Furthermore, effective immobilization of proteins is essential and important in microfluidic chips to be used as immunosensors. Several methods to immobilize antibodies on the sensor chip surface have been developed, including physical adsorption, covalent binding, and specific interaction between avidin and biotin [9, 10] . However, these previous methods have limitations in terms of denaturization, extra chemical modification and random orientation. In order to overcome these issues, Brown et al. and Park et al. developed specific gold-binding polypeptide (GBP) that endows the orientation of proteins in their functional state [11, 12] . GBP shows a strong binding affinity to the gold surface without any surface modifications [13] [14] [15] . Therefore, GBP-fusion proteins could be selectively and functionally immobilized onto the gold surface.