Titanium is pretty much inert to the human body, that's why they use it for implants, rods, screws, etc.,etc. I have three titanium bolts in my spine, felt real good when they were fresh.
There was an episode of NCIS called Under Covers where an assassin had one of those put in her eye, except it was really a computer chip in the shape of a heart that held all of her assassin secrets and stuff. Haha.