Superparamagnetic nanostructures coupled with a plasmonic photoelectric beacon for photoelectrochemical immunoassay

Abstract

Matrix metalloproteinase-2 (MMP-2) is an important biomarker for early cancer prediction. Herein, a robust photoelectrochemical (PEC) sandwich-type immunosensor for MMP-2 (antigen, Ag) was developed by forming an immunocomplex in the liquid phase. Using an external magnetic field, an immunocomplex comprised of superparamagnetic Fe3O4@SiO2-Ab1, target Ag, and TiO2-Ag NPs-Ab2 was readily assembled in the liquid phase with greater efficiency than traditional solid-liquid interface strategies. MMP-2 detection was carried out in pure phosphate-buffered saline (PBS), and as more target Ag was captured, more TiO2-Ag NPs tags were bridged. The enhanced photocurrent was due to the post-introduction of photoelectric beacons and the plasmonic sensitization of Ag NPs confined in TiO2, which led to the ultrasensitivity of the PEC immunoassay. The PEC immunosensor displays a high specificity and is less time-consuming, more stable, reproducible, and cheaper. This strategy provides useful information for the design of PEC biosensing platforms.