Development of titanium dioxide based electrochemical sensor for detection of vitreous humor cystine level to estimate postmortem interval

This study presents the development of a novel titanium dioxide (TiO₂)-based electrochemical sensor for the detection of cystine levels in vitreous humor to estimate the postmortem interval (PMI). TiO₂ nanoparticles (NPs) were synthesized via a NaOH-mediated hydrothermal method and characterized using SEM, FTIR, XRD, and DLS. The synthesized NPs exhibited a narrow size distribution (50–150 nm) and high crystallinity. These NPs were drop-cast onto a glassy carbon electrode (GCE) and electrochemical performance was assessed using cyclic voltammetry (CV). The sensor demonstrated a clear redox response with anodic and cathodic peaks centered around +0.46 V and -0.25 V, respectively. A strong linear correlation (R 2 = 0.993) was observed between peak current (13-39 µA) and cystine concentration (0.001-1 mM), with a limit of detection of 0.003 µM. The sensor retained approximately 56% of its initial signal after four weeks of ambient storage. Real sample testing confirmed the sensor's practical application in forensic PMI estimation. This work introduces a rapid, cost-effective, and reliable tool for forensic investigations. Graphical Abstract Schematic illustration of the hydrothermal synthesis of TiO₂ nanoparticles and their modification onto a glassy carbon electrode (GCE) for electrochemical detection of cystine in vitreous humor samples for postmortem interval (PMI) estimation.