Synthesis of dansyl bisphosphonic acid (3) and attachment to the oxidized surface of Ti6Al4V foil. A. 2-(2-mercaptoethylamino) ethylidene-1,1-bisphosphonic acid (1): (i) water, 110°C, 6 hr. (ii) Me3P. B. Dansyl bisphosphonic acid (3): (i) dansyl chloride, rt 2 hr. (ii) bromoacetic acid, DCC, EtOAc. (iii) 2-(2-mercaptoethylamino)ethylidene-1,1-bisphosphonic acid (1), 50% Me2NCHO/50% water. C. Attachment to Ti6Al4V foil.