Use Left-handed sugar & protien molecules (Score 1)

This explains a little bit. You can build into the design an inabillity to interact with our biology by simply using the "mirror-image" of our base molecular structure. Feynman was one of the first to recognize the potential for a parallel biology, and that it was just by chance that earth biology evolved from a "right-handed" structure. If we limit these expariments to "left-handed" structures, we significantly reduce the threat of unintentional hazards.