I will determine the concentration of carboxylesterase enzyme in mice liver using Enzyme-linked Immunosorbent Assay (ELISA). I will run the experiment in four steps (each of them is 60 days). If I want to keep the liver samples to analysis together, how long they can survive without no changes in both of the stucture and function of cell, protein, etc,

Would you give some suggestion?

Thank you very much