Investigation of the Dynamic Relaxation Behavior of Biomolecules Immobilized on Metal Electrode in Time Domain

Biomolecules such as DNA immobilized on metal electrodes and non-Faradaic current was measured in buffered solution. The metal-biomolecules-liquid-metal structure can be regarded as a liquid type of capacitor. The measurement of the capacitive current, which is affected by the ions, biomolecules, and liquid in the solutions. It is interesting to investigate the charging and discharging process in time domain, which brings important information of the dynamic behavior of the whole system. In this study, double-stranded DNA (dsDNA) was immobilized on gold electrodes and the capacitive current was measured in buffer solution with a pulse stimulus. Different relation time constants were revealed for various surface modifications. The transient current of the sensor was measured in de-ionized water and in 30 mM TE buffer before dsDNA immobilized metal electrode, and in 30 mM TE buffer after dsDNA immobilized on the metal electrode, followed by different concentrations of HIV-1 RT protein, ranging from 1 aM to 100fM. This technique shows ultra-high sensitivity of the protein detection (1 aM), indicating that this technique is promising for biosensor applications.

 Figure 1 shows the schematic of device for capacitive current measurements.