Smart MR contrast agents are chelated paramagnetic molecules, whose relaxivity changes as a function of their chemical environment (e.g. changes in pH, calcium or neurotransmitter concentration). The multifunctional chelating agent DO3A-EA (-ethylamine) has been designed and synthesized as a valuable multifunctional precursor for smart MR contrast agents based on Gd-chelates. DO3A-EA was conjugated with diverse bioorganic molecules: 1) Gdpreloaded precursor Gd-DO3A-E-NCS with a highly reactive electrophile group for interaction with biological molecules or further synthesis. 2) Biotinconjugated Gd-DO3A-E-Biotin for targeted imaging in an antibody-avidin system. 3) Fluorescence probe DO3A-E-FITC to track cell internalization and binding.