There was an article in the November 2008 shooting times that discusses some much older testing that indicates that silicone would probably work. Here's the link:
http://www.shootingtimes.com/ammunit...811/index.html
Basically it talks about some experimentation the Dallas crime lab did back in the 70's. They found that filling hollow points with paraffin (which would turn to liquid under pressure) would make them expand more reliably.