Researchers enhance DNA-targeted anti-cancer drugs
molecules they are creating to deliver medication to cancer cells.
The man-made molecular complexes enter cancer cells and, when
signalled, deliver killing medicine or cause the cell to change.
The scientists are dealing with an age-old problem in which scientists are racing to create ways to deliver cancer-killing drugs to tumours without harming surrounding tissue. This latest research uses Photodynamic therapy (PDT) - a treatment that uses a drug, called a photosensitiser or photosensitising agent, and a particular type of light.
When photosensitisers are exposed to a specific wavelength of light, they produce a form of oxygen that kills nearby cells. Each photosensitiser is activated by light of a specific wavelength. This wavelength determines how far the light can travel into the body.
Thus, doctors use specific photosensitisers and wavelengths of light to treat different areas of the body with PDT.
The new supermolecules have more units that will absorb light - providing more control over the range of light frequencies that can be included and excluded as signals and the responses.
Karen Brewer, professor of chemistry at Virginia Tech, announced the creation of molecular assemblies that solved two challenges facing PDT, or activating drug delivery devices with light.
The Brewer group's systems could be activated by visible light in the therapeutic range - a wavelength not blocked or reflected by tissue. The systems also were able to operate without oxygen.
The group now has more kinds of supramolecular assemblies that absorb therapeutic light and they are adding units to the structure. For instance, they added platinum, a metal with anticancer activity because it binds to DNA inhibiting cell replication.
"Using platinum assures that we are activating complexes that are already attached to the target," said Brewer.
"The previous systems had an association with DNA but could release, which might result in an impact on other parts of the cell."
Because the therapeutic complexes only activate with visible light, the researchers are now able to add a luminescent tag that glows in the presence of ultra violet (UV) light.
"The UV light does not activate the system but will allow us to see such things as how the assembly enters cells and how much of the drug reaches the DNA," she said.
"It is a common practice in the medical field to use luminescent dyes to study cells, so pathology labs will have the equipment needed to monitor drug delivery."
To date, the US Food and Drug Administration (FDA) has approved the photosensitising agent called porfimer sodium, or Photofrin, for use in PDT to treat or relieve the symptoms of oesophageal cancer and non-small cell lung cancer.
Porfimer sodium is approved to relieve symptoms of oesophageal cancer when the cancer obstructs the oesophagus or when the cancer cannot be satisfactorily treated with laser therapy alone.
Porfimer sodium is used to treat non-small cell lung cancer in patients for whom the usual treatments are not appropriate, and to relieve symptoms in patients with non-small cell lung cancer that obstructs the airways.
In 2003, the FDA approved porfimer sodium for the treatment of precancerous lesions in patients with Barrett's oesophagus (a condition that can lead to oesophageal cancer).
