Iopamidol Abatement from Waters: A Rigorous Approach to Determine Physicochemical Parameters Needed to Scale Up from Batch to Continuous Operation.

The abatement of iopamidol (IPM), an X-ray iodinated contrast agent, in aqueous solution using powdered activated carbon (PAC) as a sorbent was investigated in the present work. The material was characterized by various analytical techniques such as thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, dynamic light scattering, and zeta potential measurements. Both thermodynamic and kinetic experiments were conducted in a batch apparatus, and the effects of the initial concentration of IPM, the temperature, and the adsorbent bulk density on the adsorption kinetics were investigated. The adsorption isotherms were interpreted well using the Langmuir model. Moreover, it was demonstrated that IPM adsorption on PAC is spontaneous and exothermic (ΔH0 = -27 kJ mol-1). The adsorption kinetic data were described using a dynamic intraparticle model for fluid-solid adsorption kinetics (ADIM) allowing determination of a surface activation energy Es = 6 ± 1 kJ mol-1. Comparing the experimental results and the model predictions, a good model fit was obtained.

Electrochemical Iodination through the In Situ Generation of Iodinating Agents: A Promising Green Approach.

The synthesis of iodinated compounds using cheap, simple, and green strategies is of fundamental importance. Iodination reactions are mainly used to synthesize useful intermediates, especially in the pharmaceutical field, where they are employed for the production of contrast media or of iodinated active pharmaceutical ingredients. Traditional synthetic methods suffer from the use of erosive, toxic, or hazardous reactants. Approaches which involve the use of molecular iodine as an iodinating agent require the addition of an oxidizing agent, which is often difficult to handle. Electrochemistry can offer a valid and green alternative by avoiding the addition of such oxidizing agents, transforming the iodine source in the active species through the use of electrons as the main reactants. Herein, we report the electrochemical iodination with the generation of iodinating species in situ in water by using iodides as the source of iodine atoms. First of all, the electrochemical behavior of iodide and iodine in water on carbonaceous anodes was studied and, after selecting the suitable potential, in situ electrochemical iodination was successfully applied to 5-hydroxyisophthalic acid and 5-sulfosalicylic acid, comparing the iodinating power of I2 and iodonium species.

AAZTA: An Ideal Chelating Agent for the Development of 44 Sc PET Imaging Agents.

Unprecedented fast and efficient complexation of ScIII was demonstrated with the chelating agent AAZTA (AAZTA=1,4-bis(carboxymethyl)-6-[bis(carboxymethyl)]amino-6-methylperhydro-1,4-diazepine) under mild experimental conditions. The robustness of the 44 Sc(AAZTA)- chelate and conjugated biomolecules thereof is further shown by in vivo PET imaging in healthy and tumor mice models. The new results pave the way towards development of efficient Sc-based radiopharmaceuticals using the AAZTA chelator.

Myelography Iodinated Contrast Media. 2. Conformational Versatility of Iopamidol in the Solid State.

The phenomenon of polymorphism is of great relevance in pharmaceutics, since different polymorphs have different physicochemical properties, e.g., solubility, hence, bioavailability. Coupling diffractometric and spectroscopic experiments with thermodynamic analysis and computational work opens to a methodological approach which provides information on both structure and dynamics in the solid as well as in solution. The present work reports on the conformational changes in crystalline iopamidol, which is characterized by atropisomerism, a phenomenon that influences both the solution properties and the distinct crystal phases. The conformation of iopamidol is discussed for three different crystal phases. In the anhydrous and monohydrate crystal forms, iopamidol molecules display a syn conformation of the long branches stemming out from the triiodobenzene ring, while in the pentahydrate phase the anti conformation is found. IR and Raman spectroscopic studies carried out on the three crystal forms, jointly with quantum chemical computations, revealed that the markedly different spectral features can be specifically attributed to the different molecular conformations. Our results on the conformational versatility of iopamidol in different crystalline phases, linking structural and spectroscopic evidence for the solution state and the solid forms, provide a definite protocol for grasping the signals that can be taken as conformational markers. This is the first step for understanding the crystallization mechanism occurring in supersaturated solution of iopamidol molecules.

