Rice-Spikelet-like Copper Oxide Decorated with Platinum Stranded in the CNT Network for Electrochemical In Vitro Detection of Serotonin

Abstract

The specific monitoring of serotonin (ST) has provoked massive interest in therapeutic and biological science since it has been recognized as the third most significant endogenous gastrointestinal neurotransmitter. Hence, there is a great need to develop a sensitive and low-cost sensing platform for the detection of a clinically relevant ST level in biological matrices. Herein, we develop a simple two-step approach for an ultrasensitive electrochemical (EC) sensor with the Cu₂O metal oxide (MO)-incorporated CNT core that has been further deposited with a transitional amount of platinum nanoparticles (Pt NPs). We presented, for the first time, the deposition of Pt NPs on the (CNTs-Cu₂O-CuO) nanopetal composite via the galvanic replacement method, where copper not only acts as a reductant but a sacrificial template as well. The electrocatalytic aptitude of the fabricated EC sensing platform has been assessed for the sensitive detection of ST as a proficient biomarker in early disease diagnostics. The synergy of improved active surface area, remarkable conductivity, polarization effect induced by Pt NPs on CNTs-Cu₂O-CuO nanopetals, fast electron transfer, and mixed-valence states of copper boost up the redox processes at the electrode-analyte junction. The CNTs-Cu₂O-CuO@Pt-modified electrode has unveiled outstanding electrocatalytic capabilities toward ST oxidation in terms of a low detection limit of 3 nM (S/N = 3), wide linear concentration range, reproducibility, and incredible durability. Owing to the amazing proficiency, the proposed EC sensor based on the CNTs-Cu₂O-CuO@Pt heterostructure has been applied for ST detection in biotic fluids and real-time tracking of ST efflux released from various cell lines as early disease diagnostic approaches.

Keywords: CNTs; cell line; copper oxide; electrochemical sensor; galvanic replacement; serotonin.