Detection of targeted perfluorocarbon nanoparticle binding using 19F diffusion weighted MR spectroscopy.

Real-time detection of targeted contrast agent binding is challenging due to background signal from unbound agent. (19)F diffusion weighted MR spectroscopy (DWS) could selectively detect binding of angiogenesis-targeted perfluorocarbon nanoparticles in vivo. Transgenic K14-HPV16 mice with epidermal squamous carcinomas exhibiting up-regulated neovasculature were used, with nontransgenic littermates as controls. Mice were treated with alpha(v)beta(3)-integrin targeted perfluorocarbon nanoparticles. (19)F DWS (b-values from 0 to 16,000 s/mm(2)) was performed on mouse ears in vivo at 11.74 Tesla. Progressive decay of (19)F signal with increased diffusion weighting at low b-values (< 1500 s/mm(2)) was observed in ears of both K14-HPV16 and control mice, demonstrating suppression of background (19)F signal from unbound nanoparticles in the blood. Much of the (19)F signal from ears of K14-HPV16 mice persisted at high b-values, indicating a stationary signal source, reflecting abundant nanoparticle binding to angiogenesis. (19)F signal in controls decayed completely at high b-values (> 1500 s/mm(2)), reflecting a moving signal source due to absence of angiogenesis (no binding sites). Estimated ADCs of nanoparticles in K14-HPV16 and control mice were 33.1 +/- 12.9 microm(2)/s and 19563 +/- 5858 microm(2)/s (p < 0.01). In vivo (19)F DWS can be used for specific detection of bound perfluorocarbon nanoparticles by selectively suppressing background (19)F signal from nanoparticles flowing in blood.