Myelography iodinated contrast media. I. Unraveling the atropisomerism properties in solution.

The present work reports a thorough conformational analysis of iodinated contrast media: iomeprol, iopamidol (the world's most utilized contrast agent), and iopromide. Its main aim is the understanding of the complex structural features of these atropisomeric molecules, characterized by the presence of many conformers with hindered rotations, and of the role of atropisomerism in the physicochemical properties of their aqueous solutions. The problem was tackled by using an extensive analysis of (13)C NMR data on the solutions of whole molecules and of simple precursors in addition to FT-IR investigation and molecular simulations. This analysis demonstrated that out of the many possible atropisomers, only a few are significantly populated, and their relative population is provided. The conformational analysis also indicated that the presence of a sterically hindered amidic bond, allowing a significant population of cis forms (E in iopromide and exo in iomeprol), may be the basis for an increased thermodynamic solubility of concentrated solutions of iomeprol.

The role of equilibrium and kinetic properties in the dissociation of Gd[DTPA-bis(methylamide)] (Omniscan) at near to physiological conditions.

[Gd(DTPA-BMA)] is the principal constituent of Omniscan, a magnetic resonance imaging (MRI) contrast agent. In body fluids, endogenous ions (Zn(2+), Cu(2+), and Ca(2+)) may displace the Gd(3+). To assess the extent of displacement at equilibrium, the stability constants of DTPA-BMA(3-) complexes of Gd(3+), Ca(2+), Zn(2+), and Cu(2+) have been determined at 37 °C in 0.15 M NaCl. The order of these stability constants is as follows: GdL≈CuL>ZnL≫CaL. Applying a simplified blood plasma model, the extent of dissociation of Omniscan (0.35 mM [Gd(DTPA-BMA)]) was found to be 17% by the formation of Gd(PO4), [Zn(DTPA-BMA)](-) (2.4%), [Cu(DTPA-BMA)](-) (0.2%), and [Ca(DTPA-BMA)](-) (17.7%). By capillary electrophoresis, the formation of [Ca(DTPA-BMA)](-) has been detected in human serum spiked with [Gd(DTPA-BMA)] (2.0 mM) at pH 7.4. Transmetallation reactions between [Gd(DTPA-BMA)] and Cu(2+) at 37 °C in the presence of citrate, phosphate, and bicarbonate ions occur by dissociation of the complex assisted by the endogenous ligands. At physiological concentrations of citrate, phosphate, and bicarbonate ions, the half-life of dissociation of [Gd(DTPA-BMA)] was calculated to be 9.3 h at pH 7.4. Considering the rates of distribution and dissociation of [Gd(DTPA-BMA)] in the extracellular space of the body, an open two-compartment model has been developed, which allows prediction of the extent of dissociation of the Gd(III) complex in body fluids depending on the rate of elimination of the contrast agent.

A general MRI-CEST ratiometric approach for pH imaging: demonstration of in vivo pH mapping with iobitridol.

Chemical exchange saturation transfer (CEST) is a novel contrast mechanism for magnetic resonance imaging (MRI). CEST MRI selectively saturates exchangeable protons that are transferred to MRI-detectable bulk water signal. MRI-CEST (pH)-responsive agents are probes able to map pH in the microenvironment in which they distribute. To minimize the confounding effects of contrast agent concentration, researchers have developed ratiometric CEST imaging, which investigates contrast agents containing multiple magnetically non-equivalent proton groups, whose prototropic exchange have different pH responses. However, conventional ratiometric CEST MRI imposes stringent requirements on the selection of CEST contrasts agents. In this study, a novel ratiometric pH MRI method based on the analysis of CEST effects under different radio frequency irradiation power levels was developed. The proposed method has been demonstrated using iobitridol, an X-ray contrast agent analog of iopamidol but containing a single set of amide protons, both in vitro and in vivo.

Insight into the molecular properties of Chitlac, a chitosan derivative for tissue engineering.

