Revealing membrane potential by advanced impedance spectroscopy: theoretical and experimental aspects

• Published in: Journal of physics. Conference series 2013-01, Vol.434 (1), p.12087-4
• Main Authors: Gheorghiu, M, Bratu, D, Olaru, A, Polonschii, C, Gheorghiu, E
• Format: Article
• Language: English
• Subjects: Biodynamics; Cell membranes; Cells (biology); Charge distribution; Dispersions; Electric potential; Lipids; Low frequencies; Mathematical models; Membranes; Parameters; Permittivity; Physics; Spectrum analysis; Spherical shells; Stimuli; Toxicity; Very Low Frequencies; Vesicles
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/434/1/012087

In spite of recent advancement of novel optical and electrical techniques, availability of non-invasive, label-free methods to assess membrane potential of living cells is still an open issue. The theory linking membrane potential to the low frequency α dispersion exhibited by suspensions of spherical shelled particles (presenting a net charge distribution on the inner side of the shell) has been pioneered in our previous studies with emphasis on the permittivity spectra. We now report on both theoretical and experimental aspects showing that whereas α dispersion is related to a rather large variation exhibited by the permittivity spectrum the decrement presented by impedance magnitude spectrum is either extremely small, or occurs (for large cells) at very low frequencies (∼mHz) explaining the lack of experimental bioimpedance data on the matter. Based on the microscopic model we indicate that an appropriate design of the experiment may enable access to membrane potential as well as to other relevant parameters when investigating living cells and charged lipid vesicles. We discuss the effect on the low frequency of permittivity and impedance spectra of: I. Parameters pertaining to cell membrane i.e. (i) membrane potential, (ii) size of the cells/vesicles, (iii) conductivity; II. Conductivity of the outer medium. A novel measuring set-up has recently been developed within the International Centre of Biodynamics allowing for sensitive low frequency (∼10mHz) four point (bio)impedance assays. Its capability to test theoretical predictions is reported as well. The far reaching implications of this study applicability for life sciences (noninvasive access to the dynamics of relevant cell parameters) as well as for biosensing applications, e.g. assess the cytotoxicity of a wide range of stimuli, will be outlined.