Abstract: The present invention relates to a bioanalytical device consisting of a microwell array with microwell (2) that are filled with assay components (12, 15, 36), wherein detection probes (36) used in the assay (10) are metal nanoparticles (11, 12) or fluorescent compounds, and wherein the microwell array is connected and/or connectable to a sample that is on a flat substrate (6) to quantify the amount of a ligand (35) in the sample by using a detection mechanism. The detection mechanism is based on change in the optical properties of some of the assay components (12, 15, 36) upon contact with the ligand (35). The present invention also relates further to a method for detecting and quantifying molecules using said bioanalytical device.