Xenobiology assumes that un-anticipated life forms and properties would emerge from cell populations with fully integrated novel chemistries. According to this school of thinking the synthesis of chemically modified biomolecules (such as amino acids, nucleobases or enzyme cofactors) employed in classical biomimetic chemistry (which usually examines them outside the cell) should be only the first step on the way to change cellular chemical compositions. Later, the functional features of living systems should be further diversified by acquisition of novel chemistries via artificial evolution of pre-existing cells from the natural world.
We are well aware that this is not a trivial task, as the chemistry of the living cells is notoriously standardized, the genetic code [nearly] universal. Owing to this high degree of standardization and interconnectivity, all changes deep within the living system’s chemistry generally tend to be lethal.
In this context, the important task of Xenobiology is to establish an artificial evolution of cells with altered chemical compositions which are viable and robust to grow and replicate for an unlimited time in genetic isolation from natural species. In the experiment of substitution of components of living cells with non-canonical counterparts unforeseen emergent properties could be predicted.
From this perspective, the design of genetically modified organisms (in the frame of classical genetics) was only the first step of the long way of searching for reliable methodologies to design and deploy artificial biodiversity while preserving the old natural world.
For details see:
Marliere P. The farther, the safer: a manifesto for securely navigating synthetic species away from the old living world. Syst Synth Biol., 2009, 3, 77-84. doi:10.1007/s11693-009-9040-9