The present invention features, inter alia, constructs for the delivery of therapeutic and diagnostic agents to a patient. The constructs can include a nanoparticle, a targeting agent that specifically binds a targeted tissue or cell, a therapeutic moiety, and a hydrogel. The constructs can be used in the treatment and diagnosis of bowel diseases, including inflammatory bowel disease (IBD) and colon cancer. In one embodiment, the therapeutic agent is a nucleic acid that mediates RNA inhibition (RNAi), and the invention is directed to treatments for IBD that combine the positive aspects of such agents {e.g., siRNAs) with the safety of a biodegradable polymeric delivery system to facilitate specific targeting of colonic tissues and cells. As the constructs can be formulated for oral administration, they are well tolerated and offer advantages with regard to patient compliance.
