Impedance dispersion analysis of drug-membrane interactions

摘要

Thin lipid films modified glassy carbon electrodes (GCE) were used in this work as model system for studying the interactions between two antipsychotic phenothiazine drugs, chlorpromazine and thioridazine, and the lipid fraction of the biomembranes. The lipid films on the electrode surface were obtained through the thinning of film-forming lipid solution deposited between an electrolyte phase and the working GC electrode. The effects of the drugs on the lipid film structure were investigated by electrochemical impedance spectroscopy (EIS). To characterize the electric properties of the lipid film the impedance of the working GCE is modeled with an equivalent circuit consisting of parallel capacitance C_p and resistance R_p. These capacitance and resistance are not frequency independent but could be calculated as equivalent C_p and R_p for each measured frequency of the impedance spectrum and presented as functions of the frequency f, C_p = C_p(f) and R_p= R_p(f). For the lipid films used in this work, it is demonstrated that both C_p(f) and R_p(f) are well approximated with power-law functions. This behavior implies that the impedance Z of the films could be analysed in terms of the well-known constant-phase angle element (CPE), which is often used to describe the interfacial impedance of solid working electrodes.