An iron(iii) oxide-anchored conductive polymer–graphene ternary nanocomposite decorated disposable paper electrode for non-enzymatic detection of serotonin

Abstract

Serotonin, also known as 5-hydroxytryptamine (5-HT), is an important neurotransmitter that regulates many physiological processes. Both low and high concentrations of 5-HT in the body are associated with several neurological disorders. Hence, there is an urgent need to develop fast, accurate, reliable, and cost-effective disposable sensors for 5-HT detection. Herein, we report the sensing of 5-HT using a disposable paper-based electrode (PPE) modified with a ternary nanocomposite comprising poly(pyrrole) (P(py)), reduced graphene oxide (rGO), and iron oxide (Fe₂O₃). The sensor material was well characterized in terms of its structural, morphological, and chemical attributes using electron microscopy, spectral techniques, and electrochemical studies to prove the robust formation of the electroactive ternary nanocomposite and its suitability for 5-HT detection. The developed sensor exhibited an impressive limit of detection (LOD) of 22 nM with a wide linear range of 0.01 to 500 μM, which falls in the recommended clinically relevant range. The analytical recovery, spike sample analysis, and interference studies with ascorbic acid (AA), uric acid (UA), and epinephrine (E) showed satisfactory results, wherein the sensor could detect simultaneously both 5-HT and dopamine (DA). The potential practical utility of the developed sensor was further assessed by quantifying the concentration of 5-HT in the brain samples of Drosophila melanogaster, a versatile genetic model organism employed for modeling different neural disorders in humans, and validated by gold-standard HPLC-UV experiments. The as-fabricated single-run disposable sensor with a ternary nanocomposite exhibits excellent stability with good reproducibility and is a promising platform for identifying clinically relevant concentrations of 5-HT.