Chitlac is a biocompatible modified polysaccharide composed of a chitosan backbone to which lactitol moieties have been chemically inserted via a reductive N-alkylation reaction with lactose. The physical-chemical and biological properties of Chitlac that have been already reported in the literature suggest a high accessibility of terminal galactose in the lactitol side chain. This finding may account for its biocompatibility which makes it extremely interesting for the production of biomaterials. The average structure and the dynamics of the side chains of Chitlac have been studied by means of NMR (nuclear Overhauser effect and nuclear relaxation) and molecular dynamics to ascertain this hypothesis. A complete assignment of the (1)H and (13)C NMR signals of the modified polysaccharide has been accomplished together with the determination of the apparent pKa values of the primary and secondary amines (6.69 and 5.87, respectively). NMR and MD indicated a high mobility of Chitlac side chains with comparable average internuclear distances between the two techniques. It was found that the highly flexible lactitol side chain in Chitlac can adopt two distinct conformations differing in the orientation with respect to the polysaccharide chain: a folded conformation, with the galactose ring parallel to the main chain, and an extended conformation, where the lactitol points away from the chitosan backbone. In both cases, the side chain resulted to be highly hydrated and fully immersed in the solvent.

Dissociation kinetics of open-chain and macrocyclic gadolinium(III)-aminopolycarboxylate complexes related to magnetic resonance imaging: catalytic effect of endogenous ligands.

The kinetics of the metal exchange reactions between open-chain Gd(DTPA)(2-) and Gd(DTPA-BMA), macrocyclic Gd(DOTA)(-) and Gd(HP-DO3A) complexes, and Cu(2+)  ions were investigated in the presence of endogenous citrate, phosphate, carbonate and histidinate ligands in the pH range 6-8 in NaCl (0.15 M) at 25 °C. The rates of the exchange reactions of Gd(DTPA)(2-) and Gd(DTPA-BMA) are independent of the Cu(2+) concentration in the presence of citrate and the reactions occur via the dissociation of Gd(3+)  complexes catalyzed by the citrate ions. The HCO(3)(-)/CO(3)(2-) and H(2)PO(4)(-) ions also catalyze the dissociation of complexes. The rates of the dissociation of Gd(DTPA-BMA), catalyzed by the endogenous ligands, are about two orders of magnitude higher than those of the Gd(DTPA)(2-). In fact near to physiological conditions the bicarbonate and carbonate ions show the largest catalytic effect, that significantly increase the dissociation rate of Gd(DTPA-BMA) and make the higher pH values (when the carbonate ion concentration is higher) a risk-factor for the dissociation of complexes in body fluids. The exchange reactions of Gd(DOTA)(-) and Gd(HP-DO3A) with Cu(2+) occur through the proton assisted dissociation of complexes in the pH range 3.5-5 and the endogenous ligands do not affect the dissociation rates of complexes. More insights into the interaction scheme between Gd(DTPA-BMA) and Gd(DTPA)(2-) and endogenous ligands have been obtained by acquiring the (13)C NMR spectra of the corresponding diamagnetic Y(III)-complexes, indicating the increase of the rates of the intramolecular rearrangements in the presence of carbonate and citrate ions. The herein reported results may have implications in the understanding of the etiology of nephrogenic systemic fibrosis, a rare disease that has been associated to the administration of Gd-containing agents to patients with impaired renal function.

Image guided therapy: the advent of theranostic agents.

Theranostic agents represent a recently introduced class of imaging probes designed to offer to pharmacologists and physicians a robust tool for minimally invasive in vivo visualization of drug delivery/release and therapy monitoring. By means of these agents, novel strategies able to integrate diagnosis and therapy could be developed. This highly interdisciplinary research field is one of the more innovative products resulting from the synergism between molecular imaging and nanomedicine. Potential applications of theranosis include the in vivo assessment of drug biodistribution and accumulation at the target site, visualization of the drug release from a given nanocarrier, and real-time monitoring of the therapeutic outcome. The expected end-point of theranostic agents is to provide a fundamental support for the optimization of innovative diagnostic and therapeutic strategies that could contribute to emerging concepts in the field of the "personalized medicine". This perspective paper aims at providing the reader the basic principles of theranosis with a particular emphasis to the design of theranostic agents.

Understanding the structural specificity of Tn antigen for its receptor: an NMR solution study.

