Spit Sensor Spots Oral Cancer

Because saliva has a lower concentration of proteins than blood does, the team needed a highly sensitive method to detect the tagged proteins among the background noise, stray molecules in saliva that also fluoresce. So the researchers used a confocal microscope--an imaging system that employs a laser to collect the light generated from a sample--to analyze the saliva. Ho and his team found that focusing the laser light on a specific part of the sample resulted in a lower signal-to-noise ratio, allowing them to detect lower concentrations of the cancer biomarker.

Indeed, Ho says, the device is 100 times more sensitive than the standard protein-detection technique, ELISA. A more extensive and invasive process, ELISA requires that the proteins be purified from the blood before testing.

"The confocal microscope is a sophisticated imaging system at the heart of the UCLA researchers' work and what ultimately led to the improvement in detection," says John McDevitt, a professor of chemistry at the University of Texas, who is also working in salivary diagnostics. The main challenge now facing the UCLA group is how to use this technique outside a laboratory setting, he says.

The UCLA researchers tested the optical protein sensor on 40 patients--20 healthy subjects and 20 individuals with oral cancer. The results proved 95 percent accurate, says Ho. The study was published online in the international journal Biosensors and Bioelectronics.

"The new sensor is a major step in salivary diagnostics, an area that is being looked at very carefully to see where it might be better to use saliva than blood," says Spencer Redding, chair of the department of dental diagnostic science at the University of Texas Health Science Center, in San Antonio, who is working with McDevitt. Other possible applications of such technology include detection of heart disease, infectious disease, and asthma, Redding says.