AgNP/MWCNT‐Based Electrochemical Sensor for Sensitive and Simultaneous Detection of Tryptophan and Indole‐2‐Carboxylic Acid

ABSTRACT Chronic kidney disease (CKD) is a progressive condition marked by nephron loss, often leading to end‐stage renal disease (ESRD). Patients with ESRD commonly experience cutaneous complications such as uremic pruritus, linked to the accumulation of uremic solutes. Among these, tryptophan (Trp) and indole‐2‐carboxylic acid (I2CA) are significant biomarkers requiring sensitive detection. This study presents a rapid and precise electrochemical method for the simultaneous quantification of Trp and I2CA in plasma and skin samples from hemodialysis patients. A glassy carbon electrode (GCE) was modified with multiwalled carbon nanotubes (MWCNTs) and AgNO 3 / N , N ‐dimethylformamide, and its properties were characterized using electrochemical impedance spectroscopy and scanning electron microscopy. Differential pulse voltammetry demonstrated linear responses for Trp (0.1–100 µg/mL) and I2CA (0.1–1.1 µg/mL) in a pH 7.0 phosphate buffer solution. The method achieved detection limits of 0.079 µg/mL for Trp and 0.01 µg/mL for I2CA. Recovery rates ranged from 97.6% to 99.6% for Trp and 97.5% to 100.4% for I2CA in patient samples. This electrochemical sensor offers high sensitivity, cost‐effectiveness, and ease of use, making it a promising tool for clinical monitoring of uremic toxins in CKD.