Label-Free Single Cell Viability Assay Using Laser Interference Microscopy

Abstract

Laser interference microscopy (LIM) is a promising label-free method for single-cell research applicable to cell viability assessment in the studies of mammalian cells. This paper describes the development of a sensitive and reproducible method for assessing cell viability using LIM. The method, based on associated signal processing techniques, has been developed as a result of real-time investigation in phase thickness fluctuations of viable and non-viable MCF-7 cells, reflecting the presence and absence of their metabolic activity. As evinced by the values of the variable vc, this variable determines the viability of a cell only in the attached state (vc exceeds 20 nm2 for viable attached cells). The critical value of the power spectrum slope βc of the phase thickness fluctuations equals 1.00 for attached MCF-7 cells and 0.71 for suspended cells. The slope of the phase fluctuations’ power spectrum for MCF-7 cells was determined to exceed the threshold value of βc for a living cell, otherwise the cell is dead. The results evince the power spectrum slope as the most appropriate indicator of cell viability, while the integrated evaluation criterion (vc and βc values) can be used to assay the viability of attached cells.

Measuring Single Bacterial Viability in Optical Traps with a Power Sweeping Technique

“…Abundant dyes, such as propidium iodide, rhodamine 123, fluorescein diacetate, and resazurin, are widely used to assess bacterial viability through membrane integrity, membrane potential, intracellular enzyme activity, respiration activity, and so on. − After labeling, these properties can be further detected using a microscope, a microplate reader, or flow cytometry, which enhances compatibility and convenience. Although these dye-based assays are straightforward, rapid, and sensitive, they also suffer from the concerns of cytotoxicity caused by high photochemical activity of dyes in excited states. − Owing to these drawbacks, these assays are commonly used as end-point detection, which limits the application in real-time and kinetic measurements . Thus, there is a persistent demand for a label-free method for assessing bacterial viability at a single-cell level serving as an alternative.…”