Sometimes imaging isn’t the best fit. Depending on your needs, a simple biochemical assay that can be run cheaply in a standard plate reader might give you the data you need, quickly and more cheaply than an equivalent imaging-based assay. In most cases, the imaging-based assay will likely give you more information but sometimes it can be a distraction and isn’t needed.

However, at some point during the drug discovery process questions arise that only an imaging assay can answer. Answering these questions is what imaging-based phenotypic drug discovery (PDD) is all about.

If you need to measure changes in intracellular levels of a particular protein (or even RNA) or determine whether a treatment or test compound induces aberrant subcellular localization then PDD is a good fit. Similarly, if you suspect that a subpopulation of cells within your primary culture is reacting differently, then imaging will be able to identify and selectively quantify the incidence and properties of that subpopulation. While flow cytometry can readily identify subpopulations and make highly multiplexed measurements, it is not well suited to analysis of adherent cells, subcellular localization or colocalization of proteins, changes in cell morphology, or cell-cell interactions.

In summary, if the area of study involves changes in subcellular distribution of protein(s), interaction with other proteins, or targeting to subcellular organelles then an imaging-based phenotypic assay is likely well-suited to provide answers. Cell-level measurements such as changes in cell shape (e.g. neurite outgrowth), interactions between cells (e.g. B and T cell interactions), or merely selective effects on subpopulations (e.g. differentiated myotubes versus non-differentiated myoblasts) are also readily studied using imaging-based phenotypic assays.

What about hybrid assays that combine phenotypic and target-centric readouts? >>>

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