The evaluation of cytotoxicity induced by exposure of the cultured cells in scaffold can be made by analysis of flow cytometry with Annexin-V and propidium iodide tests for determining apoptosis and cellular necrosis.
Cells detachment depends on cell type, you can use trypsin and then perform any cytotocicity assay. Or you can stain the cells within the scaffold using trypan blue or neutral red and count them under the microscope
Regarding the analysis of flow cytometry with A nnexin-V and propidium iodide tests; if there is no control scaffold what will be the control and how much the density of the cell that I have to seed on the scaffold if its 5 mm diameter and 2 mm thickness?