Cell stretcher detects cancer

17 Jun 2002

A laser trap that stretches cells can identify differences between healthy and cancerous tissue.

An optical stretcher capable of detecting cancerous cells by measuring how much they stretch has been developed by two researchers at the University of Texas, Austin, US. Jochen Guck and Josef Käs claim that their device can make a distinction between healthy, early-stage and advanced-stage cancerous cells. (Biophys J 81 767).

Guck said: "We think that we have a very powerful technology at hand that a lot of people could benefit from."

He and Käs have developed an optical trapping set-up where two laser beams propagate towards each other and contain the cell in the center of the overlapping beams. The so-called "surface forces" that this generates pull on either side of the cell and stretch it. The researchers have found that cancer cells stretch about twice as much as normal cells.

The stretcher is based on an argon-ion pumped titanium:sapphire laser operating at 780nm. "The wavelength is important. Most visible lasers would simply destroy (opticute) the cell, but the 780 nm wavelength works well," commented Guck. "At this wavelength, nearly all of the laser light is transmitted through the cell."

Cell stretch is imaged in real time using a CCD camera. The stretching is measured along the laser axis as well as in the perpendicular direction to measure how much the cell contracts.

The laser beam is coupled into a singlemode fiber, which in turn is split into three branches. "Two fibers each carry 49% of the total power and are used for trapping and stretching. The other fiber carries 2% of the total light power and is used to monitor the light power in the setup," explained Guck.

Several types of cells have been contained and stretched using the trap. The setup trapped red blood cells using approximately 10mW and stretched them by up to 80% with about 500mW in each beam. Higher powers can stretch cells that have more internal structure.

As yet, the device is not being used in clinical trials, although collaborations have started. Guck and Käs plan to study cervical cells first to detect both the presence of cancer and its stage of advancement using the optical stretcher.

This technology has been patented and licensed to local biotech company Evacyte which is developing the device. The company plans to have a clinical device for early cancer diagnosis on the market within 5 years.