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- ItemComprehensive characterization of osseous tissues from impedance measurements by effective medium approximation(New York, NY : American Inst. of Physics, 2021) Wei, Wenzuo; Shi, Fukun; Zhuang, Jie; Kolb, Juergen F.A unified mixing (UM) model was developed to derive microstructural information of trabecular bone, i.e., bone volume fraction (BV/TV), from electrical impedance spectroscopy. A distinct advantage of the UM-model over traditional methods, such as equivalent circuit models and multivariate analysis, is that the influence of both the environment (hydroxyapatite) and different inclusions (water, fat, and air) can be taken into account simultaneously. In addition, interactions between the different components such as interfacial polarization can be addressed by a dedicated fitting parameter v. Accordingly, values of BV/TV for different bone samples, e.g., including or not including water, were determined in the higher frequency range of 1-5 MHz. Results showed good agreement with experimental data obtained by micro-computer tomography. In particular, predictions for dielectric parameters that were derived for 3 and 4 MHz were found most promising for the assessment and distinction of osteopathic conditions and differences. This was shown by a clear differentiation of osseous tissues, e.g., the greater trochanter, femoral head, and femoral neck.
- ItemDiscrimination of different cell monolayers before and after exposure to nanosecond pulsed electric fields based on Cole-Cole and multivariate analysis(Bristol : IOP Publ., 2019) Shi, Fukun; Zhuang, Jie; Kolb, Juergen F.Normal and cancer cells, which were grown in monolayers, were investigated and discriminated by electrical bioimpedance spectroscopy (EBIS) before and after exposures to nanosecond pulsed electric fields (nsPEFs). Bioimpedance data were analysed with a Cole-Cole model and the principal component analysis (PCA). Normal and cancer cells could be clearly distinguished from each other either from Cole parameters (R 0, a, t) or from two dominant principal components. The trend of changes for Cole parameters indicated distinctively different post-nsPEF-effects between normal and cancer cells. PCA was also able to distinguish characteristic impedance spectra 30 min after exposures. The first principal component suggested that post-nsPEF-effects for normal cells were revealed especially at lower frequencies. The results indicated further that the extracellular resistance, which is dominated by cell-cell connections, might be an important factor with respect to selective nsPEF-effects on cancer cells that are organized in a monolayer or a tissue, respectively. Accordingly, the results support the application of EBIS as an early, non-invasive, label-free, and time-saving approach for the classification of cells to provide in particular predictive information on the success of cancer treatments with nsPEFs. © 2019 IOP Publishing Ltd.