The foundation of dielectrophoresis (DEP) as a tool for biological investigation is the use of the Clausius–Mossotti (C–M) factor to model the observed behaviour of cells experiencing DEP across a frequency range. Nevertheless, it is also the case that at lower frequencies, the DEP spectrum deviates from predictions; there exists a rise in DEP polarisability, which varies in frequency and magnitude with different cell types and medium conductivities. In order to evaluate the origin of this effect, we have studied DEP spectra from five cell types (erythrocytes, platelets, neurons, HeLa cancer cells and monocytes) in several conditions including medium conductivity and cell treatment. Our results suggest the effect manifests as a low-pass dispersion whose cut-off frequency varies with membrane conductance and capacitance as determined using the DEP spectrum; the effect also varies as a logarithm of medium conductivity and Debye length. These together suggest that the values of membrane capacitance and conductance depend not only on the impedance of the membrane itself, but also of the surrounding double layer. The amplitude of the effect in different cell types compared to the C–M factor was found to correlate with the depolarisation factors for the cells’ shapes, suggesting that this ratio may be useful as an indicator of cell shape for DEP modelling.

中文翻译：

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关于介电泳光谱中观察到的低频色散

介电泳 (DEP) 作为生物学研究工具的基础是使用克劳修斯-莫索蒂 (C-M) 因子来模拟在一定频率范围内经历 DEP 的细胞的观察到的行为。然而，在较低频率下，DEP 频谱也与预测存在偏差；DEP 极化率有所上升，其频率和幅度随细胞类型和介质电导率的不同而变化。为了评估这种效应的起源，我们研究了五种细胞类型（红细胞、血小板、神经元、HeLa 癌细胞和单核细胞）在多种条件下（包括中等电导率和细胞处理）的 DEP 光谱。我们的结果表明，该效应表现为低通色散，其截止频率随使用 DEP 谱确定的膜电导和电容而变化；该效应也随着介质电导率和德拜长度的对数而变化。这些共同表明膜电容和电导的值不仅取决于膜本身的阻抗，还取决于周围双层的阻抗。与 C-M 因子相比，不同细胞类型的效应幅度与细胞形状的去极化因子相关，表明该比率可用作 DEP 建模的细胞形状指标。