A new type of treatment called “light-activated drug delivery” is showing promise as a way to give doctors control over precisely where and when drugs are delivered inside the patient’s body. Now, researchers have developed a light-activated way to target cancer cells without hurting healthy tissue by using drug-carrying nanoparticles.
Jeffrey Zink, professor of chemistry and biochemistry, and Fuyu Tamanoi, professor of microbiology, immunology and molecular genetics, both at University of California Los Angeles in the US, and colleagues, report their findings in the journal SMALL.
Their method uses nanoparticles – particles that are so small their size is compatible with cell dimensions – to carry chemotherapy drugs directly to tumor cells and release them when activated by a two-photon laser in the infrared red wavelength.
Not only can the nanoparticles ferry drugs to precisely targeted areas of the body, but they are fluorescent and their progress can be tracked.
This ability to track a targeted therapy is an example of a new blend of therapy and diagnostics, dubbed “theranostics.”
Being able to precisely pinpoint the target in the body so the chemotherapy drug only hits tumor cells and not neighboring healthy tissue, greatly reduces the side effects of treatment and increase a drug’s cancer-killing power.
This study is important because developing a drug delivery system that is triggered by light that can penetrate tissue has proved very challenging.
For their study the researchers developed a new type of nanoparticle that can absorb energy from tissue-penetrating light.
The nanoparticles are made of silica and have thousands of tiny pores in which they carry the chemotherapy drugs. To stop the drugs leaking out, the ends of the pores are capped with nanovalves, like corks in bottles.
It is the nanovalves that respond to the light trigger. They contain special molecules that react when exposed to two-photon light, causing the valves to open and release their drug cargo. Two-photon light is a laser technique that excites electrons into different states, which in turn can change the properties of any compounds they form part of.
The researchers successfully tested their nanoscale drug-carrier and its trigger on lab-cultured human breast cancer cells. Because the light trigger only works up to a range of 4 cm of tissue, the technique is limited to tumors that are not far from the skin surface, such as breast, colon, ovarian and stomach tumors.
The nanoparticles are fluorescent, so their progress in the body can be followed using molecular imaging techniques and researchers can see exactly where the nanoparticle is before activating drug release.
The research team also included members from French research centers, including Jean-Olivier Durand from the University of Montpellier, who was instrumental in developing the new nanoparticle.
Funds from the National Institutes of Health and the French American Cultural Exchange – Partner University Fund (FACE-PUF) helped finance the study.
In April 2012, Medical News Today reported on research into nano factories that could produce drugs at tumor sites. The nano-factories in that study could be activated by UV light to produce protein-based drugs right next to tumors. Cancer-figthing protein-based drugs exist, but they are limited by the fact the body breaks them down before they can reach their target.