Electrochemiluminescent determination of CYFRA21-1 serum levels using Ti-Fe–O nanotubes immunoassay

Prominent electrochemiluminescence (ECL) in Ti-Fe–O nanotube arrays (Ti-Fe–O NTs) with K 2 S 2 O 8 as the cathode coreactant is reported for the first time. Compared with pure titanium dioxide nanotubes (TiO 2 NTs), this heterojunction could effectively reduce the band gap, facilitate electronic transitions, and move the ECL potential to a positive direction. The ECL performance motivated the development of an ultrasensitive ECL immunosensor for detecting cytokeratin fragment 21–1 (CYFRA21-1). Magnetic beads loaded with conductive carbon black (CCB/MNTs) were used to efficiently quench the ECL signal of a Ti-Fe–O NTs electrode and were combined with an ECL immunoassay to realize sensitive detection of CYFRA21-1. Over a CYFRA21-1 concentration range of 1.0 pg·mL −1 ~ 100 ng·mL −1 , the change in the ECL signal was highly linear with the logarithm of the CYFRA21-1 concentration, and the limit of detection (LOD) was 0.114 pg·mL −1 . This ECL immunosensor was used to successfully determine the CYFRA21-1 content in serum. The recovery of CYFRA21-1 in actual serum was 88.6 – 104.4%, and the RSD was 1.4 – 3.0%. The coreaction solution used in this work was PBS (0.1 M, pH = 7.4) containing 0.05 M K 2 S 2 O 8 , the scanning range was −1.0 – 0 V, the photomultiplier tube (PMT) was set to 750 V, and the scanning rate was 100 mV·s −1 . Graphical abstract