They're artificial organs so, pretty much biological augmentation. You can also grow fully formed astartes from artificial wombs but THATS HERETEK. Chaos Mahreens kinda had a project like that going by creating artificial wombs out of living women, creating the daemonculaba.
To my knowledge you can't actually grow a marine from scratch. The daemonculaba were just a way to speed up the creation process by adding a young boy, geneseed and warp magic together inside a damonically possessed woman's womb to make an insta-abomination marine.
So, uh, anyway, in the matter of 40k plot devices, what the fuck is Cypher about? Is he so much of a Dark Angel that he out Dark Angeled the Dark Angels so hard he became a fallen/walking alpha legion analogy who's apparently somehow not a pawn of Tzeench?
Cypher is a mystery. It's kind of the point of him.
His name is actually a title from the days of the Great Crusade. The Lord Cypher was a position in the Dark Angels entrusted with the various dark secrets of Caliban and the Legion.
As for his current allegiance and goals, no one knows. He bears a broken sword, which some think may be a relic of the Lion, which he may or may not be hoping to use to heal the Emperor or kill him, he may or may not be a pawn of chaos, so on and so forth.
All we really know is he spreads discord behind him like a boat leaves a wake and that he knows the truth of what happened to the Dark Angels in the waning of the Horus Heresy.