Sepsis, one of the leading causes of death worldwide, occurs when a local microbial infection spreads into blood circulation triggering a vigorous inflammatory response. This response can result in multiple organ failure, which is usually fatal. Thus, early diagnosis is the only way to increase the survival rate. The aim of this project is the development of a multi-analyte optical label-free biosensor based on White Light Reflectance Spectroscopy (WLRS) for sepsis diagnosis through the rapid and accurate determination of a panel of three markers related to sepsis in blood serum samples. The targeted markers are C-reactive protein, procalcitonin and inteleukin-6. The simultaneous determination of these markers is essential to early sepsis diagnosis. In combination with the overall clinical picture of the patient could help to manage successfully the treatment. The main objectives of the project are the development of: a) label-free assays for the three targeted analytes that will be characterized by high accuracy and dynamic range covering not only the pathological serum concentrations but also the concentration range of healthy individuals, b) sensors capable for the simultaneous determination of the three analytes in the same sample by appropriate structuring and biofunctionalization of the biosensor surface, and c) a prototype instrument and accompanying software for the acquisition and processing of the signals obtained from the different assays and presentation to the final user in a concise and easy to interpret format. The project is realized in the frame of the PhD thesis of Mrs. Dimitra Tsounidi, who is the recipient of a Stavros Niarchos Foundation Industrial Fellowship in collaboration and with co-founding from the company ThetaMetrisis S.A. The experimental part of the thesis is performed in the Immunoassays/Immunosensors Lab of INRASTES in collaboration with the Chemistry Department of the University of Patras (Prof. Th. Christopoulos).