{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T11:16:13Z","timestamp":1788434173845,"version":"build-2803163510"},"reference-count":48,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,29]],"date-time":"2026-08-29T00:00:00Z","timestamp":1787961600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>A horseradish peroxidase (HRP)-based electrochemical biosensor was developed for melatonin (MLT) detection using a graphene-modified screen-printed electrode (G\/SPE). HRP was immobilized at different temperatures (4 \u00b0C and 20 \u00b0C) and enzyme amounts (10 and 20 \u00b5L of 5 mg\/mL HRP solution) to optimize the performance of the biosensors. FTIR analysis confirmed successful enzyme immobilization, while differential pulse voltammetry (DPV) showed a clear oxidation peak of MLT at 1.1 V with enhanced current responses for HRP-modified electrodes. The optimal biosensor, prepared at 4 \u00b0C with 10 \u00b5L enzyme of 5 mg\/mL HRP solution, exhibited the best analytical performance, with a linear range of 0.4\u20133.6 \u00b5M, and a detection limit of 1.02 \u00b5M. Kinetic studies confirmed strong enzyme-substrate affinity, while the biosensors demonstrated excellent repeatability and a good stability. The method was successfully validated on pharmaceutical products, proving to be a reliable and an accurate tool for MLT quantification in real samples.<\/jats:p>","DOI":"10.3390\/bios16090475","type":"journal-article","created":{"date-parts":[[2026,8,31]],"date-time":"2026-08-31T05:55:56Z","timestamp":1788155756000},"page":"475","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Development of a Horseradish Peroxidase-Based Electrochemical Biosensor for Melatonin Detection"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-3473-3500","authenticated-orcid":false,"given":"Andra-Georgiana","family":"Trifan","sequence":"first","affiliation":[{"name":"Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, \u2018Dunarea de Jos\u2019 University of Galati, 47 Domneasca Street, 800008 Galati, Romania"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3823-4174","authenticated-orcid":false,"given":"Constantin","family":"Apetrei","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Physics and Environment, Faculty of Sciences and Environment, \u2018Dunarea de Jos\u2019 University of Galati, 47 Domneasca Street, 800008 Galati, Romania"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e12961","DOI":"10.1111\/jpi.12961","article-title":"Melatonin in energy control: Circadian time-giver and homeostatic monitor","volume":"76","author":"Challet","year":"2024","journal-title":"J. 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