Laboratorio de Medios e Interfases, Departamento de Bioingeniería, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, CP4000 San Miguel de Tucumán, Tucumán, Argentina.
Biosens Bioelectron. 2013 Nov 15;49:341-7. doi: 10.1016/j.bios.2013.05.043. Epub 2013 Jun 7.
The nonlinear properties of biological suspensions have been previously presented as a bulk phenomenon without the influences of the electrodes. However, some authors have showed that the behaviour of a biological suspension is due to the nonlinear characteristics of the electrode-electrolyte interface (EEI), which is modulated by the presence of yeast cells. We have developed a method, complementary to the nonlinear dielectric spectroscopy (NLDS) which is used for the study of the behaviour of EEI with resting cell suspensions of Saccharomyces cerevisiae. The method allows researchers to detect simply and quickly the voltage and frequency ranges where the metabolic activity of yeasts is detectable. This method does not replace NLDS, and aims to reduce the time during which the electrodes are exposed to corrosion by high voltages. In this paper we applied AC overpotentials (10-630 mV) with frequencies in the range from 1 to 1000 Hz. Also, we measured current harmonic distortion produced by the nonlinearity of the interface. Changes in the transfer function were observed when yeast suspension was used. Apart from the nonlinear response typical of the EEI, we also observed the biological nonlinear behaviour. The changes in the transfer functions were assessed using the overlapping index which was defined in terms of the conditional probability. The methodology was contrasted favourably with Fourier analysis. This novel strategy has the advantages of simplicity, sensitivity, reproducibility and involves basic tools such as the usual measurement of current.
先前已经提出了生物悬浮液的非线性特性是一种整体现象，而不受电极的影响。然而，一些作者已经表明，生物悬浮液的行为是由于电极-电解质界面（EEI）的非线性特性所致，而这种特性是由酵母细胞的存在所调制的。我们开发了一种方法，与用于研究静止酵母细胞悬浮液的 EEI 行为的非线性介电光谱（NLDS）互补。该方法允许研究人员简单快速地检测到可以检测到酵母代谢活性的电压和频率范围。该方法不替代 NLDS，而是旨在减少电极因高电压而暴露于腐蚀的时间。在本文中，我们施加了交流过电压（10-630 mV），频率范围为 1 至 1000 Hz。此外，我们还测量了由界面非线性引起的电流谐波失真。当使用酵母悬浮液时，观察到传递函数的变化。除了 EEI 的典型非线性响应外，我们还观察到了生物非线性行为。使用重叠指数（根据条件概率定义）评估了传递函数的变化。该方法与傅里叶分析进行了有利的对比。这种新策略具有简单、灵敏、重现性好的优点，并且涉及到电流等常用测量工具。
