Patent ID: 8709711

Claim:
A method of measuring the fraction of viable cells in a tissue-engineered product maintained in a cell culture conditioned medium comprising: (a) taking, as a sample portion, a first percentage of the tissue engineered product containing cells and a proportional second percentage of the cell culture conditioned medium; (b) detecting a cell death-stable enzyme activity (Y) in a portion of a cell culture conditioned medium not containing cells of the tissue-engineered product from the sample portion taken in step (a); (c) disrupting the membrane integrity of the cells in the sample portion of the tissue engineered product taken in step (a); (d) detecting a cell death-stable enzyme activity (X) in the cells and conditioned medium of the sample portion of the tissue-engineered product taken in step (a); and (e) (i) when the ratio of the first percentage to the second percentage is 1:1, calculating the fraction of viable cells by comparing the level of cell death-stable enzyme activity detected in steps (b) and (d) according to the formula: X - cY X + Y wherein c = 1 - f f and f is the fraction of the total sample conditioned medium present in the portion of the cell culture conditioned medium not containing cells of the cell population; or (ii) when the ratio of the first percentage to the second percentage deviates from 1:1, calculating the fraction of viable cells by comparing the level of cell death-stable enzyme activity detected in steps (b) and (d) according to the formula: X - cY X + Y + 2 ⁢ ⁢ Y ⁡ ( α - 1 ) wherein c = 1 - f f and f is the fraction of the total sample conditioned medium present in portion of the cell culture conditioned medium not containing cells of the cell population; and wherein a is the ratio of the percentage of the total cells to the percentage of the total conditioned medium present in the sample, wherein the tissue-engineered product comprises a three-dimensional scaffold or matrix and cells are present in the scaffold or matrix.