Viability of tumour samples prior to and following tumour-on-a-chip maintenance. (a) Viability of the tissue (%) from trypan blue exclusion (n = 8). (b) Cell death (Propidium iodide flow cytometry; n = 7). (c) Absorbance of formazan product (LDH release) measured in the effluent, red arrow indicates addition of 10% lysis reagent. Normalised per mg of tissue (n = 5).