JNCASR: Electrochemical sensor detects dopamine, paracetamol

Sebastian Peter (right) and Rajamani have developed a nanocomposite that efficiently detects dopamine and paracetamol.  

Developing electrochemical sensors to detect dopamine and paracetamol in the body is an active field of research. A team from Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru, has come up with a nanocomposite material made of platinum-doped cerium oxide and cuprous oxide that works efficientlyin electrochemical cells to detect their levels, in combination, in spiked human urine and serum samples.

Neurotransmitters transmit signals from one neuron to another; dopamine is one such which is responsible for reward-motivational behaviour, among other things. When not present in the right amount, it can lead to, for example, Parkinson’s disease. Paracetamol is a drug commonly used to treat pain and fevers; however, if present above a critical concentration, this can affect the sympathetic nervous system. Dopamine levels have been known to be affected by long-term use of paracetamol. Thus, it is useful to know the levels of these two chemicals in the body simultaneously.

To detect the concentration of an analyte, electrochemical methods measure the potential and current in an electrochemical cell containing the analyte. In this case, the analytes to be detected are dopamine and paracetamol. The electrochemical cell used by the researchers had three electrodes: the working electrode consisting of the nanocomposite material (platinum doped cerium oxide and cuprous oxide); the counter electrode (platinum wire) and reference electrode (silver-silver chloride) explains Sebastian C Peter, of JNCASR, in whose lab the experiments were done.

The need for the electrodes made of nanocomposite arises because, if instead, a bare electrode were used, several problems could arise, such as a low potential gap between analytes and interference with other biomolecules, to mention just two. Therefore, the researchers modified the surface of the electrode with the given nanocomposite material. “Chemically modified electrodes are highly preferred due to their large surface area, reversible redox activity, high surface oxygen mobility, chemical inertness, bio-compatibility, non-toxicity and applicability over a wide range of areas,” says Dr Peter. The work is to be published in ACS Applied Nano Materials.

In recent times, the use of cerium oxide–doped graphene nanocomposites has been in vogue. This is mainly due to the electrochemical properties of cerium oxide. The cerium oxide nanoparticles have dual oxidation states of cerium and this delivers catalytic properties, leading to their action as a radical scavenger on the surface. This facilitates oxidation of dopamine and paracetamol. In this, the researchers innovated by adding platinum to the nanocomposite. “Introducing platinum has great significance due to the high electrocatalytic activity, outstanding conductivity, adsorption capabilities and biocompatibility in electrochemical sensors,” Dr Peter adds.

While in its bare form, cuprous oxide, too, has good electrocatalytic activity towards oxidation of biomolecules, its use is limited by its dispersion on the unmodified electrodes.

“The peak potential of dopamine and paracetamol is fixed at 160 mV and 360 mV, respectively. Peak current increases linearly with concentration of dopamine and paracetamol,” Dr Peter explains.

The performance of electrode using platinum doped cerium oxide and cuprous oxide is better than the cerium oxide–graphene material, as found by the researchers.

Next, the team is going to target multiple biomolecule detection using the nanocomposite and to get into real-time device fabrication.