Graphite/Aluminum oxide/polylactic acid composite material: A valuable strategy for additively manufacturing cheap and improved electrochemical platforms for sensing sulfamethoxazole in honey samples

Abstract

Composite materials with properties aimed at the additive manufacturing of affordable electrochemical sensors have received special attention in the scientific scenario. For this reason, we proposed a new composite material based on alumina oxide (Al2O3) and graphite (Gpt) dispersed in polylactic acid (PLA) biopolymer. Various proportions between the materials were studied, and a better compromise between printability and electrochemical performance was obtained using Gpt/Al2O3/PLA (30:10:60% w/w). The electrodes were manufactured using a 3D pen, a portable, user-friendly, and low-cost tool. Characterizations by Raman and infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy indicated that Gpt and Al2O3 were successfully incorporated into the PLA matrix. Preliminary studies using species with well-known electrochemical behavior revealed that Al2O3 positively impacts the electrochemical response of the sensor. As a proof of concept, sulfamethoxazole (SMZ), a low-cost antibiotic widely used in beekeeping practices, was selected as the target analyte, and a simple, fast, and selective method using square wave voltammetry was proposed. Using the 3D-printed Gpt/Al2O3/PLA electrode, a wider linear range (2.0 to 40.0 μmol L−1), a 6.5-fold increase in sensitivity, limits of detection (LOD = 0.4 μmol L−1) and quantification (LOQ = 1.2 μmol L−1) were achieved compared to the Al2O3-free electrode (Gpt/PLA). In addition, the proposed sensor was selective against other antibiotics commonly used in beekeeping practices. Three honey samples were analyzed after simple dilution in 0.12 mol L−1 Britton-Robinson buffer, pH 7.0 (background electrolyte), and recoveries close to 100% as well as statistically comparable results from chromatographic analysis certified the accuracy and reliability of the analysis. The proposed approach is innovative and valuable in contributing to the advancement of additive manufacturing in electrochemical sensing, especially in the on-site analysis of antibiotic species in food, a public health challenge.