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. Author manuscript; available in PMC: 2021 Apr 15.
Published in final edited form as: Inorg Chem. 2020 May 5;59(10):6648–6678. doi: 10.1021/acs.inorgchem.0c00510

Table 9.

Comparison of biochemically mediated r1 change achieved with representative Gd and transition metal complexes studied as biochemically responsive contrast agents.

r1 change triggered by: mechanism of r1 change “off” r1/ “on” r1 (mM−1s−1), magnitude r1 change.
0.47T 1.4T >3.0T
EgadMe197 β-galactosidase q increase N/Da N/Da 0.9/ 2.7b, 3-fold
Gd-MPO H2O2/myeloperoxidase τR increase by oligomerization 4.3/10.5, 2.4-fold207 N/D 4.9/4.8c, no change110
Gd-LZn252 Zn2+ binding and subsequent HSA association τR increase from Zn2+ triggered albumin binding 5.8/18, 3.1-fold N/D 6.0/6.8d, ~10%
Gd-4AmP203–204 pH change Prototropic exchange, second sphere N/D N/D 6.0 (pH 6)/ 4.0 (pH 4), ~50%, or ~5% per 0.1 pH unitd
Mn-TPPS492 O2 Oxidation from Mn2+ to Mn3+ 10/12, ~20% N/D N/D
Mn-TPPS492 O2, in presence of β-cyclodextrin Oxidation from Mn2+ to Mn3+ 23/58, ~2.5 fold N/D N/D
Mn-HBET213 Redox (H2O2, L-Cys) Mn2+/Mn3+ interchange N/D 1.1/2.8, 2.5-fold 1.1/3.9d, 3.5-fold
Mn-HBET-NO2213 Redox Mn2+/Mn3+ interchange N/D 0.50/2.3, 5.8-fold 0.7/3.1d, 4.4-fold
Mn-CyHBET213 Redox Mn2+/Mn3+ interchange N/D 0.40/3.3, 8.3-fold
Mn-CyHBET-NO2213 Redox Mn2+/Mn3+ interchange N/D 0.50/2.3, 5.6-fold
Mn-JED217 Redox (H2O2/peroxidase, L-Cys) Mn2+/Mn3+ interchange N/D 0.5/3.3, 6.6-fold
0.9/8.0, 8.9-fold		 0.9/4.3d, 4.8-fold
1.1/ 3.6b, 4.6-fold
0.5/2.5d, 5.0-fold
0.5/ 1.9b, 3.8-fold
Mn-HPTP1 H2O2 Dimerization, τR increase N/D N/D 4.4–3.6e, ~ −20%
Fe-PyC3A110 H2O2, L-cys Fe2+/Fe3+ interchange N/D 0.18/1.8, 10-fold 0.18/2.4d, 13-fold
0.15/2.2b, 15-fold
a

r1 change from q modulation is field independent.

b

11.7T

c

4.7T

d

9.4T

e

3.0T