• Targeted contrast agents usually have higher relaxivities when interacting with the target due to the restriction of the rotational motion upon binding.
Calix[4]arenes as Molecular Platforms for Magnetic Resonance Imaging (MRI) Contrast Agents
The Paper
Outline
1
Introduction
2
Experimental Section
3
Conclusion
• In MRI an ongoing trend is to apply higher magnetic field strengths (>1.5 T).
• This can be achieved by optimizing the average water residence lifetime tM to even shorter values than that predicted of 20–40 ns for high molecular weight agents.
• Some main imaging techniques
Positron emission tomography (PET) Single photon emission computed tomography (SPECT) Magnetic resonance imaging (MRI) Ultrasonic imaging Optical imaging (Bioluminescence ,Fluorescence )
MRI • Magnetic resonance imaging (MRI) is one of the
most important techniques in medical imaging.
• It is noninvasive, avoids problems occurring in other imaging techniques such as scattering (optical imaging) or high-energy radiation (computed tomography (CT) or X-ray), and enables the production of 3D images of various tissues.
• Aggregation
• Variable-temperature 17O NMR measurements
• Within the experimental error, the hyperfine coupling constant is identical to commonly observed values for oxygen atoms directly coordinated to Gd.
1、 Introduction
• Molecular imaging
It seems to take photos of molecular , display the morphological structure of our target. In other words, characterization and measurement of the process of living animals, human biology and model system in the cellular and molecular level using the imaging detector in vitro . • Features of molecular imaging Non-invasive imaging technique Dynamic acquisition Reflect full-scale
• The challenge is to prepare complexes that do not release the toxic metal ion in vivo and yet are efficient contrast agents.
2、ExHale Waihona Puke erimental Section
• Nuclear magnetic relaxation dispersion
• NMRD is a powerful technique for characterizing MRI contrast agents.
• NMRD profiles show the relaxivity of the monomer to be almost independent of the magnetic field strength up to 60 MHz.
• One of approaches to find systems with optimal τR is to use the rather rigid calix[4]arene core as a synthetic platform.
• Calixarenes generally enable the introduction of at least two different functions.
• The contrast is generated by differences in either the proton density between tissues and/or differences in T1 or T2 relaxation times.
• A noncovalent approach is to prepare amphiphilic compounds that form aggregates.