MR Imaging

As a medical imaging technique, unlike computerized tomography (CT) and positron emission tomography (PET), magnetic resonance imaging (MRI) does not involve x-rays or use ionizing radiation. Compared to CT, MRI provides better contrast in images of soft tissue, such as the brain or abdomen. As one of the most comprehensive and widely used clinical diagnostic tools, MRI provides very detailed images of soft tissue anatomy with high spatial resolution, infinite penetration depth, long effective imaging window, rapid in vivo imaging acquisition and no ionizing radiation. Therefore, MRI is mainly used for the non-invasive diagnosis of tumors. As a polymer with great potential in nanomedicine, the unique properties of dendrimers, including rigidity, oligomeric dispersion, and easy surface modification, make them particularly suitable for MRI imaging. Current dendrimer-based macromolecules for MRI imaging include, blood pool imaging agents, lymph node imaging agents, tumor-targeting therapeutic agents and cell tracking agents.

MRI - A Powerful Non-invasive Diagnostic Tool

Methods used for structural/anatomical imaging include CT, MRI, or ultrasound (US) with relatively high spatial resolution; methods used for functional imaging include optical imaging (OI), PET and single photon emission tomography (SPECT), which are well suited to detect molecular and cellular changes in disease. Among all imaging methods, MRI is recognized as one of the most widely used medical imaging techniques for clinical applications because of its high penetration depth, good soft tissue differentiation, high spatial resolution, and safety from ionizing radiation. MRI is a convenient and noninvasive imaging modality that is widely used in clinical practice. Although MRI is a powerful, non-invasive, and commonly used medical diagnostic tool, direct application of contrast agent to tissues has some drawbacks and putting the contrast agent into a nanocarrier can solve many problems. Cancer therapeutic diagnostics is one of the most important methods for early detection and treatment of patients, and nanoparticles are used as potential carriers for cancer therapeutic diagnostics.

Dendrimers as MRI Contrast Agents

Dendrimers consist of 3 main parts: the core, the interior, and the surface branches. Dendrimers have multiple functional groups branching on their surfaces, giving them great potential as MRI contrast agents. As a nanoparticle, dendrimers have features such as precise nanoscale scaffolds and nanocontainers that have great potential for drug delivery. When dendrimers are properly labeled, they can be used as biomarkers for molecular imaging. MRI contrast agents based on dendrimers have great potential for clinical applications due to their flexible nature and unique high relativity that minimizes the total dose without compromising image quality and reduces the risk of toxicity.

Advantages of Dendrimers as MRI Contrast Agents

Core types of dendrimers include ethylene diamine (EDA), diaminobutyl (DAB), polyamidoamine (PAMAM), and polypropylimine (PPI). Cores currently used for MRI imaging agents include PAMAM or PPI dendrimers, which are highly soluble in aqueous solutions, usually have a surface rich in primary amines. The enriched primary amine functional groups on the outer shell provide attachment points for chelates that bind gadolinium to act as signal beacons or for binding targeting molecules, such as antibodies, for site-specific targeting. In addition, the bifunctional surfaces of DAB/PPI and PAMAM dendrimers have both targeting and chelating capabilities, driving the use of dendrimers as contrast agents for molecular imaging. When used as MRI contrast agents, dendrimers offer many distinct advantages over lower molecular weight gadolinium chelates, including enhanced r1 relaxation due to slow rotational kinetics and tunable pharmacokinetics for blood pool, liver, kidney, and lymphatic imaging. In addition, dendrimers can be flexibly labeled due to their inherent multivalency.

Dendrimers-based contrast agents for MRI of glioblastoma. (McMahon MT, et al., 2018)

How We Can Help

With our advanced technology platform and extensive experience, CD BioSciences provides innovative dendrimer products and high quality services to passionate researchers worldwide. Our dedicated scientists will address each of your specific needs and overcome all obstacles in your dendrimer project. If you are interested in our services or have any other questions, please feel free to contact us.

Reference

1. McMahon MT.; Bulte JWM. Two decades of dendrimers as versatile MRI agents: a tale with and without metals. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2018, 10: e1496.