A label-free photoelectrochemical biosensor for urokinase-type plasminogen activator detection based on a g-C 3 N 4 /CdS nanocomposite.

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C ₃ N ₄ /CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C ₃ N ₄ /CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL ^-1 , ranging from 1 μg mL ^-1 -0.1 pg mL ^-1 . The proposed strategy should provide a promising method for detection of other biomarkers.
(Copyright © 2018 Elsevier B.V. All rights reserved.)