{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,27]],"date-time":"2025-12-27T05:17:41Z","timestamp":1766812661241,"version":"3.48.0"},"reference-count":53,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,12,24]],"date-time":"2025-12-24T00:00:00Z","timestamp":1766534400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Science Foundation","award":["CHE-1213838 and CHE-1229339"],"award-info":[{"award-number":["CHE-1213838 and CHE-1229339"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Copper ions are essential trace elements that play critical roles in redox reactions, signal transduction, energy metabolism, and regulation of the central nervous system. However, excess copper can induce cytotoxicity and contribute to various pathological conditions, highlighting the need for sensitive and selective detection methods. We report a novel near-infrared (NIR) optical sensor, IRPhen, based on a heptamethine cyanine scaffold conjugated with a 1,10-phenanthroline Cu2+-binding receptor. IRPhen exhibits strong NIR absorption and emission (Ex: 750 nm, Em: 808 nm), high sensitivity, and good selectivity toward Cu2+ over competing metal ions. Spectroscopic studies revealed a rapid, reversible 1:1 binding interaction with a binding constant of 1.3 \u00d7 106 M\u22121 and a detection limit of 0.286 \u00b5M. The probe demonstrated excellent stability across physiological pH ranges and maintained its performance under competitive conditions. Importantly, IRPhen is cell-permeable and capable of detecting dynamic Cu2+ changes in living fibroblast (WS1) cells using confocal microscopy. This sensor design offers a versatile platform for developing NIR optical sensors to study copper homeostasis, elucidating copper-related biological mechanisms, and potentially developing similar NIR probes for other biologically relevant metal ions.<\/jats:p>","DOI":"10.3390\/s26010130","type":"journal-article","created":{"date-parts":[[2025,12,24]],"date-time":"2025-12-24T16:41:19Z","timestamp":1766594479000},"page":"130","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Heptamethine Cyanine-Based Near-Infrared Optical Sensor for Copper(II) Detection in Aqueous Solutions and Living Cells"],"prefix":"10.3390","volume":"26","author":[{"given":"Ziya","family":"Aydin","sequence":"first","affiliation":[{"name":"Department of Chemistry and Biochemistry and UMass Cranberry Health Research Center, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA"},{"name":"Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003, USA"},{"name":"Vocational School of Technical Sciences, Karamano\u011flu Mehmetbey University, 70200 Karaman, T\u00fcrkiye"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bing","family":"Yan","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry and UMass Cranberry Health Research Center, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA"},{"name":"Biomedical Engineering and Biotechnology Program, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maolin","family":"Guo","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry and UMass Cranberry Health Research Center, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA"},{"name":"Department of Chemistry, University of Massachusetts Amherst, 710 North Pleasant Street, Amherst, MA 01003, USA"},{"name":"Biomedical Engineering and Biotechnology Program, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1016\/j.bpj.2015.11.025","article-title":"How Mammalian Cells Acquire Copper: An Essential but Potentially Toxic Metal","volume":"110","author":"Kaplan","year":"2016","journal-title":"Biophys. 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