Assay of bacteriorhodopsin stability on polycarbonate surface by using of FTIR-ATR: a model of disk-based bioassays

Bacteriorhodopsin (BR) is a transmembrane protein which able to transport protons through cell membrane and thus converting solar energy to electrical energy. Up to now different strategies have been used to immobilize BR. In the present study the BR has been immobilized on polycarbonate surface with two different methods. The functional groups of polycarbonate were modified in two ways (sulfuric acid, PDAC and HNO3) and then the BR was immobilized on two different modified polycarbonate surfaces. The modified surfaces were characterized by ATR-FTIR and AFM techniques. Afterward the activity of bounded BR to two different modified polycarbonate surfaces was measured. Our results show that BR bounded to modified polycarbonate surface with HNO3 (nitrated polycarbonate) has higher activity in comparison to modified with sulfuric acid (electrostatically bounded BR). Also the activities of both types of Bounded BR after 10 days were measured. The results showed that unlike electrostatically bounded BR, bounding BR to nitrated polycarbonate keeps its activity after 10 days. In conclusion, nitrated polycarbonate surface is a suitable candidate due to immobilizing BR in order to manufacture of BioCDs.