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

Figure 5

T₁ weighted ¹⁹F and ¹H·MRI of samples containing PRE active and MMP-2 cleaved (PRE deactivated) ¹⁹F biosensors at 9.4 Tesla (transverse view). Samples in five separate NMR tubes located in a 30 mm microimaging probe head at 293 K (i) 0.6 mM biosensor (no MMP-2 added), (ii) 0.6 mM biosensor with MMP-2 added after acquisition of images (b) and (c), (iii) 0.6 mM biosensor, diluted to 0.4 mM concentration after images (b) and (c) acquisition, (iv) 0.4 mM cleaved biosensor (cleaved throughout all images), and (v) PBS solution without any Gd(III) or ¹⁹F present. (a) ¹H gradient echo (GE) MRI (of H₂O) showing all samples. (b) T₁ weighted ¹⁹F·GE·MRI showing three samples with 0.6 mM PRE active (not cleaved) biosensor probe. (c) ¹H null point MRI (of H₂O) with inversion recovery time (TI) set to 220 ms leading to vanishing signal in the samples with PRE active biosensor. (d) T₁ weighted ¹⁹F·GE·MRI after MMP-2 catalysed cleavage of biosensor in sample (ii) and dilution of sample (iii) to 0.4 mM. (e) ¹H null point MRI (of H₂O) with TI = 220 ms revealing the concentration change of sample (iii) (false positive). (f) Difference of T₁ weighted ¹⁹F·GE·MRI (d subtracted from b). (g) Absolute value of the difference of ¹H·IR·MRI (e subtracted from c).