Board Thread:Theories and Speculation/@comment-26704954-20150821182356/@comment-24071195-20150821185332

I suppose you could seal the essence of their chakra into someone, but like Jou said, Tailed Beasts are purely chakra which is what made the process possible.

Minato and Kushina were technically sealed into Naruto; manifesting with their full personalities and, in Kushina's case, abilities (chakra chains), but because they were just traces of the dead their chakra ran out and couldn't be used, whereas Tailed Beasts constantly "refill" their chakra while in a jinchuuriki.