Gadolinium Complex of 125I/127I-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)]center dot xH(2)O, where L is a (I-125/I-127-RGD)- DOTA conjugate, as a tumor-targeting SPECT/MR bimodal imaging probe. Here, (I-125/I-127-RGD)-DOTA signifies a cocktail mixture of radioisotopic (1a, L = I-125-RGD-DOTA) and natural (1b, L = I-127-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.