“it is a cell of a living animal.”
what is?
As I mentioned IF it is from a living animal, (it doesnt have to be they can (and have) used embryonic cells and of course they cfan shecht an animal and use its cells) then that cell might not be batul as arguably it is a davar hamamid. Adavar hammaid is an ingredient that is necessary for the finished product. The classic example is rennet without which you wouldnt have cheese.
On the other hand maybe a microscopic cell is less of a davar hammamid since it isnt even viible to the eye.
Though perhaps it is worse since it literally leads to every other cell being produced.
If it isnt a davar hamamid youd have less of a problem. while of course chatzi shiur is assur. a cell might be batul