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

Abstract 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.