The invention relates to an oral drug delivery system which delivers biologically active substances to the mucosal tissue of the intestine utilizing novel polymerized liposomes. Novel polymerizable fatty acids having a polymerizable group, a surfactant group, and a functional group, and optionally coupled to ligands which target mucosal tissue in the intestine are disclosed. Novel negatively charged polymerizable lipids which have phosphatidyl inositol (PI), phosphatidyl glycerol (PG) or phosphatidyl serine (PS) groups on a polymerizable backbone are also described.