Hybridization-induced physical changes of DNA are exploited in the development of DNA switchable surfaces for electrochemical biosensing purposes. Two types of biosensing concepts are explored, both based on the same basic switchable surface. The interface is designed so that the end-tethered DNA is able to switch from a flexible state to a rigid one upon hybridization. The first biosensing concept described is a label-free system that uses air oxidation of the interface, followed by the change in accessibility of the surface upon hybridization to detect complementary target DNA. The second is a ferrocene-labeled system exploiting the change in DNA flexibility alone. Atomic force microscopy studies of the DNA switching surface are described.