Mark Woods

Bio: Mark Woods is an academic researcher from Oregon Health & Science University. The author has contributed to research in topics: DOTA & Coordination geometry. The author has an hindex of 30, co-authored 70 publications receiving 4239 citations. Previous affiliations of Mark Woods include University of Texas at Dallas & Claude Bernard University Lyon 1.

Non-radiative deactivation of the excited states of europium, terbium and ytterbium complexes by proximate energy-matched OH, NH and CH oscillators: an improved luminescence method for establishing solution hydration states

Abstract: The radiative rate constants for depopulation of the excited states of closely-related series of anionic, neutral and cationic europium, terbium and ytterbium complexes have been measured in H2O and D2O. With the aid of selective ligand deuteriation, the relative contributions of OH, NH (both amide and amine) and CH oscillators have been measured and critically assessed. Quenching of the Eu 5D0 excited state by amine NH oscillators is more than twice as efficient as OH quenching. The importance of the distance between the excited Ln ion and the XH oscillator is described with recourse to published crystallographic information. The general equation, q = A′(ΔkH2O–kD2O)corr is presented and revised values of A′ for Eu (1.2 ms), Tb (5 ms) and Yb (1 µs) given, which allow for the quenching contribution of closely diffusing OH oscillators. The relevance of such studies to the hydration state of certain gadolinium complexes is described and clear evidence provided for a break in hydration at gadolinium.

Paramagnetic lanthanide complexes as PARACEST agents for medical imaging

Abstract: This tutorial review examines the fundamental aspects of a new class of contrast media for MRI based upon the chemical shift saturation transfer (CEST) mechanism. Several paramagnetic versions called PARACEST agents have shown utility as responsive agents for reporting physiological or metabolic information by MRI. It is shown that basic NMR exchange theory can be used to predict how parameters such as chemical shift, bound water lifetimes, and relaxation rates can be optimized to maximize the sensitivity of PARACEST agents.

Chemical Exchange Saturation Transfer Contrast Agents for Magnetic Resonance Imaging

Abstract: Magnetic resonance imaging (MRI) contrast agents have become an important tool in clinical medicine. The most common agents are Gd(3+)-based complexes that shorten bulk water T(1) by rapid exchange of a single inner-sphere water molecule with bulk solvent water. Current gadolinium agents lack tissue specificity and typically do not respond to their chemical environment. Recently, it has been demonstrated that MR contrast may be altered by an entirely different mechanism based on chemical exchange saturation transfer (CEST). CEST contrast can originate from exchange of endogenous amide or hydroxyl protons or from exchangeable sites on exogenous CEST agents. This has opened the door for the discovery of new classes of responsive agents ranging from MR gene reporter molecules to small molecules that sense their tissue environment and respond to biological events.

NMR, Relaxometric, and Structural Studies of the Hydration and Exchange Dynamics of Cationic Lanthanide Complexes of Macrocyclic Tetraamide Ligands

Abstract: The solution structure and dynamics of metal-bound water exchange have been investigated in a series of lanthanide complexes of primary, secondary, and tertiary tetraamide derivatives of 1,4,7,10-tetraazacyclododecane In the gadolinium complexes at ambient pH, water exchange lifetimes (τm) determined by 17O NMR were sufficiently long (19 μs for [Gd·2]3+, 298 K, 17 μs for [Gd·3]3+, and 8 μs for [Gd·4]3+) to limit the measured relaxivity Direct 1H NMR observation of the bound water resonance is possible for the corresponding Eu complexes at low temperature in CD3CN, and the rate of water proton exchange is about 50 times faster in the twisted square antiprismatic isomer (m) than in the isomeric square antiprismatic (M) complex The ratio of these two isomers in solution is sensitive to the steric demand of the amide substituent, with m/M = 2 for [Eu·4]3+, but 025 for [Eu·2]3+ The slowness of coordinated water exchange has allowed the rate of prototropic exchange to be studied: in basic media deprotonat

Correlation of Water Exchange Rate with Isomeric Composition in Diastereoisomeric Gadolinium Complexes of Tetra(carboxyethyl)dota and Related Macrocyclic Ligands

Abstract: The solution structure and dynamics of metal-bound water exchange have been studied in a series of diastereoisomeric gadolinium complexes of tetra(carboxyethyl) derivatives of 1,4,7,10-tetraazacyclodecane. The structures of the (RRRS), (RSRS), and (RRSS) ligands and the Eu, Gd, and Tb complexes of the (RRRR) isomer have been determined by X-ray crystallography. Luminescence measurements on the Eu and Tb complexes revealed an integral hydration state (q = 1) in each case for the Eu isomers, whereas nonintegral values were measured for the (RRRR) and (RRRS) Tb isomers (e.g., [(RRRR)-Tb·1]-, q = 0.60). The ratio of the twisted and regular monocapped square antiprismatic isomers has been measured in solution by 1H NMR for the Eu and Tb complexes and followed the order, (RRRR) > (RRRS) > (RSRS) > (RRSS). Water exchange rates in the gadolinium complexe have been determined by 17O NMR and were fastest for the (RRRR) isomer [τm = 68 ns (298 K)] and correlated very well with the proportion of the twisted square an...

Taking advantage of luminescent lanthanide ions

Abstract: Lanthanide ions possess fascinating optical properties and their discovery, first industrial uses and present high technological applications are largely governed by their interaction with light. Lighting devices (economical luminescent lamps, light emitting diodes), television and computer displays, optical fibres, optical amplifiers, lasers, as well as responsive luminescent stains for biomedical analysis, medical diagnosis, and cell imaging rely heavily on lanthanide ions. This critical review has been tailored for a broad audience of chemists, biochemists and materials scientists; the basics of lanthanide photophysics are highlighted together with the synthetic strategies used to insert these ions into mono- and polymetallic molecular edifices. Recent advances in NIR-emitting materials, including liquid crystals, and in the control of luminescent properties in polymetallic assemblies are also presented. (210 references.)

Lanthanide luminescence for functional materials and bio-sciences

Abstract: Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

Lanthanide Luminescence for Biomedical Analyses and Imaging

Abstract: Keywords: Time-Resolved Fluorescence ; Resonance Energy-Transfer ; Near-Infrared Luminescence ; Double-Stranded Dna ; Prostate-Specific Antigen ; Photoinduced Electron-Transfer ; Europium-Tetracycline Complex ; Sybr-Green-I ; Terbium Complexes ; Optical Probes Reference EPFL-ARTICLE-149396doi:10.1021/cr900362eView record in Web of Science Record created on 2010-06-17, modified on 2017-05-12

Inorganic Nanoparticles for MRI Contrast Agents

Abstract: Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site-specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle-based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle-based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle-based MRI contrast agents.