Reaching beyond the surface in plasma treatments

Cold atmospheric pressure plasmas have been shown to possess bactericidal potential. Many research groups are looking into developing biomedical applications for plasma; however some big questions still remain. There are several main hurdles that need to be jumped before plasma has a chance to break through into the medical treatments market, one of these is penetration. Can plasma penetrate beyond the surface and reach cells beyond those on the surface? Can we make plasma treatments to penetrate, for example, through skin?