Electrical impedance as an indicator of microalgal cell health

Abstract

Separating specific cell phenotypes from a heterotypic mixture is a critical step in many research projects. Traditional methods usually require a large sample volume and a complex preparation process that may alter cell property during the sorting process. Here we present the use of electrical impedance as an indicator of cell health and for identifying specific microalgal phenotypes. We developed a microfluidic platform for measuring electrical impedance at different frequencies using the bacterium-sized green alga Picochlorum SE3. The cells were cultured under different salinity conditions and sampled at four different time points. Our results demonstrate the utility of electrical impedance as an indicator of cell phenotype by providing results that are consistent with known changes in cell size and physiology. Outliers in the cell data distribution are particularly useful because they represent phenotypes that have the ability to maintain size and/or membrane ionic permeability under prolonged salt stress. This suggests that our device can be used to identify and sort desired (e.g., experimentally evolved, mutant) cell phenotypes based on their electrical impedance properties.

Assessment of the electrical penetration of cell membranes using four-frequency impedance cytometry

“…For example, the conductivity of the cell membrane increases with increasing detection frequency above 1 MHz 14 , and the membrane conductivity is related to the cell viability. Sui et al 16 and Zhong et al 17 have shown that a detection frequency of 5-8 MHz is sufficient to allow current to pass through the membranes of the living cells of mammals. This conclusion is drawn from the differences in membrane conductivity between inactivated and living cells.…”

A Review of Advanced Impedance Biosensors with Microfluidic Chips for Single-Cell Analysis

“…Electrical biosensors are subdivided into potentiometric, amperometric, and impedance sensors, depending on which electrical information is measured to obtain biological information [ 2 , 3 ]. These electrical biosensing techniques have been employed in devices and systems that detect and monitor various biological materials in a range from tissues to small biomolecules such as deoxyribonucleic acid (DNA) [ 4 , 5 , 6 , 7 , 8 ]. Specially, impedance biosensors have been used to detect biological components and molecules by measuring impedance changes without requiring special labeling processing, including cells, DNA, and proteins.…”

A Squarewave-Based Multi-Frequency Impedance Analyzer Based on the Heterodyne Architecture

“…Recently, multi-frequency EISbased system have been extensively used to simultaneously probe the particle properties at different frequencies [2]- [6]. In [3], the peak of the measured signal at 500 kHz indicates cell size, while at 5 MHz shows algal membrane properties, in particular, ionic permeability. Also in [4], multi-frequency EIS is used for the discrimination of live and dead cells.…”