SERS-based immunoassay and degradation of CA19-9 mediated by gold nanowires anchored magnetic–semiconductor nanocomposites

Here, straight upward Au nanowires (NWs) were successfully grown onto Fe3O4@TiO2 matrix through a seed-mediated strategy to intensively improve its photocatalysis and SERS performances, facilitating a peculiar recyclable surface-enhanced Raman spectroscopy (SERS)-based immunoassay of CA19–9 in liquid form based on visible light irradiation. Such immunoassay was also supported by a smart heterobifunctional cross-linking agent-mediated probe of anti-CA19–9/4-MBA without metal nanoparticles. A low limit of detection of 5.65 × 10−4 IU mL−1 and a wide linear range from 1000 to 0.001 IU mL−1 were demonstrated through repeated constructing the sandwich immunostructure with only one batch of nanocomposites. Moreover, the actual levels of CA19–9 for colorectal cancer patients were readily measured by the recyclable immunoassay, the results of which are principally consistent with the conventional CLIA detection. Thus, such a green strategy of visible light-induced recyclable immunoassay could be expected to have a potential practicability in the clinical diagnoses of cancer.