Responsive magnetic resonance imaging contrast agents as chemical sensors for metals in biology and medicine

Abstract

This tutorial review highlights progress in the development of responsive magnetic resonance imaging (MRI) contrast agents for detecting and sensing biologically relevant metal ions. Molecular imaging with bioactivatable MRI indicators offers a potentially powerful methodology for studying the physiology and pathology of metals by capturing dynamic three-dimensional images of living systems for research and clinical applications. This emerging area at the interface of inorganic chemistry and the life sciences offers a broad palette of opportunities for researchers with interests ranging from coordination chemistry and spectroscopy to supramolecular chemistry and molecular recognition to metals in biology and medicine.

Iron(III) Contrast Agent Candidates for MRI: a Survey of the Structure–Effect Relationship in the Last 15 ­Years of Studies

“…10 ns), but that longer water residence in the first coordination sphere decreases the relaxation rate. [15,20,21] Within the inner sphere this distinction of classical coordination was always expressly emphasized. Because the free coordination site is easily identified by the geometry of the coordination polyhedron and supported by X-ray analysis or molecular modeling, an integer number of water molecules replacing one another was presented in the mechanism description.…”

In Vivo Characterization of a Smart MRI Agent That Displays an Inverse Response to Calcium Concentration

“…After 3 h, the organic phase was separated and washed with 2 N HCl (50 mL) and a saturated NaCl solution (50 mL). The organic phase was dried over MgSO 4 and concentrated under reduced pressure. n-Hexane (20 mL) was added to the oil, and the solution was stored at -20°C overnight.…”

Dendrimer-based magnetic resonance imaging agents for brain cancer

“…Much effort has been dedicated to synthesizing MRI agents that respond to biologically important metal ions like Ca 2+ , Zn 2+ , Fe 2+ , and Cu +/2+ [121]. However, only ions with concentrations above the micromolar range can be detected .…”

“…These agents, which are referred to stimulus-responsive or smart contrast agents, are sensitive to specific fluctuations in the local environment, such as pH, biological metal ion concentration or enzymatic activity, and are capable of reporting on such changes by inducing alterations in the MRI signal [119][120][121][122][123][124]. The change in relaxivity of these agents before and after stimulation is the most important factor in evaluating the efficiency of a stimulus-responsive contrast agent [125].…”