DNA Steganograpy

Hi all, while searching for the topic to send messages undetected (not the classic steganography) I have read about DNA steganography and that open source software is available for that. In case someone of you is familiar with this topic, I would like to know the following. How big could the max payload be and regarding organisms, could that do any harm (in the long-range) for, let's say, animals, instead of a plant, if it would be possible to inject messages multiple times? Regards Stefan