{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,18]],"date-time":"2026-10-18T17:00:18Z","timestamp":1792342818326,"version":"4.4.0"},"reference-count":52,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T00:00:00Z","timestamp":1788393600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"U. A. Whitaker College of Engineering, Florida Gulf Coast University"},{"id":[{"id":"https:\/\/ror.org\/05tc5bm31","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>A miniature label-free biosensor based on a chemically etched single-mode optical fiber (SMF) is reported for the detection of matrix metalloproteinase-8 (MMP-8), a salivary biomarker of active periodontitis with a clinical decision threshold of 20 ng\/mL. Fibers etched in 48% hydrofluoric acid to a waist diameter of 16.0 \u00b1 1.4 \u00b5m gave a mean refractive index (RI) sensitivity of 376.8%\/RIU and an RI limit of detection (LOD) of 5.9 \u00d7 10\u22124 RIU. Fibers were tested with MMP-8 spiked into phosphate-buffered saline (PBS) and into saliva over 0\u2013200 ng\/mL using a post-rinse protocol with per-fiber matrix subtraction. Dose\u2013responses followed a Langmuir isotherm (Kd = 7.1 ng\/mL in PBS, 12.7 ng\/mL in saliva), with cohort LODs of 0.043 and 0.52 ng\/mL, both well below the threshold. MMP-9 (100 ng\/mL) and human serum albumin (1 mg\/mL) gave negligible responses (\u22642.7%, versus 68.2% for MMP-8 at 100 ng\/mL); antibody immobilization was confirmed by confocal immunofluorescence. A commercial sandwich ELISA on the same spike series gave a matched-matrix LOD of 41.1 ng\/mL, nearly two orders of magnitude higher. This performance requires no metal coating, nanostructuring, label, or signal amplification, only a single wet-etching step on stock telecommunications fiber.<\/jats:p>","DOI":"10.3390\/bios16090491","type":"journal-article","created":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T10:10:33Z","timestamp":1788430233000},"page":"491","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Periodontal Disease Diagnosis by a Chemically Etched Single-Mode Fiber-Optic Biosensor for Label-Free Detection of Matrix Metalloproteinase-8 (MMP-8)"],"prefix":"10.3390","volume":"16","author":[{"suffix":"Jr.","given":"Rigoberto","family":"Tovar","sequence":"first","affiliation":[{"name":"Department of Bioengineering, Civil Engineering, and Environmental Engineering, U. A. Whitaker College of Engineering, Florida Gulf Coast University, 10501 FGCU Boulevard South, Fort Myers, FL 33965, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1555-3591","authenticated-orcid":false,"given":"Sarkis","family":"Sozkes","sequence":"additional","affiliation":[{"name":"Department of Bioengineering, Civil Engineering, and Environmental Engineering, U. A. Whitaker College of Engineering, Florida Gulf Coast University, 10501 FGCU Boulevard South, Fort Myers, FL 33965, USA"},{"name":"Department of Biomaterials, Biomedical Engineering Corlu Faculty, Tekirdag Namik Kemal University, Y\u0131lmaz Alpaslan Cd. No:25, 59850 Tekirdag, Turkey"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6423-3781","authenticated-orcid":false,"given":"Marzhan","family":"Sypabekova","sequence":"additional","affiliation":[{"name":"Department of Bioengineering, Civil Engineering, and Environmental Engineering, U. A. 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