Serialize FontFamily in Windows Phone

I'm trying to read/save a xml-file in my windows phone application with the XmlSerializer. Unfortunately I can't read/write it because I'm using the FontFamily in my class:

public class Article
{
    public string name { get; set; }
    private FontFamily _fontitem;
    public FontFamily FontItem
    {
        get
        {
            return _fontitem;
        }
        set
        {
            _fontitem = value;
            RaisePropertyChanged(() => FontItem);
        }
    }
}

I'm using a class named StorageHelper just like here: http://ift.tt/1zUDOKs Instead of the class "Jog" I use my class "Article".

When I try to load/save the xml this error comes up: "fontfamily cannot be serialized because it does not have a paramterless constructor"