A new idea to kill tumour cells with the help of nanoparticles and light has been mooted by University of Virginia medical physicists.
The experts say that their approach employs quantum dots, semiconductor nanostructures that can confine electrons in three dimensions and emit light when exposed to ultraviolet radiation.
Wensha Yang, an instructor in radiation oncology at the university, and his colleagues have found that quantum dots also give off light when exposed to megavoltage x-rays, such as those used in cancer radiotherapy.
According to them, this property makes quantum dots an ideal mediator in therapies employing light-activated compounds to treat cancer.
The scientists have revealed that their technique combines the photosensitizer that is currently used to treat certain kinds of shallowly located tumours, called Photofrin, with quantum dots.
Photofrin is absorbed by cancer cells, and kills cells when activated by exposure to light.
Yang and his colleagues believe that combining Photofrin and quantum dots may create an efficient method to kill even deeply seated cancer cells.
They say that exposure to high doses of radiation would cause the dots to become luminescent and emit light, which in turn would trigger the cancer-killing activity of the Photofrin.
Although the researchers have thus far studied this theory only in cancer cells grown in culture, they think it may work on tumours located too deep within the body to be reached by an external light source.
The researchers also say that the treatment would not harm normal tissues because the toxicity of the quantum dot-Photofrin conjugate is only activated when radiation is applied.
Also, the area to be treated is targeted with conformal radiation, which is delivered with high precision within the three-dimensional contours of the tumour, with minimal spillover to surrounding healthy tissues.
Consequently, Yang says, "the toxicity of the drug is substantially lower in the lower radiation dose area" outside the boundaries of the tumour.
In tests on human lung carcinoma cells, the process resulted in a two-six times lower tumour cell survival compared to radiation alone, but with minimal toxicity to nearby cells.