A TiO2-nanowire/Au-nanoparticle hybrid layer, possessing nanocavities and a plasmonic metasurface, can accomplish an entire visible region absorbance, inducing remarkable photocurrent-extraction efficiency. A blood-glucose strip-like testing protocol assembled using this layer allows nondestructive quantitative alpha-fetoprotein detection in human serum under homemade visible LED illumination, indicating its potential in commercial point-of-care testing applications.