The present work aims at understanding the structural basis of the biological recognition of Tn antigen (GalNAc-α-O-L-Ser), a specific epitope expressed by tumor cells, and the role of its amino acidic moiety in the interaction with its receptor (the isolectin B4 extracted from Vicia villosa). An NMR structural characterization of the α and ß anomers, based on J couplings and molecular modeling revealed a structure in very good agreement with data reported in literature for variants of the same molecules. In order to demonstrate the involvement of the amino acid in the ligand-receptor recognition, also GalNAc-α-O-D-Ser was studied; the change in the stereochemistry is in fact expected to impact on the interaction only in case the serine is part of the epitope. Relaxation properties in the presence of the receptor clearly indicated a selective recognition of the natural L form, probably due to the formation of a water-mediated hydrogen bond with Asn 129 of the protein.

Stevens rearrangement as a tool for the structural modification of polyaminopolycarboxylic ligands.

Polyaminopolycarboxylic acids are a well known class of ligands employed for metal ion complexation. Despite the large commercial availability, reports of their use as substrates for direct structural modifications are rare. Herein we report a simple and efficient protocol for the preparation of substituted polyaminopolycarboxylic ligands relying on a one-pot N-alkylation-Stevens rearrangement cascade.

Iopamidol as a responsive MRI-chemical exchange saturation transfer contrast agent for pH mapping of kidneys: In vivo studies in mice at 7 T.

Iopamidol (Isovue®-Bracco Diagnostic Inc.) is a clinically approved X-Ray contrast agent used in the last 30 years for a wide variety of diagnostic applications with a very good clinical acceptance. Iopamidol contains two types of amide functionalities that can be exploited for the generation of chemical exchange saturation transfer effect. The exchange rate of the two amide proton pools is markedly pH-dependent. Thus, a ratiometric method for pH assessment has been set-up based on the comparison of the saturation transfer effects induced by selective irradiation of the two resonances. This ratiometric approach allows to rule out the concentration effect of the contrast agent and provides accurate pH measurements in the 5.5-7.4 range. Upon injection of Iopamidol into healthy mice, it has been possible to acquire pH maps of kidney regions. Furthermore, it has been also shown that the proposed method is able to report about pH-changes induced in control mice fed with acidified or basified water for a period of a week before image acquisition.

Methods for an improved detection of the MRI-CEST effect.

CEST imaging is a recently introduced MRI contrast modality based on the use of endogenous or exogenous molecules whose exchangeable proton pools transfer saturated magnetization to bulk water, thus creating negative contrast. One of the critical issues for further development of these agents is represented by their limited sensitivity in vivo. The aim of this work is to improve the detection of CEST agents by exploring new approaches through which the saturation transfer (ST) effect can be enhanced. The performance of the proposed methods has been tested in vitro and in vivo using highly sensitive and highly shifted lipoCEST agents, and the results were compared with the standard ST evaluation mode. The acquired Z-spectra were interpolated locally and voxel-by-voxel by smoothing splines. Besides expressing the ST in the standard mode, we explore two methods, enhanced and integral ST, which better exploit all the information contained in the Z-spectrum. By combining different modes for ST assessment a significant improvement in the detection of the lipoCEST agents, both in vitro and in vivo, has been found. The results obtained from the application of the proposed methods outline the importance of post-processing analysis for highlighting the CEST-MRI contrast.

Design, synthesis, biological evaluation, and NMR studies of a new series of arylsulfones as selective and potent matrix metalloproteinase-12 inhibitors.

Overexpression of macrophage elastase (MMP-12), a member of the matrix metalloproteinases family, can be linked to tissue remodeling and degradation in some inflammatory processes, such as chronic obstructive pulmonary disease (COPD), emphysema, rheumatoid arthritis (RA), and atherosclerosis. On this basis, MMP-12 can be considered an attractive target for studying selective inhibitors that are useful in the development of new therapies for COPD and other inflammatory diseases. We report herein the design, synthesis, and in vitro evaluation of a new series of compounds, possessing an arylsulfonyl scaffold, for their potential as selective inhibitors of MMP-12. The best compound in the series showed an IC50 value of 0.2 nM, with good selectivity over MMP-1 and MMP-14. A docking study was carried out on this compound in order to investigate its binding interactions with MMP-12, and NMR studies on the complex with the MMP-12 catalytic domain were able to validate the proposed binding mode.

