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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 (Al 2 O 3) 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/Al 2 O 3 /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 Al 2 O 3 were successfully incorporated into the PLA matrix. Preliminary studies using species with well-known electrochemical behavior revealed that Al 2 O 3 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/Al 2 O 3 /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 Al 2 O 3 -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. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new carbon-composite material is proposed for the production of affordable sensors. • Carbon nitride provided electrocatalytic properties for the detection of amaranth. • Amaranth is determined for the first time using a 3D-printed electrochemical platform. • The proposed method can be applied to different food samples. • Results similar to those of UV–Vis spectrometry confirmed the method's accuracy. The production of sustainable materials with properties aimed at the additive manufacturing of electrochemical sensors has gained prestige in the scientific scenario. Here, a novel lab-made composite material using graphite (G) and carbon nitride (C 3 N 4) embedded into polylactic acid (PLA) biopolymer is proposed to produce 3D-printed electrodes. PLA offers printability and mechanical stability in this composition, while G and C 3 N 4 provide electrical properties and electrocatalytic sites, respectively. Characterizations by Raman and infrared spectroscopies and Energy Dispersive X-rays indicated that the G/C 3 N 4 /PLA composite was successfully obtained, while electron microscopy images revealed non-homogeneous rough surfaces. Better electrochemical properties were achieved when the G/C 3 N 4 /PLA proportion (35:5:60) was used. As a proof of concept, amaranth (AMR), a synthetic dye, was selected as an analyte, and a fast method using square wave voltammetry was developed. Utilizing the 3D-printed G/C 3 N 4 /PLA electrode, a more comprehensive linear range (0.2 to 4.2 μmol/L), a 5-fold increase in sensitivity (9.83 μmol−1 L μA), and better limits of detection (LOD = 0.06 μmol/L) and quantification (LOQ = 0.18 μmol/L) were achieved compared to the G/PLA electrode. Samples of jelly, popsicles, isotonic drinks, and food flavoring samples were analyzed, and similar results to those obtained by UV–vis spectrometry confirmed the method's reliability. Therefore, the described sensor is a simple, cost-effective alternative for assessing AMR in routine food analysis. [ABSTRACT FROM AUTHOR]