A team of researchers at the University of California Los Angeles (UCLA) have developed an optical sensor that could be used to test saliva for diseases in the body.
The optical sensor can be integrated into a specially designed lab-on-a-chip, or microchip assay, and preprogrammed to bind a specific protein of interest, generating a sustained fluorescent signal as the molecules attach.
A microscope then reads the intensity of the fluorescent light – a measure of the protein’s cumulative concentration in the saliva sample – and scientists gauge whether it corresponds with levels linked to disease.
In their initial experiments, the researchers, led by UCLA’s Dr Chih-Ming Ho, primed the optical protein sensor to detect the IL-8 protein, which at higher-than-normal concentration in saliva is linked to oral cancer.
Using saliva samples from 20 people – half healthy, the others diagnosed with oral cancer – the sensor correctly distinguished in all cases between health and disease.
Importantly, the sensor achieved a limit of detection for IL-8 that is roughly 100 times more sensitive than today’s blood-based Enzyme-Linked ImmunoSorbent Assay (ELISA) tests, the standard technique used to measure protein in bodily fluid.
The limit of detection refers to the ability of the sensor to distinguish the lowest concentration of a protein or other target molecule apart from competing background signals.
Proof-of-principle tests of the sensor took between 30 minutes to an hour to complete. But the figure is somewhat misleading say the researchers, since about 90 per cent of that time was spent preparing the sample, not actually performing the assay. With further work, they believe that the time could be reduced significantly.