A newly generated functional antibody identifies Tn antigen as a novel determinant in the cancer cell-lymphatic endothelium interaction.

Malignant transformation of epithelial cells is frequently associated with the alteration of glycosylation pathways. Tn is a common tumor-associated carbohydrate antigen present in 90% of human carcinomas and its expression correlates with metastatic potential and poor prognosis. Despite its relevance, the functional role of Tn in tumor biology has not been firmly established probably for the lack of appropriate experimental tools. Our aims were to produce highly reactive monoclonal antibodies against Tn making use of synthetically produced Tn and to test their usefulness for in vivo imaging as well as to define their potential functional activity in tumor cell spread. We immunized mice with Tn clustered on cationized BSA and screened the positive hybridomas with Tn-biotinylated alginate. Enzyme-linked immuno sorbent assay and immunofluorescence assays revealed that the most reactive anti-Tn IgM mAb (2154F12A4) selectively recognized Tn on the MCF7 breast cancer cell line since its binding to the cell membrane was completely abolished by preincubation with purified Tn. Importantly, QDot 800-conjugated mAb injected in MCF7-tumor bearing mice specifically bound to primary tumor lesions as well as to metastases in lymph nodes. In addition, this mAb was able to inhibit cancer cell adhesion to lymphatic endothelium suggesting a novel involvement of Tn in the lymphatic dissemination of cancer cells and hypothesizing future applications in inhibiting lymphatic metastases.

Equilibrium and kinetic properties of the lanthanoids(III) and various divalent metal complexes of the heptadentate ligand AAZTA.

The heptadentate ligand 1,4-bis(hydroxycarbonylmethyl)-6-[bis(hydroxycarbonylmethyl)]amino-6-methylperhydro-1,4-diazepine (AAZTA) and its derivatives were recently reported to give stable complexes with Gd(3+) with superior efficiency as MRI contrast agents. Nevertheless, only preliminary data are available on the coordination behavior of this interesting ligand. In this work, thermodynamic and kinetic stability data are determined for the formation of complexes with AAZTA and the lanthanoid metal ions, and other divalent metal ions of interest for this application. The AAZTA ligand binds the lanthanoid ions with log K(ML) values of 17.53-21.85 with its affinity steadily increasing from La(3+) to Lu(3+), suggesting that the seven-membered skeleton is better suited to accommodate smaller metal ions. Even though the denticity is lower, the stability of the heavier lanthanoid complexes is comparable to those of the classical ligand diethylenetriaminepentaacetic acid (DTPA). The transmetalation reactions of [Gd(AAZTA)](-) with Cu(2+) and Eu(3+) predominantly occur through proton-assisted dissociation of the complex. The role of the direct attack of Cu(2+) or Eu(3+) in the exchange reactions is limited, although the formation of dinuclear complexes decreases the proton-assisted dissociation. Near physiological conditions, [Gd(AAZTA)](-) is significantly more inert than [Gd(DTPA)](2-), allowing its potentially safe use as contrast agent in magnetic resonance imaging.

3T MRI evaluation of the accuracy of atlas-based subthalamic nucleus identification.

