Real-Time Detection of Toxic Metal Ions: Innovations in Electrochemical Sensing for Future Medical Applications

Heavy metal toxicity in humans is a major concern, affecting vital organs like the kidneys and liver and disrupting neurotransmission, which can lead to neurodegenerative diseases. While there are tools to detect metals in aqueous solutions, few studies have focused on detecting toxic metal ions in vivo due to poor temporal resolution and the need for pretreatment. In this study, we developed sensors using two electrochemical methods to detect toxic metal ions in complex matrices such as artificial cerebrospinal fluid, blood, and urine. Our glass nanopipets are based on ion transfer between immiscible electrolyte solutions, and our carbon fiber microelectrodes (CFMs) use adsorption-driven redox chemistry of metal ions. We demonstrate for the first time the detection of Cd2+ ions in artificial urine and blood using 600 nm diameter glass pipets. Additionally, we calculate the binding constants of EDTA, a chelating agent, with Cd2+. We also enhance metal detection by modifying single-bore CFMs and developing double-bore and four-bore CFMs. These can detect both toxic metal ions and neurotransmitters using fast-scan cyclic voltammetry with millisecond temporal resolution. Our sensors exhibit excellent sensitivity, selectivity, and stability, showcasing their potential for future in vivo applications. This advancement paves the way for real-time monitoring of metal ion levels in biological systems, contributing significantly to medical diagnostics and treatment of metal toxicity. Our work emphasizes the importance of advanced electrochemical sensors for in vivo detection of toxic metal ions. By improving temporal resolution and eliminating extensive pretreatment, these sensors provide real-time, accurate measurements of metal ion concentrations in biological fluids. This capability is crucial for early diagnosis and effective treatment of heavy metal poisoning, ultimately improving patient outcomes.