Scintillating Microplates for High-Throughput Studies Now Available

Tissue culture 384-well microtiter plates made from plastic that incorporates a scintillant into the base of the plate are now available for noninvasive quantitation in real-time analysis of a wide spectrum of biological reactions in cells under normal physiological conditions.

The PerkinElmer (Waltham, MA, USA) Cytostar-T microplates were designed for use with beta-emitting radiolabeled biomolecules. Radioactive decay is captured as blue light output with extraordinary signal clarity, and the signal is detectable using any plate-based scintillation counter. At the same time, the bases of the sterile and tissue culture-treated plates are transparent, enabling visualization of cells using an inverted microscope throughout the course of the experiment.

Cytostar-T plates had been available in a 96-well format, but due to demands for a high throughput solution, a 384-well version has now been released. The microplates are sterilized by gamma-irradiation and treated for adherence of cells by plasma discharge, which renders the cell attachment surface hydrophilic. Therefore, the tissue culture surface has not been coated but rather is stably modified with random functional groups covalently bound to the plastic in exactly the same manner as other disposable tissue culture ware. The plates also incorporate a design feature in the lid that minimizes the evaporation that occurs during incubation. The lid has condensation rings that reduce the risk of well-to-well contamination and, at the same time, reduces evaporation from individual wells.

Among the applications suitable for use with Cytostar-T microplates are studies of cell adhesion, cell signaling (e.g., receptor-ligand binding), cell motility, cell proliferation, normal cellular metabolism, metabolite transport, as well as drug processing (intake and efflux).

An example is a scintillation proximity assay that was designed to measure the invasion of [14C] and [35S] labeled cells through ECM (extracellular matrix) gel. In the test wells, a lower layer of ECM gel was added to form a barrier that prevented the labeled cells from reaching the scintillant-containing base plate. The labeled cells were then added in an upper layer of ECM gel, and the microplate was incubated overnight. Only cells invading the lower layer of ECM gel and gaining proximity to the scintillant generated a signal in the assay. A variety of cell lines with invasive and noninvasive phenotypes were examined, and the effects of inhibitor compounds were assessed.

The format of a CytoStar-T scinitillating microplate is readily adaptable to automated applications in high throughput screening. Meanwhile, the range of potential applications is bound only by the ingenuity and imagination of plate users.

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