3D or not 3D: a guide to assess cell viability in 3D cell systems.

Abstract

Cell viability is the primary integrative parameter used for various purposes, particularly when fabricating tissue equivalents (<i>e.g.</i>, using bioprinting or scaffolding techniques), optimizing conditions to cultivate cells, testing chemicals, drugs, and biomaterials, <i>etc.</i> Most of the conventional methods were originally designed for a monolayer (2D) culture; however, 2D approaches fail to adequately assess a tissue-engineered construct's viability and drug effects and recapitulate the host-pathogen interactions and infectivity. This study aims at revealing the influence of particular 3D cell systems' parameters such as the components' concentration, gel thickness, cell density, <i>etc.</i> on the cell viability and applicability of standard assays. Here, we present an approach to achieving adequate and reproducible results on the cell viability in 3D collagen- and fibrin-based systems using the Live/Dead, AlamarBlue, and PicoGreen assays. Our results have demonstrated that a routine precise analysis of 3D systems should be performed using a combination of at least three methods based on different cell properties, <i>e.g.</i> the metabolic activity, proliferative capacity, morphology, <i>etc.</i>