PurposeTo compare the levels of gadolinium in the blood, cerebrum, cerebellum, liver, femur, kidneys, and skin after multiple exposure of rats to the macrocyclic gadolinium‐based contrast agents (GBCAs) gadoterate, gadobutrol, and gadoteridol.Materials and MethodsFifty male Wistar Han rats were randomized to three exposure groups (n = 15 per group) and one control group (n = 5). Animals in the exposure groups received a total of 20 GBCA administrations (four administrations per week for 5 consecutive weeks) at a dose of 0.6 mmol/kg bodyweight. After a 28‐day recovery period animals were sacrificed and the blood and tissues harvested for determination of gadolinium (Gd) levels. Gd determination was performed by inductively coupled plasma mass spectrometry (ICP‐MS).ResultsAfter 28 days' recovery no Gd was found in the blood, liver, or skin of any animal in any group. Significantly lower levels of Gd were noted with gadoteridol compared to gadoterate and gadobutrol in the cerebellum (0.150 ± 0.022 vs. 0.292 ± 0.057 and 0.287 ± 0.056 nmol/g, respectively; P < 0.001), cerebrum (0.116 ± 0.036 vs. 0.250 ± 0.032 and 0.263 ± 0.045 nmol/g, respectively; P < 0.001), and kidneys (25 ± 13 vs. 139 ± 88 [P < 0.01] and 204 ± 109 [P < 0.001], respectively). Higher levels of Gd were noted in the femur (7.48 ± 1.37 vs. 5.69 ± 1.75 and 8.60 ± 2.04 nmol/g, respectively) with significantly less Gd determined for gadoterate than for gadobutrol (P < 0.001) and gadoteridol (P < 0.05).ConclusionDifferences exist between macrocyclic agents in terms of their propensity to accumulate in tissues. The observed differences in Gd concentration point to differences in GBCA washout rates in this setting and in this experimental model, with gadoteridol being the GBCA that is most efficiently removed from both cerebral and renal tissues. Level of Evidence: 2 Technical Efficacy: Stage 5J. Magn. Reson. Imaging 2018;47:746–752.

Dlvlnyisulphone-activated agarose to which mercaptoethanol IS coupled showed very setectlve group adsorption of human serum protems, m particular the ~mmunogIobul~ns The adsorptxon Increases markedly m the presence of high concentrations of neutral water-structure formmg salts and IS dlstmct from adsorptions based on hydrophobic mteractlon A characterlstlc feature of this new type of adsorbent 1s the structure of the groups attached to the polymer, @, I e , R-S-CH,-CH,-SO,-CH,-cH,-O-Q, where R IS a small ahphatlc residue Our results mdlcate that the thloether sulphur and the adJacent sulphone group act cooperatlvely and are apparently necessary to mamtam the dlstmct behavlour of such dbsorbents

We report the synthesis of novel chelates of Gd and (68)Ga with DPTA, DOTA, HP-DOA3, as well as with AAZTA, a novel chelating agent developed by our research group. These chelating agents were appropriately conjugated, prior to metal complexation, with DB58, an RGD peptidomimetic, conformationally constrained on an azabicycloalkane scaffold and endowed with high affinity for integrin α(ν)β(3) . Because α(ν)β(3) is involved in neo-angiogenesis in solid tumors and is also directly expressed in cancer cells (e.g. glioblastomas, melanomas) and ovarian, breast, and prostate cancers, these constructs could prove useful as molecular imaging probes in cancer diagnosis by MRI or PET techniques. Molecular modeling, integrin binding assays, and relaxivity assessments allowed the selection of compounds suitable for multiple expression on dendrimeric or nanoparticulate structures. These results also led us to an exploratory investigation of (68)Ga complexation for the promising (68)Ga-PET technique; the AAZTA complex 15((68)Ga) exhibited uptake in a xenograft model of glioblastoma, suggesting potentially useful developments with new probes with improved affinity.

Objectives: The purpose of this study was to compare Gd levels in rat tissues after cumulative exposure to four commercially available macrocyclic gadolinium-based contrast agents (GBCAs). Methods: Sixty-five male Sprague-Dawley rats were randomized to four exposure groups (n = 15 per group) and one control group (n = 5). Animals in each exposure group received 20 GBCA administrations (four per week of ProHance®, Dotarem®, Clariscan™, or Gadovist® for 5 consecutive weeks) at a dose of 0.6 mmol/kg bodyweight. After 28-days' recovery, animals were sacrificed and tissues harvested for Gd determination by inductively coupled plasma-mass spectroscopy (ICP-MS). Histologic assessment of the kidney tissue was performed for all animals.

α(V)β(3) Integrins are a widely recognized target for in vivo molecular imaging of pathological conditions such as inflammation, cancer and rheumatoid arthritis. We have evaluated the sensitivity of a new, near-infrared fluorescence (NIRF), RGD cyclic probe (DA364) in noninvasive detection of α(V) β(3) integrin-overexpressing tumors. DA364's binding affinity for α(V)β(3) integrin was first evaluated in vitro. Human α(V)β(3) integrin-positive, U-87 MG glioblastoma cells were then xenografted in nude mice, and DA364 was injected intravenously (i.v.) to evaluate its in vivo distribution, specificity and sensitivity in comparison with a commercially available probe. DA364 bound α(V)β(3) integrin on U-87 MG cells with high affinity and specificity, both in vitro and in vivo. This binding specificity was corroborated by the strong inhibition of its tumor uptake induced by nonfluorescent, cyclic-RGD peptides. Ex vivo analysis showed that DA364 accumulated at the tumor site, whereas very low levels were detected in liver and spleen. In conclusion, DA364 allows sensitive and specific detection of transplantable glioblastoma by NIRF imaging, and is thus a promising candidate for the elaboration of imaging and therapeutic probes for α(V)β(3) integrin-overexpressing tumors.