Harnessing intrinsic biophysical cellular properties for identification of algae and cyanobacteria <i>via</i> impedance spectroscopy.

Abstract

Harmful and nuisance-causing algal blooms, driven by global climatic shifts and eutrophication, present escalating risks to water security, public health, and ecosystems. Effective management of these blooms requires rapid and precise identification of cells to implement targeted intervention. Yet, existing methods are time-intensive, requiring specialized personnel and equipment. Here, we show that <i>Chlorella vulgaris</i> (green algae) and <i>Microcystis aeruginosa</i> (cyanobacteria), two dominant freshwater species globally, can be differentiated with single-cell resolution by broadband impedance spectroscopy due to the intrinsic differing biophysical character of cyanobacterial and green algal cells. Using a custom microfluidic chip with gold microelectrodes, single cells were trapped via positive dielectrophoresis and analyzed by electrical impedance spectroscopy. We show that the distinct impedance profile of <i>Microcystis</i> arises due to the presence of gas vacuoles-non-conductive air pockets, that are absent in <i>Chlorella</i>. COMSOL-based simulations confirmed that these vacuoles lower cytoplasmic conductivity and thus, can be used to discriminate species. This label-free approach paves the way for cost-effective, scalable, on-site detection of algae and cyanobacteria, offering a solution to safeguard freshwater resources and preserve global biodiversity.