Lasers Could Speed Cancer Testing
PHILADELPHIA, Feb. 18, 2010 – When a tissue biopsy is sent to a lab to be analyzed for cancer, it can take hours, days or even a week to get the results. Now, a new analysis technology developed by researchers in Temple University’s Center for Advanced Photonics Research (CAPR) possibly could tell whether tissue is cancerous or normal in a matter of seconds.
“If you get cancer, the diseased tissue changes chemical composition,” said Robert Levis, chairman of chemistry and director of CAPR. “If we can measure the tissue’s chemical composition, we can tell if it’s healthy tissue or abnormal.”
(Image: Joseph V. Labolito / Temple University)
Levis and his group have pioneered a method in which an ultrafast laser is used to vaporize materials, molecules or tissues. Once in gas form, an electrospray mass spectrometer weighs the materials’ biomolecules.
Vaporizing a sample on a plate with the femtosecond (one-quadrillionth of a second) laser releases the molecules into the air, regardless of size or vapor pressure. The molecules are engulfed by the electrospray, much as a hose spray can engulf a flower petal. The electrospray is a water methanol solution ejected from a hypodermic needle by a high voltage, ultimately placing a charge on the molecules. A small capillary tube opposite the needle charged at –5000 V pulls the tiny positively charged droplets into a vacuum and then into the mass spectrometer.
“It’s basically the same way they paint cars,” Levis said. “The droplets come out of the needle, they get charged, and then they’re drawn to the five kilovolts, making a beautiful even coating when you paint or a soft ionization method for mass spectrometry.
“In our experiment, the charged molecule is flung down an evacuated tube, which is about a meter long, and we count the amount of time required to strike a charge detector,” added Levis, a pioneer in strong field chemistry. “The transit time reveals how massive these molecules are, and what’s really amazing is we can analyze molecules as big as Mother Nature makes them.”
So far, Levis’ group has examined biological molecules such as vitamin B12 and oxycodone before moving to leaves and plants as well as complex biological mixtures such as blood. Graduate students John Brady and Elizabeth Judge directed the laser to different parts of an impatiens plant and saw different mass-spectral signatures for the stem, leaves and petals.
“We even put a spot of blood down on the slide, vaporized it with the laser and the electrospray and, amazingly, we were able to see all of the hemoglobins in the mass spectrometer,” Levis said. “So we can differentiate tissue types. So now, I think we will be able to use this method to tell the difference between cancer tissue and normal tissue. If we can build a library of tissue signatures, we will be able to tell quickly exactly what certain type tissue is because our mass spectra are measured in real time.”
The researchers have published their initial findings in the journal Rapid Communications in Mass Spectrometry.
Levis said the researchers now are looking to collaborate with other researchers on liver and lung disease.
For more information, visit: www.temple.edu
- mass spectrometer
- A device used to measure the masses and relative concentrations of atoms and molecules. It utilizes the Lorentz force generated by external magnetic field on a moving charged particle, in which the particles are deflected by the magnetic field according to their masses. Once deflected, the particles are detected and recorded electrically to provide a mass spectrum of the input beam of ions.
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