Monitoring DNA conformation and charge regulations by plasmonic-based electrochemical impedance platform

A novel label-free plasmonic-based electrochemical impedance platform with multiple optical and electrochemical signals, including conventional surface plasmon resonance (SPR), amplitude/phase shift of ac SPR and admittance, was described in this work. We utilize conventional SPR and admittance amplitude to detect the K+ ion induced G-quadruplexes assembly. In particular, the admittance amplitude detects interfacial capacitance related to DNA conformation change, which has better performance to K+ ion than conventional SPR. Meanwhile, we demonstrate phase shift of ac SPR as a more sensitive parameter to detect charge status of DNA in different pH solutions.