{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T22:26:54Z","timestamp":1777588014512,"version":"3.51.4"},"reference-count":18,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2013,1,21]],"date-time":"2013-01-21T00:00:00Z","timestamp":1358726400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Microparticles consisting of the thermal responsive polymer N-isopropyl acrylamide (polyNIPAM), a metal ion-binding ligand and a fluorophore pair that undergoes fluorescence resonance energy transfer (FRET) have been prepared and characterized. Upon the addition of Cu(II), the microparticles swell or contract depending on whether charge is introduced or neutralized on the polymer backbone. The variation in microparticle morphology is translated into changes in emission of each fluorophore in the FRET pair. By measuring the emission intensity ratio between the FRET pair upon Cu(II) addition, the concentration of metal ion in solution can be quantified. This ratiometric fluorescent indicator is the newest technique in an ongoing effort to use emission spectroscopy to monitor Cu(II) thermodynamic activity in environmental water samples.<\/jats:p>","DOI":"10.3390\/s130101341","type":"journal-article","created":{"date-parts":[[2013,1,21]],"date-time":"2013-01-21T10:58:53Z","timestamp":1358765933000},"page":"1341-1352","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Fluorescent Ratiometric Indicators Based on Cu(II)-Induced Changes in Poly(NIPAM) Microparticle Volume"],"prefix":"10.3390","volume":"13","author":[{"given":"John","family":"Osambo","sequence":"first","affiliation":[{"name":"Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"W.","family":"Seitz","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"Daniel","family":"Kennedy","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA"},{"name":"Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5673-8694","authenticated-orcid":false,"given":"Roy","family":"Planalp","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"Aaron","family":"Jones","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA"}]},{"given":"Randy","family":"Jackson","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA"}]},{"given":"Shawn","family":"Burdette","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA"}]}],"member":"1968","published-online":{"date-parts":[[2013,1,21]]},"reference":[{"key":"ref_1","unstructured":"Meyer, J.S. (2007). Effects of Water Chemistry on the Bioavailability and Toxicity of Waterborne Cadmium, Copper, Nickel, Lead, and Zinc to Freshwater Organisms; Society of Environmental Toxicology and Chemistry, SETAC Press."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/S1532-0456(02)00112-6","article-title":"The biotic ligand model: A historical overview","volume":"133","author":"Paquin","year":"2002","journal-title":"Comp. Biochem. Physiol. C Toxicol. Pharmacol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1016\/S1462-9011(00)00045-9","article-title":"Revisiting the aquatic impacts of copper discharged by water-cooled copper alloy condensers used by power and desalination plants","volume":"3","author":"Paquin","year":"2000","journal-title":"Environ. Sci. Pol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1057","DOI":"10.1038\/nprot.2006.172","article-title":"Measuring calcium signaling using genetically targetable fluorescent indicators","volume":"1","author":"Palmer","year":"2006","journal-title":"Nature Protocol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1007\/s10863-012-9427-2","article-title":"Quantitative imaging of mitochondrial and cytosolic free zinc levels in an in vitro model of ischemia\/reperfusion","volume":"44","author":"McCranor","year":"2012","journal-title":"J. Bioenerg. Biomembr."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"5006","DOI":"10.1039\/c1an15479f","article-title":"A ratiometric fluorescent metal ion indicator based on dansyl labeled poly(n-isopropylacrylamide) responds to a quenching metal ion","volume":"136","author":"Du","year":"2011","journal-title":"Analyst"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"3439","DOI":"10.1021\/cm901070a","article-title":"Enhancing detection sensitivity of responsive microgel-based Cu(II) chemosensors via thermo-induced volume phase transitions","volume":"21","author":"Liu","year":"2009","journal-title":"Chem. Mater."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1002\/pat.986","article-title":"Thermo and pH sensitive fluorescent polymer sensor for metal cations in aqueous solution","volume":"19","author":"Liu","year":"2008","journal-title":"Polymer. Adv. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"4734","DOI":"10.1039\/c2an35771b","article-title":"Intermolecular approach to metal ion indicators based on polymer phase transitions coupled to fluorescence resonance energy transfer","volume":"137","author":"Yao","year":"2012","journal-title":"Analyst"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"11367","DOI":"10.1021\/la901377h","article-title":"Metal-chelating and dansyl-labeled poly(n-isopropylacrylamide) microgels as fluorescent Cu2+ sensors with thermo-enhanced detection sensitivity","volume":"25","author":"Yin","year":"2009","journal-title":"Langmuir"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"12213","DOI":"10.1021\/jp1052369","article-title":"Fret-derived ratiometric fluorescent K+ sensors fabricated from thermoresponsive poly(n-isopropylacrylamide) microgels labeled with crown ether moieties","volume":"114","author":"Yin","year":"2010","journal-title":"J. Phys. Chem. B"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1016\/0079-6700(92)90023-R","article-title":"Poly (n-isopropylacrylamide)\u2014Experiment, theory and application","volume":"17","author":"Schild","year":"1992","journal-title":"Prog. Polym. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2373","DOI":"10.1007\/s00216-010-3848-8","article-title":"Utilization of microparticles in next-generation assays for microflow cytometers","volume":"398","author":"Kim","year":"2010","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1039\/b905502a","article-title":"Microparticle encoding technologies for high-throughput multiplexed suspension assays","volume":"1","author":"Birtwell","year":"2009","journal-title":"Integr. Biol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/S0003-2670(99)00608-X","article-title":"Derivatized, swellable polymer microspheres for chemical transduction","volume":"400","author":"Seitz","year":"1999","journal-title":"Anal. Chim. Acta"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1021\/ic050396l","article-title":"Electronic energy-transfer rate constants for geometrical isomers of a bichromophoric macrocyclic complex","volume":"45","author":"Moore","year":"2006","journal-title":"Inorg. Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2762","DOI":"10.1016\/j.polymer.2009.04.024","article-title":"Xanthene dyes\/amine as photoinitiators of radical polymerization: A comparative and photochemical study in aqueous medium","volume":"50","author":"Encinas","year":"2009","journal-title":"Polymer"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"328","DOI":"10.1080\/10601320701865960","article-title":"Synthesis of poly(methyl methacrylate) labeled with fluorescein moieties via atom transfer radical polymerization","volume":"45","author":"Li","year":"2008","journal-title":"J. Macromol. Sci. Pure Appl. 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