Characterization of Protein-Immobilized Polystyrene Nanoparticles Using Impedance Spectroscopy

Abstract

A novel approach for characterization of non-conductive protein-immobilized nanoparticles using AC impedance spectroscopy combined with conductive atomic force microscopy was examined. As AC impedance spectroscopy can provide information on diverse electrical properties such as capacitance and inductance, it is applicable to the characterization of non-conductive substances. Several non-conductive protein-immobilized polystyrene nanoparticles were analyzed using AC impedance spectroscopy, and their impedance spectra were used as markers for nanoparticle identification. Analyses of impedance signals using an electrical circuit model established that the capacitance and inductance of each nanoparticle changed with the adsorbed protein and that impedance spectral differences were characteristic properties of the proteins. From this study, AC impedance spectroscopy was shown to be a useful tool for characterization of non-conductive nanoparticles and is expected to be applicable to the development of sensors for nanomaterials.

Capacitance Evaluation of Inorganic Core–Shell Nanoparticles with Different Shell Layers Using SPM-Combined Impedance Spectroscopy

“…20 The circuit model shown in Figure 1b was constructed based on the physical characteristics of the electrodes and nanoparticle samples. 13…”

“…AC impedance spectroscopy combined with a scanning probe microscope (SPM) is useful for investigating the electrical properties of small substances at the nanoscale. In previous studies, SPM-combined impedance spectroscopy was used to determine local electrical properties of thin films, [6][7][8][9][10] identification of biological substance at the nanometer scale, [11][12][13][14] and capacitance imaging of substances with locally different dielectric constants. 15 Results from previous studies showed that SPM-combined impedance spectroscopy would be a promising tool for characterizing non-conductive core-shell nanoparticles.…”

“…Figure 1. (a) Schematic layout of the SPM-impedance analyzer system for impedance spectroscopy of nanoparticles, (b) An electrical circuit model constructed based on the system 13. …”

Capacitance Measurement of SiO2@BSA Core–Shell Nanoparticles Using AC Impedance Spectroscopy

“…This method was exploited to characterize the capacitive properties of a thin inorganic nanoparticle layer or a polymeric thin film. [4][5][6][7] Aside from the studies noted above on non-biological substances, AC impedance spectroscopy is an attractive method for characterizing biological substances because it can collect detailed information on the electrical properties of biomolecules, although this area has been explored only a little. Biological transformations such as DNA hybridization, immunological antibody-antigen interactions, and enzymatic reactions have been clearly indicated by AC impedance spectroscopy, with significant electrical signal changes observed during those biological developments.…”

“…By varying the protein in the shell layer, the capacitance and inductance were changed such that these electrical properties could be used as tags for protein identification. 5 These studies implied that AC impedance spectroscopy combined with c-AFM is a promising tool for biomolecular characterization that allows the use of only a small amount of biological sample and that both qualitative and quantitative properties of the protein are sensitive to the AC stimuli, resulting in differences in the AC impedance spectroscopy.…”