If you can build artificial cells, why not build artificial organelles within natural cells? From the New Scientist, a look at the future: "Human cells could have their metabolisms upgraded without altering their genes by inserting tiny plastic packages of enzymes ... [researchers] coated their polymer vesicles in a chemical that encouraged human white blood cells called macrophages to engulf them. The small capsules contained enzymes, just like natural organelles. The enzymes chosen produced fluorescent chemicals, signalling they were working without problems inside their new host. ... Artificial organelles might also be able to treat conditions caused by a deficit of a particular enzyme. For example, someone with lactose intolerance could have their digestive cells given artificial organelles containing lactose-digesting enzymes. In the far future, it might be possible to introduce non-human metabolic functions into human cells. ... We could, in principle, bring in a nanoreactor that [lets] your skin do something like photosynthesis. So if you are hungry, you just lie in the Sun." For "in the far future," read "twenty years from now." I'm sure you can imagine a thousand and one other, more directly beneficial applications of this technology: for example, enzymes to degrade damaging aggregates that accumulate with age.