Gold nanoparticle-based electrode efficiently co-detects dopamine and uric acid in urine samples, shows new study in Journal of Pharmaceutical Analysis

Urinalysis, or the detection and estimation of various pathophysiological substances in urine samples, is routinely recommended by physicians for disease diagnosis. Increased levels of uric acid (UA), for instance, may indicate underlying kidney or heart disease. Similarly, an increase in the urinary levels of dopamine (DA) may indicate the presence of neurological disorders like neuroblastoma or Parkinson’s disease. Because pathology labs need to simultaneously determine the urinary levels of multiple substances, techniques that permit such co-detection are necessary. However, such co-analyses sometimes present with technical hurdles. In the case of urine samples, the relatively higher concentrations of ascorbic acid (AA) in urine interferes with the simultaneous detection of DA and UA, both of which are present at relatively lower levels.

A group of researchers led by Associate Professor Dongdong Zhang of Xi'an Jiaotong University, China, has now been able to overcome this limitation through a novel electroanalytical technique that permits the co-detection of DA and UA in urine samples even in the presence of AA.

In their paper, which was made available online on September 17, 2021 and subsequently published in Volume 11 Issue 6 of the Journal of Pharmaceutical Analysis in December 2021, the researchers describe how they combined a nanocomposite mixture, which had an average grain size of 10^-9 meters or more, made up of gold nanoparticles (AuNPs), a special (conducting) polymer, and electrochemically-treated graphene oxide over a conventional glassy carbon electrode (GCE), to get a superior electrode for use in their technique. A GCE combines the properties of glass with those of graphite. However, it needed to be modified for the selective and simultaneous detection of DA and UA in the presence of high concentrations of AA.

To this end, the researchers employed a combination of chemical and electrochemical methods. They started with poly(3,4-ethylenedioxythiophene), or PEDOT, which is a highly conductive polymer with much promise in the field of biosensors. Explaining the mechanics of their technique, Dr. Zhang says, “PEDOT can be overoxidized to obtain OPEDOT, whose hydrophilicity and unique properties make it useful in electroanalytical applications. However, since OPEDOT is not as good an electrical conductor or catalyst, it is modified with suitable nanomaterials, in this case, gold nanoparticles.”

The PEDOT-AuNPs were chemically synthesized from chloroauric acid and 3,4-ethylenedioxythiophene at room temperature. The addition of graphene oxide (GO) resulted in the formation of a homogeneous suspension of PEDOT-AuNPs-GO. This suspension was then dropped onto the surface of a GCE and dried. Finally, following an electrochemical procedure, the nanomaterial OPEDOT-AuNPs-ERGO/GCE was successfully fabricated and readied for bioanalytical measurements.

When used, the modified electrode was able to simultaneously detect extremely tiny amounts of DA (1 mM) and UA (5 mM) under physiological conditions, even in the presence of a large excess (1.0 mM) of AA. Quite an astounding observation, indeed!

The research team foresees a bright future for this novel nanomaterial-based application, especially in clinical and diagnostic setups. “Our novel, graphene-based, ternary composite, with its advantageous features, is a promising candidate for electroanalytical and clinical applications,” said Dr. Zhang.

Future studies are certainly required, but this novel nanocomposite electrode has strong potential to become the gold standard for diagnostics in pathology laboratories.                   

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Reference
DOI: https://doi.org/10.1016/j.jpha.2021.09.005

About Dr. Dongdong Zhang  
Dr. Dongdong Zhang obtained his Ph.D. in analytical chemistry from Shaanxi Normal University, China. He is an Associate Professor at the School of Pharmacy, Xi'an Jiaotong University. His research, primarily focusing on the development of biosensors, has wide implications in bioanalytical chemistry, molecular diagnosis, nanobiotechnology, functional biosensing, chip analysis, immune health studies, cellular analysis, genetic analysis, and clinical testing. Dr. Zhang has won two Shaanxi Province Higher Education Science and Technology awards and an award of excellence for his doctoral dissertation. He has published over ten articles in the reputed international journals such as Biosensors and Bioelectronics and Electrochimica Acta.