Low-cost electrochemical sensor for ciprofloxacin antibiotic based on green-synthesized silver nanoparticles and carbon black

An unprecedented electrochemical sensor based on low-cost films combining carbon black (CB) and green-synthesized silver nanoparticles (AgNPs) is proposed for the voltammetric determination of ciprofloxacin, an antibiotic widely used in the treatment of infectious diseases. AgNPs were biosynthesized by using an aqueous plant extract of Camellia sinensis (black tea) in which the metabolites worked as reducing and stabilizing agents. The AgNPs and CB nanoparticles were incorporated within a crosslinked chitosan (Ch) film over the surface of a glassy carbon electrode (GCE). The nanomaterials were characterized by scanning electron microscopy (SEM), ultraviolet–visible molecular absorption spectrophotometry (UV–Vis), dynamic light scattering (DLS), zeta potential, and cyclic voltammetry (CV). The sensor modified with both nanomaterials (AgNPs-CB-Ch/GCE) showed a significatively enhanced analytical signal for the ciprofloxacin irreversible oxidation peak. Using square-wave voltammetry (SWV) under the optimized working conditions and the proposed AgNPs-CB-Ch/GCE sensor, the analytical curve displayed two linear concentration ranges of 3.1 to 24.8 µmol L⁻¹ and of 36.9 to 130.3 µmol L⁻¹, with a limit of detection of 0.48 µmol L⁻¹. The proposed electrochemical sensor presented good precision as shown from repeatability tests, as well as it was successfully applied in the quantification of ciprofloxacin in the synthetic urine sample, with recovery results close to 100% for both linear concentration ranges. The presented AgNPs synthetic method and CIP electrochemical detection are found to be simple and efficient compared to the conventional methods commonly reported.