We have developed a highly-sensitive leakage current microsensor by using the DPPC liposome entrapping K-4[Fe(CN)(6)] solution to detect existence of biomolecules especially proteins and their dynamic conditions. In this work, the addition of guanidinium hydrochloride (GuHCl) as protein denaturant successfully obtain a prominent improvement in sensitivity by 129-fold of magnitude, although target protein, which is carbonic anhydrase from bovine ( CAB), weakly interacts with liposome under the normal condition. Moreover, we can use it to evaluate the conformation state of CAB protein such as 'Native', 'Molten-Globule' and 'Unfold' states. (C) 2009 Published by Elsevier Ltd.