Before answering this question, we have to think in new material, graphene. Although it seems contradictory, this material, practically transparent is able to ‘ ‘ steal the light ‘ ‘ from other molecules like the cyaninas. In a recent study it has been shown that, cell can absorb and split the molecules attached in graphene and them, emit light! So, yes! in certain conditions our cells can emit light in the visible region!
Will it have real applications, or will it be like a simple curiosity, what do you think?
https://www.sciencedirect.com/science/article/pii/S0143720819323186