Verwilst, P. Eliseeva, S. V. Vander Elst, L. Burtea, C. Laurent, S. Petoud, S. Muller, R. N. Parac-Vogt, T. N. De Borggraeve, W. M.
Inorganic Chemistry (2012) 51 (11) 6405-6411 - doi : 10.1021/ic300717m
Gd-III-containing metallostar contrast agents are gaining increased attention, because their architecture allows for a slower tumbling rate, which, in turn, results in larger relaxivities. So far, these metallostars find possible applications as blood pool contrast agents. In this work, the first example of a tissue-selective metallostar contrast agent is described. This RGD-peptide decorated Ru-II(Gd-III)(3) metallostar is synthesized as an alpha(v)beta(3)-integrin specific contrast agent, with possible applications in the detection of atherosclerotic plaques and tumor angiogenesis. The contrast agent showed a relaxivity of 9.65 s(-1) mM(-1), which represents an increase of 170%, compared to a low-molecular-weight analogue, because of a decreased tumbling rate (tau(R) = 470 ps). The presence of the MLCT band (absorption 375-500 nm, emission 525-850 nm) of the central Ru-II(Ph-Phen)(3)-based complex grants the metallostar attractive luminescent properties. The (MLCT)-M-3 emission is characterized by a quantum yield of 4.69% and a lifetime of 804 ns, which makes it an interesting candidate for time-gated luminescence imaging. The potential application as a selective MRI contrast agent for alpha(v)beta(3)-integrin expressing tissues is shown by an in vitro relaxometric analysis, as well as an in vitro T-1-weighted MR image.