Abstract
Gallium-68 has been the subject of increasing interest for its potential in the production of radio-tracers for diagnosis of diseases. In this work we report the complexation of (68)Ga by the amino acid based tripodal chelate H(3)Dpaa, and two bifunctional derivatives, H(3)Dpaa. dab and H(4)Dpaa.ga, under a range of conditions with particular emphasis on the rapid complexation of (68)Ga at pH 7.4. 100 μM H(3)Dpaa achieved a radiochemical yield of 95% at pH 7.4 in 5 minutes at 37 °C.
The bifunctional derivatives H(4)Dpaa.ga and H(3)Dpaa. dab achieved 94% and 84% radiochemical yields, respectively, under the same conditions. The resulting Ga(III) complexes show thermodynamic stabilities of log K(GaDpaa) = 18.53, log K(GaDpaa.dab) = 22.08, log K(GaDpaa.ga) = 18.36.
Unfortunately, the resulting radiolabelled species do not present sufficient serum stability for in vivo application. Herein we show a flexible synthesis for bifunctional chelators based on amino acids that rapidly complex (68)Ga under physiological conditions.