Polymer based gene delivery systems have been widely studied for their safety and simple preparation compared with viral gene carriers [1].However,in most cases the polymer based gene carriers could only achieve transient gene transfection due to the different transfection mechanism fiom viral gene carriers.For cancer gene therapy or tissue engineering,stable or long-term gene transfection is needed to achieve prolonged therapeutic effects [2].Hydrogels have been utilized in controlled drug releasein vivo and sustained drug delivery has been achieved for cancer therapy [3].