The present invention relates to optical bio-disc systems and related methods and to immobilizing receptor molecules. When a sample is injected into a fluidic circuit, the target agent binds to a capture probe bound in a capture zone. A signal is generated from tags attached to a reporter probe that has specific affinity to the target agent. The assays and methods of the present invention are implemented on an optical bio-disc. The optical bio-disc includes a flow channel having capture zones and in fluid communications with a mixing chamber, and a peripheral waste reservoir. The optical bio-disc is implemented on an optical bio-disc that has information encoding format such as CD. An disc drive assembly is employed to rotate the optical bio-disc, read and process any encoded information, and analyze the samples in the flow channel of the optical bio-disc.