Detection of cancer through simultaneous detection of serotonin and dopamine

Serotonin (5-hydroxytryptamine; 5-HT) is a hormone and a neurotransmitter and it is involved in cognitive activities, central nervous function and mood regulation. The effect of serotonin extends to the immune system, vasculature and the gut. Thus, an abnormal regulation of serotonin secretion can result in pathologies in these areas. Serotonin is also important in the development of the mammary gland and abnormalities in the regulation of serotonin production plays an important role in the development of breast cancer. There is a change in the expression of serotonin receptors observed in breast cancer cells. This contributes to the abnormal cell growth and allows the tumor avoid the tumor suppressive actions of serotonin. It is therefore important to monitor the concentration of serotonin for the early diagnosis and prognosis of breast cancer. In addition, the uptake of dopamine by its transporter is affected by a high level of serotonin making it necessary to develop a dopamine sensor.

Several methods have been developed to detect serotonin and these include enzyme-linked immunosorbent assay (ELISA), HPLC and spectroscopy. Despite their benefits, these methods can only be performed by well-trained professionals and require multistep procedures, pretreatment steps, large amount of sample and expensive instrumentation. These serve as setbacks, which make these methods non-applicable as point-of care test (POCT) methods. However, a much more promising method is the electrochemical detection of serotonin because it is simple, affordable, non-invasive, and has the potential of being used with POC devices. Therefore, it is necessary to develop highly precise and sensitive sensor that can monitor the amount of serotonin released from biological samples such as cancer cells. To this note, scientists at Pusan National University in South Korea: Dr Saeromi Chung, Dr. Mahmood H. Akhtar, A. Benboudiaf, Professor Deog‐Su Park and Professor Yoon‐Bo Shim, developed a new sensor for serotonin and dopamine using AuNPs@rGO/pTBA Pd (C2H4N2S2)2 electrode. They demonstrated the clinical utility of their sensor and that it can be used to monitor serotonin levels in both normal and cancer cells. Their study is published in the Journal Electroanalysis.

The research team fabricated an electrochemical sensor to detect both serotonin and dopamine in human plasma samples and breast cancer cells, based on the conducting polymer composite with a palladium complex (Pd (C2H4N2S2)2). The sensor was developed by using the Pd(C2H4N2S2)2 complex-anchored poly2,2:5,2-terthiophene-3-(p-benzoic acid) (pTBA) layer on the AuNPs decorated reduced graphene oxide (AuNPs@rGO) substrate. They observed that the dynamic ranges was from 0.1 to 200 μM, for dopamine and from 0.02 to 200 μM for serotonin and the detection limits were 24.0 nM and 2.5 nM (RSD <4.20, 3.78%), respectively.

The authors successfully confirmed that the amount of serotonin released from breast cancer cells is 3.1 times higher than the normal cells. Serotonin concentration was found to be 135.2 nM in normal cells and 411.7 nM in cancer cells. The recovery ratios were in the range from 95.2-104.0% for dopamine and from 97.2-103.8% for serotonin. The recovery tests proved that the sensor was accurate and could be used in clinical settings.

In summary, the Pusan National University researchers have developed an innovative sensor that is simple, precise and can detect simultaneously dopamine and serotonin in biological samples. This will be useful in the management of breast cancer.