Contrast agent for tumor diagnostics: Phosphorescent metal-organic coordination polymers for optical imaging

Mar 23, 2011
Contrast agent for tumor diagnostics: Phosphorescent metal-organic coordination polymers for optical imaging

(PhysOrg.com) -- X-rays are not the only way: visible and especially infrared light can also be used to image human tissue. The effectiveness of optical imaging processes can be significantly improved with suitable dyes used as contrast agents. In the journal Angewandte Chemie, a team led by Wenbin Lin at the University of North Carolina has now introduced a novel contrast agent that marks tumor cells in vitro. The dye is a phosphorescent ruthenium complex incorporated into nanoparticles of a metal–organic coordination polymer, which allows an extraordinarily high level of dye loading.

Fluorescent dyes accumulate in varying amounts in different types of tissue. Such contrast agents make it possible to use to differentiate between healthy and tumorous tissue. However, this method is limited by the fact that very high concentrations of dye are needed to produce sufficiently strong fluorescence. Organic dye molecules packed at high concentrations into nanocapsules tend to quench each other’s fluorescence. Materials that fluoresce more strongly, such as quantum dots, are often not biocompatible.

This team has now developed an alternative: metal complexes connected to form lattice-like coordination polymers. Coordination polymers are metal–organic structures consisting of metal ions, which act as connecting points, linked by bridges made of organic molecules or coordination complexes. The scientists made such polymers with bridges consisting of a light-emitting complex of the metal ruthenium. Zirconium ions proved to be suitable connecting points. These tiny structures form spherical nanoparticles.

The complexes do not fluoresce, but rather phosphoresce, which means that they emit light for a proportional length of time after irradiation with light. Because they are not placed inside a nano-transport container, but are a component of the nanoparticle, it is possible to attain a very high level of dye loading—in this instance over 50 %. Quenching of the phosphorescence at high concentrations does not occur in such complexes.

In order to prevent the glowing particles from rapidly dissolving and to increase the biocompatibility, they were coated with thin layers of silicon dioxide and a layer of polyethylene glycol. The latter acts as an anchor point for anisamide, a molecule that specifically binds to receptors that are far more common on the surfaces of many types of tumor cell than on healthy cells.

In a cell culture, it was possible to selectively mark a line of cancer cells with the phosphorescent . The researchers hope that it will be possible to develop for the use of optical imaging for tumor detection based on these new metal–organic nanomaterials.

Explore further: Nanocontainers for nanocargo: Delivering genes and proteins for cellular imaging, genetic medicine and cancer therapy

More information: Wenbin Lin et al., Phosphorescent Nanoscale Coordination Polymers as Contrast Agents for Optical Imaging, Angewandte Chemie International Edition, dx.doi.org/10.1002/anie.201008277

Related Stories

A Good Eye for Oxygen

Mar 27, 2009

(PhysOrg.com) -- We cannot live without it; yet too much of it causes damage: oxygen is a critical component of many physiological and pathological processes in living cells. Oxygen deficiency in tissues is thus related to ...

Four-in-One: Targeted Gene Suppression in Cancer Cells

May 06, 2009

(PhysOrg.com) -- Diagnosis and treatment in one go: Korean researchers led by Tae Gwan Park and Jinwoo Cheon have developed the basis for a four-in-one agent that can detect, target, and disable tumor cells while also making ...

Self-Assembling Nanoparticles Image Tumor Cells

Jul 23, 2007

By taking advantage of the full range of ways in which molecules can interact with and bind to one another, a team of investigators at the Carolina Center of Cancer Nanotechnology Excellence has created nanoparticles that ...

Recommended for you

Engineered proteins stick like glue—even in water

21 hours ago

Shellfish such as mussels and barnacles secrete very sticky proteins that help them cling to rocks or ship hulls, even underwater. Inspired by these natural adhesives, a team of MIT engineers has designed ...

Smallest possible diamonds form ultra-thin nanothreads

21 hours ago

For the first time, scientists have discovered how to produce ultra-thin "diamond nanothreads" that promise extraordinary properties, including strength and stiffness greater than that of today's strongest ...

A nanosized hydrogen generator

Sep 20, 2014

(Phys.org) —Researchers at the US Department of Energy's (DOE) Argonne National Laboratory have created a small scale "hydrogen generator" that uses light and a two-dimensional graphene platform to boost ...

User comments : 0