Gloria dos Santos

Carbon-based nanomaterials, particularly multi-walled carbon nanotubes (MWCNTs), are widely used in electrochemical sensors due to their high conductivity and large surface area. However, their poor dispersion often requires synthetic surfactants. Biopolymers such as cellulose have emerged as promising sustainable dispersing agents. In this context, bacterial nanocellulose (BNC) produced from waste offers a green alternative with potential to stabilize and disperse MWCNTs in aqueous media. Herein, a surfactant-free nanocomposite based on BNC produced from beer waste and MWCNTs modified with silver nanoparticles (AgNPs) was engineered to modify electrochemical sensors for pharmaceutical detection of furosemide. The morphology, composition, and electrochemical properties of the nanocomposite were characterized by scanning electron microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV). Furosemide oxidation was evaluated in aqueous medium and synthetic urine using a glassy carbon electrode modified with the MWCNTs/BNC-AgNPs film, and voltammetric parameters were optimized to enhance the analytical response. The sensor presented a linear range from 5.0 to 65.0 µmol L⁻¹, with limits of detection and quantification of 0.19 and 0.64 µmol L⁻¹, respectively. These findings demonstrate the high sensitivity and practical applicability of the MWCNTs/BNC-AgNPs-modified electrode for reliable furosemide determination in urine samples.