Lab on a Syringe: Strategic Design of 1T SnS₂/MXene Embedded Single-Stranded Carbon Yarn for Real-Time Stress Biomarker Detection

An electrochemical sensor was developed in this study by utilizing a 1T SnS2–Nb2CTx heterostructure nanocomposite modified carbon yarn (CY) electrode for detecting serotonin (5-HT) in human biofluids. Utilizing the enhanced electrochemical activity of the 1T phase of SnS2, a nanocomposite was made with Nb2CTx MXene via a hydrothermal method. The nanohexagon architecture of SnS2 provides a heterojunction with Nb2CTx MXene and enables a conductive electron transfer network, leading to improved sensing capabilities with an enhanced electrochemical response. A detailed study was conducted to elucidate the mechanism behind the heterostucture formation with the help of ultraviolet photoelectron spectroscopy (UPS) analysis. The 1T SnS2–Nb2CTx nanocomposite provided effective active sites for enhancing its electrochemical performance by the presence of terraces and edges in the hexagonal structured 1T SnS2 and by the inherent electrochemical property of Nb2CTx MXene. The fabricated 1T SnS2–Nb2CTx nanocomposite based electrochemical sensor demonstrated a wide linear detection range of 1 to 100 μM for 5-HT, with a detection limit of 81 nM. In addition, the developed sensor demonstrated high selectivity, excellent repeatability, reproducibility, as well as good stability for 5-HT detection. The sensor was beneficially used to determine 5-HT levels in artificial samples of human serum, cerebrospinal fluid (CSF), interstitial fluid (ISF), and human sweat, confirming its practicality for real sample analysis. Finally, a “lab on a syringe” prototype model was developed by placing three thread electrodes on a commonly available syringe barrel, and it demonstrated promising capabilities for POC applications in next-generation healthcare.