We develop a completely integrated Lab-on-Chip (LoC) for easy, rapid and cost-effective immunoassays. The pathogen sensing system is composed of a microfluidic channel surrounded by planar microcoils which are responsible for the emission and the detection of magnetic fields. The system allows the detection and quantification of superparamagnetic beads used for immunoassays in a “sandwich” antigen-antibody configuration. We successfully tested this device with different concentrations of nanoparticles and determine the limit of detection of the prototype. These results are promising and are a step toward the creation of a portable pathogen sensing device.