Photoelectrochemical sandwich immunoassay of CYFRA21-1 based on In 2 O 3 /WO 3 type-II heterojunction and CdS quantum dots-polydopamine nanospheres labeling.

Using an In 2 O 3 /WO 3 type-II heterojunction modified fluorine-doped tin oxide (FTO) electrode as the photoanode and CdS quantum dots (QDs)-polydopamine nanospheres (PDA NSs) as the secondary antibody (Ab 2 ) label, the photoelectrochemistry (PEC) sandwich immunosensing of the lung cancer marker CYFRA21-1 was studied. WO 3 nanoplates were prepared by a hydrothermal method, In 2 O 3 nanoporous spheres were prepared by a hydrothermal method followed by calcination, and the In 2 O 3 /WO 3 type-II heterojunction with high PEC activity was prepared by ultrasonic mixing and cast-coating. PDA NSs with a high surface area can be loaded with abundant Ab 2 molecules and many CdS QDs with an energy level well matched with the heterojunction, so the photocurrent signal can be amplified by the formation of a sandwich immunostructure. Through the simulation experiments of photoelectrode-modified chitosan films of varying thickness, the effective transport distance of photogenerated charges is preliminarily discussed. Under the optimized conditions, the photocurrent was linear with the common logarithm of CYFRA21-1 concentration from 100 fg mL -1 to 50 ng mL -1 , with a limit of detection of 56 fg mL -1 (S/N = 3). The immunoassay of CYFRA21-1 in human serum samples gave satisfactory recovery results.