Gold Nanoparticles Functionalized with Gadolinium Chelates as High Relaxivity MRI Contrast Agents.

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1 Supporting information for Gold Nanoparticles Functionalized with Gadolinium Chelates as High Relaxivity MRI Contrast Agents. Loïck Moriggi, Caroline Cannizzo, Eddy Dumas, Cédric R. Mayer*, Alexey Ulianov and Lothar Helm* Scheme 1. Synthetic route for Dt (5). Table S1. Quantities of HAuCl 4 and Dt used to synthesize two DtNP solutions. HAuCl 4 + Dt NaBH 4 0 C DtNP in CH 3OH in H 2O/ acetic acid (1) 15.5 µmol µmol DtNP(1) (2) 46.5 µmol µmol DtNP(2) Gadolinium, yttrium and gold concentrations in solution were determined by ICP-MS analysis using an ELAN 6100 DRC mass spectrometer (Perkin Elmer, Norfolk, Canada) interfaced to an Apex sample introduction system (Epond SA, Vevey, Switzerland) in the Institut de Minéralogie et Géochimie at Université de Lausanne (Lausanne ; Switzerland). Two standards with known concentrations of Y 3+, Gd 3+ and Au 3+ were prepared from titrated solutions. All blank, standard and sample solutions were acidified by adding 0.2 HNO 3 and doped with 0.38 ppm 103 Rh for internal standardization. S1

2 Table S2. Effective magnetic moments µ eff calculated from the 1 H NMR shift x of the t-butyl alcohol resonance due to Gd-DtNP (measured at 18.8 T and K) and [Gd 3+ ] obtained by ICP-MS for the two batches Gd- DtNP(1) and Gd-DtNP(2) and diluted solutions of Gd-DtNP(2), Gd-DtNP(2)-2, Gd-DtNP(2)-3 and Gd-DtNP(2)-4. [Gd 3+ ] [µm] * µ eff ** Gd-DtNP(1) (0.8) 8.12 Gd-DtNP(2) (0.5) 8.43 Gd-DtNP(2) (0.3) 7.81 Gd-DtNP(2) (0.2) 8.80 Gd-DtNP(2) (0.2) 7.64 * Gadolinium(III) concentration measured by ICP-MS. ** Effective magnetic moment measured with the Evans method. 1,2 Table S3. Parameters from fits of {Ru[bpy-DTTA 2(H 2O) 4] 3} 4- and Gd-DtNP(1) 1 H NMRD profiles using the modified Florence approach. {Ru II [Gd 2bpy- DTTA 2(H 2O) 4] 3} 4- Gd-DtNP(1) k 298 ex 10 6 s τ R ps τ v ps t s s s S2

3 Figures Figure S1. TEM images of Gd-DtNP(1) and Gd-DtNP(2) solution carried out onto a carbon-coated copper grid (Transmission electron microscope (TEM) JEOL 2010 UHR in the Interdisciplinary Centre for Electron Microscopy (CIME) at EPFL Lausanne, Switzerland). (a) (b) Figure S2. STEM with EDX analysis. (a) STEM images, with the pathway (line 11) followed for the EDX analysis shown in (b). The lower point of the pathway (line 11) is the starting point 0 in (b). S3

4 Figure S3. Diameter size distributions obtained with transmission electron microscope (TEM) images treatment and dynamic light scattering (DLS). Figure S4. Space-filling MM3 optimized model of Au 201[Y-Dt(H 2O) 2] 56. S4

5 Figure S5. 1 H nuclear magnetic relaxation dispersion (NMRD) profiles, recorded at 25 C of Gd- DtNP(1), Gd-DtNP(2), Ru-based metallostar {Ru[Gd 2bpy-DTTA 2(H 2O) 4] 3} 4- and the bimetallic complex [Gd 2bpy-DTTA 2(H 2O) 4] 2-. The 1/T 1 NMRD profiles of Gd-DtNP(1) and Gd-DtNP(2) were obtained at 25.0 C on a Stelar Spinmaster fast field cycling NMR relaxometer ( T; proton Larmor frequencies MHz) equipped with a VTC90 temperature control unit, on Bruker Minispecs (0.71 T (30 MHz), 0.94 T (40 MHz), and 1.41 T (60 MHz)), on a Bruker Avance-200 console connected to 2.35 T (100 MHz), and 4.7 T (200 MHz) cryomagnets and on a Bruker DRX-400 (9.4 T, 400 MHz). The diamagnetic correction to the 1 H longitudinal relaxation rates were 0.37 s -1 (25.0 C) r 1 /mm -1 s ν 1 ( 1 H) /MHz Figure S6. 1 H nuclear magnetic relaxation dispersion (NMRD) profiles of Gd-DtNP(1) recorded at 25 C ( ) and 37 C ( ). The diamagnetic corrections to the 1 H longitudinal relaxation rates were 0.37 s -1 (25 C), and 0.33 s -1 (37 C). S5

