Unfortunately you can not render Html, because the panelbaritem text is rendered encoded. It is possible to implement ItemTemplate, which will replace the current rendered html for each item. The decision depends on the number of the requests for that feature.
Currently I can suggest you rebuild the Telerik.Web.Mvc.dll assenbly to render panelbaritem text not encoded.
Here is a code snippet showing how to modify the metod which rendered the item's html:
(In the PanelBarRenderer.cs)