The construction and performance of an automated low-cost Spreeta-based prototype biosensor system for the detection of endocrine disrupting chemicals (EDCs) is described. The system consists primarily of a Spreeta miniature liquid sensor incorporated into an aluminum flow cell holder, dedicated to support a Biacore chip frame, in combination with a simple pressurized air-driven fluid system. During the optimization, a monoclonal antibody (MAb)-based immunoassay for the estrogenic compound bisphenol A (BPA) was used as a model. After the optimization two thyroxine transport protein inhibition assays for thyroid endocrine disruptors were implemented. The average noise of the system for 1 min of baseline was 1.1 microRIU (refractive index units) and it could be operated in the range of 18-22 degrees C with a minimum baseline drift (5-10 microRIU/100 min). Optimum signal to noise ratio (S/N R) was obtained using a flow cell height of 100 microm and a flow rate of 180 microl/min. The sensitivity of the Spreeta-based biosensor inhibition assays implemented (50% inhibition concentration (IC50) of 30.2 nM for BPA using MAb12 and 12.3 and 11.6 nM for thyroxine (T4) using thyroxine-binding globulin (TBG) and recombinant transthyretin (rTTR), respectively) was comparable to the sensitivity previously obtained using a Biacore 3000 (IC50 of 39.9 nM for BPA and 8.6 and 13.7 nM, respectively, for T4). The results indicate that the alternative prototype system can be used in combination with ready-to-use biosensor chip surfaces and it is potentially a useful tool for the bioeffect-related screening of EDCs.