Accelerated ¹⁹F·MRI Detection of Matrix Metalloproteinase-2/-9 through Responsive Deactivation of Paramagnetic Relaxation Enhancement

Figure 4

Transverse ¹⁹F·MRI at 9.4 Tesla and 293 K of three separate 5 mm NMR tubes (located within a 30 mm microimaging probe head), each containing 600 μL of 1.2 mM solution of the respective ¹⁹F samples in 9 : 1 v/v H₂O/acetonitrile solution, were used to demonstrate the effect of negative T₁ contrast for molecular imaging. (a) Sketch of the sample (transverse view): (i) 1.2 mM biosensor without MMP. (ii) 1.2 mM biosensor with MMP-2 added at t = 0 s. (iii) ¹⁹F control containing 1.2 mM of tetrafluoroacetate (TFA) and 1.2 mM of Gd-DOTA. Samples were kept at 293 K throughout the reaction. (b) T₁ weighted ¹⁹F·UTE·MRI at various times with MMP-2 added to sample (ii) at t = 0 demonstrating negative contrast with progressing time. (c) T₂¹⁹F weighted spin echo (SE) MRI demonstrating the effect of positive contrast. Recording time t (rounded to the nearest full hour) indicates the beginning of the UTE MRI acquisition (6 min recording time per image) that is followed after completion by the SE MRI (75 min recording per image).