Killing cancer cells -- one at a time
A team of U.S. engineers and researchers have developed a laser surgery probe which targets individual cancer cells. This 'microscalpel' can destroy a single cancerous cell while leaving nearby cells intact. According to the lead researcher, 'You can remove a cell with high precision in 3-D without damaging the cells above and below it. And you can see, with the same precision, what you are doing to guide your microsurgery.' This 'microscalpel' is certainly promising, but I have some doubts. As a cancer involves many cells, how would a human operator be able to remove all of them if he can only kill them one by one? And how could he target all these cancerous cells with this laser tool? It would certainly take lots of time. But read more...
You can see above the combined effects of "two-photon microscopy and femtosecond laser microsurgery on a single layer of breast carcinoma cells. (a) Two photon image of a single layer of live breast carcinoma cells after uptake of calcein AM taken prior to irradiation with high intensity pulses. (b) The same FOV [field of view] as (a), immediately after irradiation with a single pulse at 280 nJ pulse energy. Average laser power used for imaging in both images was 10 mW. Both images were averaged over 5 seconds at 10 fps and spatially filtered. Note that the targeted cell has lost fluorescence while the cell touching the targeted cell is left intact. Scale bars are 20 μm." (Credit: Adela Ben-Yakar and colleagues)
This research project has been led by Adela Ben-Yakar, Assistant Professor in the Mechanical Engineering Department of the University of Texas at Austin. She was helped by several members of her research group about femtosecond lasers. She also collaborated with Olav Solgaard, Associate Professor of Electrical Engineering at Stanford University.
Before going further, here is a short description of femtosecond lasers and their medical usages. "Femtosecond lasers produce extremely brief, high-energy light pulses that sear a targeted cell so quickly and accurately the lasers' heat has no time to escape and damage nearby healthy cells. As a result, the medical community envisions the lasers' use for more accurate destruction of many types of unhealthy material. These include small tumors of the vocal cords, cancer cells left behind after the removal of solid tumors, individual cancer cells scattered throughout brain or other tissue and plaque in arteries."
Now, let's look at what did Ben-Yakar and her colleagues. "Ben-Yakar's laboratory has overcome technological challenges to create a microscope system that can deliver femtosecond laser pulses up to 250 microns deep inside tissue. The system includes a tiny, flexible probe that focuses light pulses to a spot size smaller than human cells. [...] Within a few years, Ben-Yakar expects to shrink the probe's 15-millimeter diameter three-fold, so it would match endoscopes used today for laparoscopic surgery. The probe tip she has developed also could be made disposable -- for use operating on people who have infectious diseases or destroying deadly viruses and other biomaterials."
For more information, please read the University of Texas at Austin news release mentioned in the introduction. And please note that this research work has been published by Optics Express under the name "Miniaturized probe for femtosecond laser microsurgery and two-photon imaging" (Vol. 16, Issue 13, Pages 9996-10005, June 23, 2008).
Here is a link to the abstract. "Combined two-photon fluorescence microscopy and femtosecond laser microsurgery has many potential biomedical applications as a powerful 'seek-and-treat' tool. Towards developing such a tool, we demonstrate a miniaturized probe which combines these techniques in a compact housing. The device is 10 x 15 x 40 mm3 in size and uses an aircore photonic crystal fiber to deliver femtosecond laser pulses at 80 MHz repetition rate for imaging and 1 kHz for microsurgery. A fast two-axis microelectromechanical system scanning mirror is driven at resonance to produce Lissajous beam scanning at 10 frames per second. Field of view is 310 µm in diameter and the lateral and axial resolutions are 1.64 μm and 16.4 μm, respectively. Combined imaging and microsurgery is demonstrated using live cancer cells."
From the above link, you can have access to the full article. I'm not including a link, because it is a variable one. Anyway, the above figure and its caption were picked from this article. And before getting to the conclusions of this paper, here are some acronyms used in it: MEMS (microelectromechanical systems), FLMS (femtosecond laser microsurgery), TPM (two-photon microscopy) and NA (numerical aperture).
So what's next? "Future design improvements such as a metallic-coated high reflectivity MEMS mirror and a high-NA miniature objective lens, which will provide increased power delivery and improved collection efficiency, respectively, can enable imaging of cellular autofluorescence with the probe. An increase in numerical aperture will also be beneficial for precise FLMS inside bulk tissue, where tighter focusing can help to reduce the pulse energy and avoid collateral damage arising from nonlinear affects. Meanwhile, novel two-photon contrast agents, such as bright luminescent gold nanorods, can be used to reduce the required excitation power by a couple of orders of magnitude in addition to providing molecularly specific imaging."
The researchers also think that their system might be used for other applications. "Fiber-coupled systems with near-video rate imaging and high precision surgery capabilities such as the one presented here can be used for live animal studies for developing clinical techniques. The optical design approach presented in this paper shows great promise and could find applications in such disparate fields as oncology, dermatology, and neurosurgery."
Sources: The University of Texas at Austin news release, June 23, 2008; and various websites
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