The application of fully monolithically-integrated Mach-Zehnder interferometer arrays fabricated by standard silicon technology to the label-free detection of analytes is introduced. Detection with the presented biosensor is based on a novel concept, the Frequency-Resolved Mach-Zehnder Interferometry (FR-MZI). In addition, a smart encapsulation based on an appropriately designed microfluidic system and performed at the wafer scale scheme for the easy delivery of the samples to be analyzed is demonstrated. Testing of the FR-MZI biosensors with model binding assays demonstrated the detection of streptavidin binding to immobilized biotin at concentrations in the sub nM range. This is the first experimental demonstration of the FR-MZI concept as well as the first demonstration of a monolithically fully-integrated MZI biosensor.