A new metallic nanostructure, developed by researchers from the University of California (Santa Cruz), already shows hope in their experiment to cure cancer and can be used in the future for chemical and biological sensors and in other applications
The hollow gold nanosphere, developed in the laboratory of Jin Zhang, professor of chemistry and biochemistry at UCSC University, has a set of unique characteristics, including: strong, narrow and tunable absorption of light. The researcher works in collaboration with researchers from the University of Texas, who have already used these new nanostructures to direct anti-cancer substances to the tumor sites in the field called "photothermal cancer therapy". They reported good results from preclinical studies they conducted earlier this year and which were published in the journal Clinical Cancer Research.
The lead researcher is scheduled to describe his and his group's research on the hollow gold nanoparticles in a lecture to be given at the annual meeting of the American Chemical Society in Salt Lake City.
"The factors that make this structure a special lacquer are the combination of the spherical shape, the small size and the strong absorption of light in the visible and near-infrared," says the lead researcher. "The intake is not only strong but also narrow and adjustable. All these characteristics are important for the treatment of cancerous tumors.”
The researchers were able to control the preparation of the hollow gold nanoparticles to create particles with consistent optical properties and size. The spheres can be prepared in sizes ranging from 70-20 nanometers in diameter, which is optimal for biological applications that require the introduction of the particles into the interior of living cells. The optical properties can be adjusted by changes in the size of the particle and the thickness of its walls.
In experiments against cancer, led by Chun Li, the researchers attached a short peptide to the nanoparticles that allows the particle to bind to cancer cells. After injecting the nanoparticles into mice with malignant skin cancer (melanoma), the researchers irradiated the tumor areas with near-infrared radiation using a laser while heating the gold nanoparticles and eliminating the cancer cells to which these particles are attached.
Despite this success, the field of cancer treatment was not the first goal of the lead researcher when his laboratory began working several years ago on the topic of preparing and characterizing hollow gold nanoparticles. The group examined a wide variety of metallic nanostructures in order to improve their properties and this for the field of "surface-enhanced Raman scattering" (SERS). It is a powerful optical method used for sensitive detection of biological particles and other applications. One of the researcher's students tried to repeat a work published on this subject by Chinese researchers back in 2005. In the process, he succeeded in perfecting the preparation of the hollow gold nanoparticles and then demonstrated and characterized their activity in SERS.
"In this process, it is possible to produce SERS-active nanoparticles that are significantly smaller than other typical nanoparticle structures used in this field, and can be used as sensing components that are more easily inserted into the interior of cells for local intracellular measurements," explains the researcher.
The collaboration with researcher Li began when Zhang listened to his lecture at a conference on the use of solid nanoparticles for photothermal cancer therapy. Zhang immediately noticed the advantages of his hollow gold nanoparticles for this method. Li uses near-infrared radiation in his process because it provides good tissue penetration. However, the solid gold nanoparticles he used did not absorb radiation in this range effectively. Researcher Zhang told researcher Li that he was able to make hollow gold nanospheres that most effectively absorb radiation at exactly the wavelength emitted by his laser (800 nanometers).
"The local heat that destroys the cancer cells depends on the radiation absorbed by the metallic nanoparticles, so a more efficient absorption of radiation means a more efficient and selective process," explains the lead researcher. "The new hollow gold nanoparticles were fifty times more efficient than the previously used solid gold nanoparticles in absorbing near-infrared radiation."
The research group began to examine other nanostructures that can be prepared by the same method. For example, one of the researchers in the group prepared hollow nanostructures with a double shell consisting of gold and silver, and which displayed improved SERS activity relative to the hollow gold nanoparticles. The ability to tune the optical properties of the new nanospheres makes them versatile, says the researcher. "This is a unique structure that provides clear advantages compared to other nanostructures, so it has great future potential," he adds.
