Synthesis of 4-Amino-1-Hydroxy-Butane-1,1-Diphosphonate (AHBDP) - Stannous Complexes for the Preparation of Ahbdp-Sn(II)-Tc and its Biodistribution in Rats

The new potential tracer of bone imaging, AHBDP-Sn(II)-TcO.3H(2)O was synthesized by reducing the TcO(4) (-) to TcO(2) (+) in the presence of AHBDP and Sn(ll)'s reducing agent. We found that tin rapidly forms a stable complex with AHBDP, giving AHBDP-Sn(II).3H(2)O. In the excess of AHBDP-Sn(ll).3H(2)O, the AHBDP-Sn(II).3H(2)O coordinates with TcO(2) (+) to give AHBDP-Sn(II)-TcO.3H(2)O which could polymerise or oligomerise to give hydrophobic species. The overall process appears as a first-order reaction (K= 0.67 +/- 0.005s(-1)). In rats, the fixation of AHBDP-Sn(II)-(99m)TcO. 3H(2)O on bone is homogeneous and the scintigraphic images have the same quality as those of 1-hydroxymethane-1,1-diphosphonate-Technetium (HMDP-(99m)Tc). The activity in non-target organs was neglible.