From my quick skip of relevant literature (there's a butt load of research in antibacterial hydrogels), we really aren't in any position to answer that question yet. The mechanism described in the press release is actually speculative.

Many of the papers raise that mechanism as a possibility, but they'll also note that there are many human cells that have a cell membrane at least as electronegative as bacteria, and that they witness antibacterial effects against relatively neutrally charged bacteria membranes as well. One example can be found here [1]. Try flipping through the mechanism and cytotoxicity (how dangerous it is to human cells) sections.

Basically, this is all exciting new research, but there really are no hard answers yet.

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2650250/