Modulation of the activity of the subthalamic nucleus (STN) using deep brain stimulation (DBS) in patients with advanced Parkinson's disease is the most common procedure performed today by functional neurosurgeons. The STN contours cannot be entirely identified on common 1.5 T images; in particular, the ventromedial border of the STN often blends with the substantia nigra. 3 T magnetic resonance imaging (MRI) provides better resolution and can improve the identification of the STN borders. In this work, we have directly identified the STN using 3 T MR imaging to validate the accuracy of a computer-aided atlas-based procedure for automatic STN identification. Coordinates of the STN were obtained from the Talairach and Tournoux atlas and transformed into the coordinates of the Montreal Neurological Institute (MNI) standard brain volume, creating a mask representation of the STN. 3 T volumetric T1 and T2 weighted (T1w and T2w, respectively) acquisitions were obtained for ten patients. The MNI standard brain volume was registered onto each patient MRI, using a new approach based on global affine, region-of-interest affine, and local nonrigid registrations. The estimated deformation field was then applied to the STN atlas-based mask, providing its location on the patient MRI. The entire procedure required on average about 20 min. Because STN is easily identifiable on 3 T T2w-MRIs, it was manually delineated; the coordinates of the center of mass of the manually and automatically identified structures were compared. Additionally, volumetric overlapping indices were calculated and the spatial relationship between the midcommissural point and the STN center of mass was investigated. All indices indicated, on average, good agreement between manually and automatically identified structures; displacement of the centers of mass of the manually and automatically identified structures was less than or equal to 2.35 mm, and more than 80% of the manually identified volume was covered by the automatic localization, on average. Bland-Altman analysis indicated that the automatic STN identification was within the limits of agreement with the manual localization on 3 T MRIs. Automatic atlas-based STN localization provides an accurate and user-friendly tool and can enhance target identification when 1.5 T scanners with limited capability to identify the STN boundaries are used.

Direct validation of atlas-based red nucleus identification for functional radiosurgery.

Treatment targets in functional neurosurgery usually consist of selected structures within the thalamus and basal ganglia, which can be stimulated in order to affect specific brain pathways. Chronic electrical stimulation of these structures is a widely used approach for selected patients with advanced movement disorders. An alternative therapeutic solution consists of producing a lesion in the target nucleus, for example by means of radiosurgery, a noninvasive procedure, and this prevents the use of intraoperative microelectrode recording as a method for accurate target definition. The need to have accurate noninvasive localization of the target motivated our previous work on atlas-based identification; the aim of this present work is to provide additional validation of this approach based on the identification of the red nuclei (RN), which are located near the subthalamic nucleus (STN). Coordinates of RN were obtained from the Talairach and Tournoux (TT) atlas and transformed into the coordinates of the Montreal Neurological Institute (MNI) atlas, creating a mask representation of RN. The MNI atlas volume was nonrigidly registered onto the patient magnetic resonance imaging (MRI). This deformation field was then applied to the RN mask, providing its location on the patient MRI. Because RN are easily identifiable on 1.5 T T2-MRI images, they were manually delineated; the coordinates of the centers of mass of the manually and automatically identified structures were compared. Additionally, volumetric overlapping indices were calculated. Ten patients were examined by this technique. All indices indicated a high level of agreement between manually and automatically identified structures. These results not only confirm the accuracy of the method but also allow fine tuning of the automatic identification method to be performed.

BOLD fMRI integration into radiosurgery treatment planning of cerebral vascular malformations.

Functional magnetic resonance imaging (fMRI) is used to distinguish areas of the brain responsible for different tasks and functions. It is possible, for example, by using fMRI images, to identify particular regions in the brain which can be considered as "functional organs at risk" (fOARs), i.e., regions which would cause significant patient morbidity if compromised. The aim of this study is to propose and validate a method to exploit functional information for the identification of fOARs in CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery treatment planning; in particular, given the high spatial accuracy offered by the CyberKnife system, local nonrigid registration is used to reach accurate image matching. Five patients affected by arteriovenous malformations (AVMs) and scheduled to undergo radiosurgery were scanned prior to treatment using computed tomography (CT), three-dimensional (3D) rotational angiography (3DRA), T2 weighted and blood oxygenation level dependent echo planar imaging MRI. Tasks were chosen on the basis of lesion location by considering those areas which could be potentially close to treatment targets. Functional data were superimposed on 3DRA and CT used for treatment planning. The procedure for the localization of fMRI areas was validated by direct cortical stimulation on 38 AVM and tumor patients undergoing conventional surgery. Treatment plans studied with and without considering fOARs were significantly different, in particular with respect to both maximum dose and dose volume histograms; consideration of the fOARs allowed quality indices of treatment plans to remain almost constant or to improve in four out of five cases compared to plans with no consideration of fOARs. In conclusion, the presented method provides an accurate tool for the integration of functional information into AVM radiosurgery, which might help to minimize undesirable side effects and to make radiosurgery less invasive.