Gadolinium Complexes as Contrast Agent for Cellular NMR Spectroscopy

Abstract

Aqua Gd3+ and Gd-DOTA (gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacete) complexes were studied as a contrast agent in cellular NMR (nuclear magnetic resonance) spectroscopy for distinguishing between intracellular and extracellular spaces. The contrast agents for this purpose should provide strong paramagnetic relaxation enhancement and localize in the extracellular space without disturbing biological functions. Cell membrane permeability to Gd complexes was evaluated from the concentrations of gadolinium complexes in the inside and outside of E. coli cells measured by the 1H-NMR relaxation. The site-specific binding of the complexes to E. coli cells was also analyzed by high-resolution solid-state 13C-NMR. The aqua Gd3+ complex did not enhance T1 relaxation in proportion to the amount of added Gd3+. This Gd3+ concentration dependence and the 13C-NMR indicated that its strong cytotoxicity should be due to the binding of the paramagnetic ions to cellular components especially at the lipid membranes. In contrast, Gd-DOTA stayed in the solution states and enhanced relaxation in proportion to the added amount. This agent exhibited strong T1 contrast between the intra- and extracellular spaces by a factor of ten at high concentrations under which the cells were viable over a long experimental time of days. These properties make Gd-DOTA suitable for selectively contrasting the living cellular space in NMR spectroscopy primarily owing to its weak interaction with cellular components.

Gadolinium-Based Paramagnetic Relaxation Enhancement Agent Enhances Sensitivity for NUS Multidimensional NMR-Based Metabolomics

“…Gadolinium-based contrast agents have been widely used in MRI diagnostic imaging, for studying soluble proteins, for characterizing protein-protein, protein-oligosaccharides, and protein-nucleic acid complexes, and for investigating membrane proteins using NMR spectroscopy [ 26 , 27 ]. Sakol et al have also shown the utility of the Gd-based contrast agent, Gd-DOTA, for cellular localization studies using NMR spectroscopy [ 28 ]. Similarly, Mulder and colleagues utilized gadolinium-based PRE agents and achieved a 3- to 4-fold improvement in acquisition time for quantifying several plasma metabolites [ 17 ].…”

“…The decrease in T 1 and T 2 rates depends on the contrast agent used and its concentration, the charge state of the compound, the viscosity of the solution, and the protein affinity of either the compound or contrast agent, among other issues. The typical range of T 1 values for nuclei of common metabolites such as glucose, lactate, citrate, acetate, glutamine, and alanine are between 0.9 and 4 s. Similarly, T 2 values range from 100 to 600 ms [ 17 , 28 , 29 ]. In the presence of Gd, T 1 values can decrease from 2- to 10-fold depending on the concentration of Gd.…”

Clickable Radiocomplexes With Trivalent Radiometals for Cancer Theranostics: In vitro and in vivo Studies

“…The macrocycle DOTA is considered one of the gold standards in nuclear medicine and in the last 25 years, DOTAbased chelators had a tremendous impact in various medical imaging modalities such as PET, SPECT, MRI and fluorescence imaging (6). Its widespread use is mainly due to its versatility that allows the complexation of different metal ions, but also to its easy functionalization, allowing the most diversified pre-clinical and clinical applications (7)(8)(9)(10).…”

Special Issue “Selected Papers from the 8th Asia-Pacific NMR (APNMR) Symposium: Recent Advances in NMR Spectroscopy”

“…These articles showcase recent advancements in the broader field of NMR. Fujiwara and coworkers work on emerging cellular NMR spectroscopy that has implications in elucidating structures and dynamics in native cellular environments [ 1 ]. These authors investigate contrast agents Gd 3+ and Gd-DOTA (gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacete) probing molecules in E. coli cells in situ [ 1 ].…”

“…Fujiwara and coworkers work on emerging cellular NMR spectroscopy that has implications in elucidating structures and dynamics in native cellular environments [ 1 ]. These authors investigate contrast agents Gd 3+ and Gd-DOTA (gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacete) probing molecules in E. coli cells in situ [ 1 ]. Broker, Tompa, and coworkers construct melting diagrams, using a wide line NMR method, of intrinsically disordered pathogenic protein alpha-synuclein [ 2 ].…”