Gadolinium Complex of (125)I/(127)I-RGD-DOTA Conjugate as a Tumor-Targeting SPECT/MR Bimodal Imaging Probe.

The work describes the synthesis and in vivo application of [Gd(L)(H2O)]·xH2O, where L is a ((125)I/(127)I-RGD)- DOTA conjugate, as a tumor-targeting SPECT/MR bimodal imaging probe. Here, ((125)I/(127)I-RGD)-DOTA signifies a "cocktail mixture" of radioisotopic (1a, L = (125)I-RGD-DOTA) and natural (1b, L = (127)I-RGD-DOTA) Gd complexes. The two complexes are chemically equivalent as revealed by HPLC, and their cocktail mixture exhibits the integrin-specific tumor enhancement, demonstrating that they constitute essentially a single bimodal imaging probe. Employment of a cocktail mixture thus proves to be a sole and practical approach to overcome the sensitivity difference problem between MRI and SPECT.