"Could we really be made of Swiss cheese?" is paper that explains xenobiology. It's really great introduction to xenobiology. I recommend to read it. PDF
Xenobiology studies life with alternate way to get energy.
Xenobiology can provide potential medical and biosafety applications, as well as challenge the foundations of biological engineering. This paper reviews the philosophical aspect of xenobiology, focusing on the possible multiple realizability of life.
Synthetic philosophical theories aim to design systems with natural functions, rather than biological functions, to test chemistry and understand life.