A quantitative three-dimensional bone mineralisation assay using human dental pulp stem cell spheroids

A scaffold-free 3D assay using human dental pulp stem cell spheroids quantifies mineral deposition continuously at the well level, with a Z-factor of 0.627 ± 0.119.

• Why it matters: Current 3D mineralisation readouts rely on destructive, semi-quantitative staining that limits longitudinal tracking and complicates miniaturised multiwell testing. A non-destructive, quantitative alternative is needed for compound screening workflows.
• What they did: Primary Homo sapiens dental pulp stem cells were robotically seeded into 384-well plates to form one spheroid per well, then mineralisation was measured by adding BoneTag680 directly to culture and reading from below. Plate geometry and coatings were screened, and DNA content from the same wells served as a counter-screen.
• The result: In 10% FCS with osteogenic cocktail versus 1% FCS low-mineralisation, the assay window was 13.74 ± 3.29-fold across four independent plates, with 10.88% well-level coefficient of variation versus 55.81% in a commercial alternative. DNA content showed no increase in cell number under osteogenic conditions, supporting that the mineral signal is not biomass-driven.

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