A therapeutic agent delivery system formed of a specific type of poly(ester amide) (PEA), a therapeutic agent, and a water miscible solvent is described herein. A method of delivering the therapeutic agent delivery system by delivering the therapeutic agent delivery system formed of a PEA polymer, a therapeutic agent, and a water miscible solvent to a physiological environment and separating the phase of the therapeutic agent delivery system to form a membrane from the polymer to contain the therapeutic agent within the physiological environment is also described. Additionally disclosed is a kit including a syringe and a therapeutic agent delivery system within the syringe.