Optical biosensors are one of the most widely used category of sensing tools due to their high detection sensitivity, immunity to parasitic electronic noise, multi-analyte capabilities and in many cases ability for label-free detection of biomolecular interactions. Amongst label-free optical sensors, those relying on silicon photonics are especially promising for developing small size devises appropriate for applications at the point-of-need, once the hybrid integration of light sources and detectors is realized in a cost and labor effective way. In this context, our work the last 10 years focuses on the development of silicon photonic chips that combine all optical components, both active and passive, onto the same substrate. The approach followed for the monolithic integration of arrays of thin silicon nitride optical waveguides, light emitting diodes and photodetectors on a single silicon chip as well as the different silicon photonic sensors realized over the years, including the one currently developed, will be presented. In addition, the application of the different silicon photonic chip versions as immunosensors for the determination of single or panels of analytes related to biodiagnostics or food safety sector will be discussed.