Light used to activate drugs in lab

The Daily Telegraph has reported the development of a new cancer treatment “that uses light to target tumour cells”. The newspaper explained that researchers have “created a drug that is packed with light-sensitive molecules that accumulate around cancer cells. When light is shone through the tumour, the molecules are activated and kill the cancer cells.”

The news comes after scientists performed a laboratory study in which they produced a new type of tiny, light-sensitive particle that could enter laboratory-grown cancer cells. The researchers found that their "nanoparticles" could enter human colon cancer cells grown in a laboratory, and that when the particles were stimulated by light, they could kill these cancer cells.

The direct implications for humans of this very early experimental study are currently limited. Further basic research is needed to assess a number of important issues, such as whether it is possible to use these particles to target cancer cells, avoiding healthy cells.

Where did the story come from?

The study was carried out by researchers from the University of Hull. The research paper did not state any sources of funding for the research. The study was published in the peer-reviewed scientific journal Molecular Pharmaceutics .

The Daily Telegraph did a good job of explaining the principles of using light-sensitive nanoparticles to target cancer, but the article did not emphasise that this was an experimental study conducted on cells in culture.

What kind of research was this?

This laboratory research combined two different experimental treatment technologies: light-activated drugs and tiny nanoparticles, which can be used to help deliver drugs to specific types of cells within the body. Nanoparticles are very tiny particles, typically one-millionth of a millimetre in size. They can potentially contain a drug and can be surrounded by a chemical shell that targets the drug towards a particular cell type. In this case, the nanoparticles contained a chemical that was activated by light to produce toxic substances to potentially kill cells. These types of light-activated chemicals have been used in a treatment called photodynamic therapy.

The researchers wanted to see whether they could make nanoparticles containing light-activated chemicals that could be taken up by cancer cells, and to test whether they would kill the cancerous cells when exposed to a particular wavelength of light.

What did the research involve?

The researchers developed two types of nanoparticles, one of which was on average 45-billionths of a metre wide, the other about 95-billionths of a metre wide.

The two types of nanoparticles contained chemicals that are activated by light (photosensitizer chemicals) on their outside shell. One type contained one photosensitizer (PCNP) and the other contained two photosensitizers (PCNP-P)

The nanoparticles fluorescently glowed when light was shone on them. The researchers looked at the proportion of cells which were fluorescent after treatment to see whether human colon cancer cells grown in the laboratory would take up the nanoparticles. They did this using a very high-resolution microscope that could detect a fluorescent signal.

The researchers said that when the photosensitizing chemicals were activated by light, they produced toxic chemicals called “reactive oxygen species”. After they added the nanoparticles to the cancer cells, they shone light on them and recorded whether the treatment caused the cancer cells to die.

What were the basic results?

The researchers found that the colon cancer cells in culture were able to take up the fluorescent particles. After 18 hours, the strength of the florescent signal given off suggested that maximum uptake had occurred.

After the researchers treated the cells with nanoparticles for 25 hours, they activated the cells with two doses of light for around 23 minutes. They measured the amount of cell death 18–24 hours later. They found that for cells that had been exposed to the particles but not to light, there was around 20–30% cell death in this period, but for light-exposed cells there was 70–90% cell death.

How did the researchers interpret the results?

The researchers said that their nanoparticles have potential as “delivery vehicles for photodynamic therapy for cancer”.

Conclusion

This laboratory study has developed a way to make a new type of tiny particle, called nanoparticles, that could be selectively activated by exposure to light. It then assessed whether the nanoparticles could enter and kill a type of colon cancer cell when exposed to light.

While this is certainly an intriguing idea, it is too early to say whether these particles could be used as a therapy for cancer. Further basic research would be needed to see if it is possible to target the particles at cancer cells and to make sure they avoid healthy cells. This study only looked at their uptake within a sample of cancer cells.

The production of nanoparticles for delivering drugs is a growing area of chemistry and pharmacy research. However, this technology is still in its early stages and the direct implications of this research for cancer treatment are currently limited.