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The rise of “fast fashion” has driven up the production of low-cost, short-lived clothing, significantly increasing global textile fiber production and, consequently, exacerbating environmental pollution. This study investigated the ecotoxicological effects of different types of anthropogenic microfibers—cotton, polyester, and mixed fibers (50% cotton: 50% polyester)—on marine organisms, specifically sea urchin embryos. All tested fibers exhibited toxicity, with cotton fibers causing notable effects on embryonic development even at environmentally relevant concentrations. The research also simulated a scenario where microfibers were immersed in seawater for 30 days to assess changes in toxicity over time. The results showed that the toxicity of microfibers increased with both concentration and exposure duration, with polyester being the most toxic among the fibers tested. Although synthetic fibers have been the primary focus of previous research, this study highlights that natural fibers like cotton, which are often overlooked, can also be toxic due to the presence of harmful additives. These natural fibers, despite decomposing faster than synthetic ones, can persist in aquatic environments for extended periods. The findings underline the critical need for further research on both natural and synthetic microfibers to understand their environmental impact and potential threats to marine ecosystems and sea urchin populations.

Screen-printed electrodes (SPEs) were produced using conductive inks based on hybrids of polyaniline (PAni) and reduced graphene oxide (rGO). Cyclic voltammetry (CV) showed peaks characteristic of the PAni redox behavior in acidic media for all the modified SPEs. Electrochemical impedance spectroscopy (EIS) showed a significant decrease in the charge-transfer resistances, from 930 Ω for SPE/G:PAni to 544 Ω for SPE/G:PAni-rGO1 and to 303 Ω for SPE/G:PAni-rGO2 with just 0.06% and 0.12% in mass of rGO, respectively, in the final mass composition of the conductive inks. The SPEs were evaluated in the determination of progesterone (P4) hormone in neutral medium (phosphate buffer solution, pH 7.0). The CV results showed higher current signals at SPE/G:PAni-rGO1 compared with SPE/G and SPE/G:PAni, indicating a synergistic effect of PAni-rGO1 in the determination of P4. EIS also showed significant changes in the electrochemical double-layer capacitances in the presence of P4. The limits of detection (LOD) and quantification (LOQ) were, respectively, 211 nmol l ^−1 and 703 nmol l ^−1 . This method is a simple, scalable and low-cost alternative for the fabrication of electrodes based on PAni-rGO hybrids, with synergic properties, aiming for future applications in sensors.