6 Supplementary discussion The DTTA chelating unit used to derivatize the gold nanoparticles is known to form complexes with Gd 3+ accomodating two water molecules in the first coordination sphere. It has been shown that the stability of these complexes is comparable to Gd-DTPA-BMA. 3 Due to the problem of nephrogenic systemic fibrosis (NSF) 4 encountered with contrast agents with relatively low stability the nanoparticles synthesized will not be used in clinics but are probably sufficiently stable to be used with animals. The dense packing of Gd-ions on the surface of Gd-DtNP suspects to have interaction between them leading to an increase in electron spin relaxation. 5 The parameters describing electron spin relaxation (Table S2) do not support this hypothesis, but further experimental investigation is needed to exclude such interaction which would limit the 1 H relaxivity. Gold nanoparticles derivatized with gadolinium chelating ligands have been synthesized by Tillement 6,7 and Kim 8. Both used ligands which are able to bind several Gd 3+ ions. Relaxivities (per Gd 3+ ion) given in ref. [7] at the high field of 7 T (corresponding to ν( 1 H) = 300 MHz) are 2.5 mm -1 s -1 to 4.1 mm -1 s -1 which is comparable to contrast agents based on small complexes used in clinics. Kim 8 gives a relaxivity of 10.5 mm -1 s -1 at 1.5 T (64 MHz). In this paper it is observed that more than 10 4 Gd 3+ ions are bound to nanoparticles of Au@GdL with the mean size of 5 7 nm. It seems to be evident that the means size given corresponds to the gold core and the overall size of the NPs is much larger. The high relaxivity of our Gd-DtNP (at 25 C: 60 mm -1 s -1 at 0.7 T/30 MHz, 50 mm -1 s -1 at 1.4 T/60 MHz, and 14 mm -1 s -1 at 4.7 T/200 MHz) is due to the rigidity of the particles as well as the number of two water molecules coordinated per Gd 3+ ion. As can be seen from Figure S6 relaxivity at 37 C is about the same as at 25 C indicating that slow water exchange is limiting relaxivity. The rotational correlation time calculated from the fit of the NMRD profile (τ R = 1.2 ns, Table S2) seems to be rather short for a particle with a radius of 2.4 nm. The radius calculated using the Debye-Stokes-Einstein relation and the measured τ R is about 1.1 nm. One has to keep in mind that in solution a distribution of sizes is observed (Figure 1). Again further experimental studies are necessary to clarify this point. References used in the Supporting Information (1) Evans, D. F. J. Chem. Soc. 1959, (2) Evans, D. F.; Fazakerley, G. V.; Phillips, R. F. J. Chem. Soc. A 1971, (3) Moriggi, L.; Cannizzo, C.; Prestinari, C.; Berrière, F.; Helm, L. Inorg. Chem. 2008, 47, (4) Agarwal, R.; Brunelli, S. M.; Williams, K.; Mitchell, M. D.; Feldman, H. I.; Umscheid, C. A. Nephrol. Dial. Transplant. 2009, 24, (5) Nicolle, G. M.; Helm, L.; Merbach, A. Magn. Reson. Chem. 2003, 41, (6) Debouttiere, P.-J.; Roux, S.; Vocanson, F.; Billotey, C.; Beuf, O.; Favre-Reguillon, A.; Lin, Y.; Pellet-Rostaing, S.; Lamartine, R.; Perriat, P.; Tillement, O. Adv. Funct. Mater. 2006, 16, (7) Alric, C.; Taleb, J.; Le Duc, G.; Mandon, C.; Billotey, C.; Le Meur-Herland, A.; Brochard, T.; Vocanson, F.; Janier, M.; Perriat, P.; Roux, S.; Tillement, O. J. Am. Chem. Soc. 2008, 130, (8) Park, J.-A.; Reddy, P. A. N.; Kim, H.-K.; Kim, I.-S.; Kim, G.-C.; Chang, Y.; Kim, T.-J. Bioorg. Med. Chem. Lett. 2008, 18, S6