摘要
In this study, non-faradaic current was measured in time domain and investigated on a DNA-immobilized electrode in concentrated salt environment for biosensor applications. The electric current was measured for 50 μs once the pulse voltage of 0.5 V was applied to the electrode. Immobilization of double-stranded DNA (dsDNA) caused the electric current increased, compared to the electrode without any immobilization. Doxorubicin, ranging from 1 pM to 1 nM, intercalated the dsDNA and caused different relaxation of the electric currents. The characteristics of electric current for different surface modification on the electrode was compared and successfully explained with the ion concentration, ion mobility, and the electric field in solution. Instead of the impedance measurement, which usually extracts parasitic parameters for biosensor applications, this study directly explains the relevance between the electric current and the behavior of molecules in solution, with the proposed model. This method can be applied to any affinity type of biosensors. The three indexes, including the current level, the total charge, and the relaxation time can be directly used as signals for detection, which is much simpler compared to other existing techniques.