doi:10.1038/nindia.2013.106 Published online 12 August 2013
Researchers have devised a new type of sensor that is capable of detecting minute traces of ascorbic acid (vitamin C) and dopamine, a neurotransmitter present in the brain and other organs . Depleted dopamine levels lead to neurodegenerative diseases such as Parkinson's disease. This sensor is expected to be very effective for diagnosing Parkinson's disease through monitoring dopamine levels and also for measuring ascorbic acid levels in biological samples.
Conventional sensors are fabricated by imprinting molecules of a single kind of polymer on an electrode surface. However, such single-polymer sensors are incapable of separating and detecting multiple compounds that are often present in samples such as multicomponent drugs, foodstuffs and agricultural products containing organophosphate pesticides.
The researchers overcame this obstacle by developing a sensor consisting of a polymer film dispersed with multiwalled carbon nanotubes. This film is imprinted with two kinds of molecules (ascorbic acid and dopamine), and was used to produce a carbon ceramic electrode.
To determine the efficacy of this sensor, the researchers carried out electrochemical studies using laboratory-based human-derived blood samples and cerebrospinal fluid samples that contained ascorbic acid and dopamine. The peak current was found to increase with increasing dopamine concentration; it also increased with increasing ascorbic acid concentration, although at a slower rate. The detection limit of the sensor for dopamine was almost ten times higher than that for ascorbic acid, for both independent and simultaneous measurements in aqueous and solid samples.
"This sensor is a promising biomedical tool for detecting biomarkers such as ascorbic acid and dopamine in various chronic diseases in a clinical set-up," says Bhim Bali Prasad, a co-author of the study.