active substances in the test solutions, greatly improved the accuracy and stability of the immunosensor. The strategy sheds light on exploring the electrochemical redox indicator, with great adaptability for the routine biosensing application. • BSA-Cu 3 (PO 4 ) 2 HNFs with tunable redox activities by optimizing BSA concentration. • Label-free immunosensor was developed using BSA-Cu 3 (PO 4 ) 2 HNF as signal indicator. • The strategy improved the accuracy and stability of the immunosensor.