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 SnS 2 –Nb 2 CT x 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 SnS 2, a nanocomposite was made with Nb 2 CT x MXene via a hydrothermal method. The nanohexagon architecture of SnS 2 provides a heterojunction with Nb 2 CT x 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 SnS 2 –Nb 2 CT x nanocomposite provided effective active sites for enhancing its electrochemical performance by the presence of terraces and edges in the hexagonal structured 1T SnS 2 and by the inherent electrochemical property of Nb 2 CT x MXene. The fabricated 1T SnS 2 –Nb 2 CT x 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.