2.3.11. In Vitro Cell Viability Studies

The safety and tolerability of the resin materials used to fabricate the rings was tested in vitro in HeLa cells. The HeLa cell line is the most robust and widely used cell line to assess in vitro cell viability [52]. HeLa cells were plated at a density of 17,500 cells/well in 96-well opaque, flat-bottomed, white plates from Corning Inc. (Corning, NY, USA) 48 h prior to treatment. The cell lines were treated with 3D-printed small discs (Supplementary Figure S4A). Cell viability was assessed after a 48 h treatment exposure using CellTiter-Glo® Luminescent Cell Viability Assay from Promega (Madison, WI, USA) and plates were read using the Synergy 2 Multi-mode Plate Reader from BioTek Instruments (Winooski, VT, USA). The CellTiter-Glo Luminescent Cell Viability Assay is a homogeneous method to determine the number of viable cells in culture based on quantitation of the ATP present (*Renilla* luciferase units (RLU)), which signals the presence of metabolically active cells. Cells grown in growth media alone were used as controls. Cell viability was calculated as a percentage of RLU Experimental/RLU Control.
