Biosensors stand out as one of the greatest scientific advances in recent decades, as they enable rapid testing for numerous analytes, whether crucial for clinical diagnostics or in determining environmental contaminants. Peroxidase is one of the most widely used enzymes in amperometric biosensor research. Therefore, it is increasingly important to advance our knowledge of the applications of this enzyme and explore alternative sources to commercial peroxidase (HRP) from Armoracia rusticana. In this study, plants were investigated as sources of peroxidase, with the extract from gherkin (Cucumis anguria) exhibiting the highest activity. It was selected and used as the source of this enzyme for immobilization on titanate nanotubes (NTT) and iron oxide magnetic nanoparticles (NPM) for the development of modified carbon paste biosensors (NTTP and NPMP). In the second part of the thesis, other biosensors were prepared using filtered and concentrated gherkin extract (NTTP-F and NTTP-R) and one with commercial peroxidase (NTT-HRP). The constructed biosensors were employed in the quantification of dopamine in a pharmaceutical product (5.00 mg mL-1) using square wave voltammetry (SWV). The application of a potential of -0.30 V for 5 s was necessary before each SWV scan to promote the desorption of the analyte from the biosensor surface. Parameters such as pH, amplitude, and frequency were optimized. For the NTTP biosensor, the obtained calibration curve ranged from 4.98 to 65.4 μmol L-1, with a detection limit (LD) of 2.46 μmol L-1. The NPMP biosensor calibration curve ranged from 4.98 to 61.0 μmol L-1, with an LD of 2.11 μmol L-1. In the determination of dopamine in the commercial ampoule, the NTTP biosensor presented a confidence interval of 5.04 ± 0.06 mg mL-1 (RE = +1.2%), and the NPMP biosensor showed 4.76 ± 0.04 mg mL-1 (RE = -4.8%). The NTT biosensor demonstrated superior results compared to the NPM biosensor in terms of a higher signal, better repeatability, a slightly broader calibration curve, and greater accuracy in the standard addition experiment. NTTP-R, NTTP-F, and NTT-HRP biosensors exhibited the same linear range of the calibration curve (4.98 to 56.6 μmol L-1), with LDs of 1.20, 1.04, and 1.83 μmol L-1, respectively. In the determination of dopamine in the commercial ampoule, NTTP-F presented a confidence interval of 5.47 ± 0.09 mg mL-1 (RE = +10%), NTTP-R showed 5.0 ± 0.2 mg mL-1 (RE = 0%), and NTT-HRP displayed 5.0 ± 0.4 mg mL-1 (RE = 0%). In the interference test with 10 g L-1 urea, the NTTP-R biosensor exhibited the least signal loss. Finally, the NTTs displayed better electrochemical characteristics than the NPMs. Despite being quite similar, the NTTP-R biosensor yielded better results than NTTP-F and the NTT-HRP biosensor. Biosensors constructed with gherkin extract did not show significant differences from the biosensor constructed with HRP. However, the NTTP-R biosensor exhibited better characteristics than both the NTT-HRP and the NTTP-F.