Electrospun nanofiber incorporating a binder (e.g., biotin) is used in the form of a nonwoven or composite with a substrate. The nonwoven and composite can be joined to biosensor, e.g., by binding the biotin to streptavidin and binding streptavidin to biotinylated detector, and because of the high surface area to volume of electrospun nanofiber provides increased sensitivity.