Provided herein are polymers comprising Metformin residues ("PolyMet") as useful therapeutic agents, delivery vehicles and transfection agents for nucleotides. Also provided herein are methods for the treatment of a disease or an unwanted condition in a subject, wherein the methods comprise administering PolyMet as a therapeutic agent to combat the disease or condition. Also provided herein are methods for the treatment of a disease or an unwanted condition in a subject, wherein the methods comprise administering a therapeutic agent in a delivery vehicle that comprises PolyMet. Further provided herein are methods for making PolyMet.