{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:54:56Z","timestamp":1760237696382,"version":"build-2065373602"},"reference-count":36,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2020,6,14]],"date-time":"2020-06-14T00:00:00Z","timestamp":1592092800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002241","name":"Japan Science and Technology Agency","doi-asserted-by":"publisher","award":["JPMJPR1881"],"award-info":[{"award-number":["JPMJPR1881"]}],"id":[{"id":"10.13039\/501100002241","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["JP19K15719","JP18H05985"],"award-info":[{"award-number":["JP19K15719","JP18H05985"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012018","name":"Research Foundation for Opto-Science and Technology","doi-asserted-by":"publisher","award":["A H30 research grant"],"award-info":[{"award-number":["A H30 research grant"]}],"id":[{"id":"10.13039\/501100012018","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Polymer microgels that respond in a range of neutral pH can be useful for the development of molecular imaging tools and drug-delivery carriers. Here, we describe a simple approach in developing microgels that undergo volume phase transitions and substantial nuclear magnetic resonance (NMR) relaxometric changes within a narrow pH range of 6.4 to 7.4. The pH-responsive microgels were synthesized using methacrylic acid and a series of ethylene glycol dimethacrylate cross-linkers with repeating units of ethylene glycol that range from one to four. NMR relaxometry demonstrated that the transverse relaxation time (T2) of a suspension containing microgels that were cross-linked with diethylene glycol dimethacrylate sharply decreases at the pH where volume phase transition occurs. The polymer microgels cross-linked with 40 and 45 mol% of diethylene glycol dimethacrylate caused about 50% T2 reduction with decreasing pH from 6.8 to 6.4. These results demonstrated that responses of microgels to a range of neutral pH can be easily tuned by using appropriate cross-linkers with certain cross-linking degree. This approach can be useful in developing highly sensitive molecular sensors for magnetic resonance imaging (MRI) of tissue pH values.<\/jats:p>","DOI":"10.3390\/s20123367","type":"journal-article","created":{"date-parts":[[2020,6,15]],"date-time":"2020-06-15T05:56:27Z","timestamp":1592200587000},"page":"3367","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Development of Neutral pH-Responsive Microgels by Tuning Cross-Linking Conditions"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2776-9509","authenticated-orcid":false,"given":"Satoshi","family":"Okada","sequence":"first","affiliation":[{"name":"Laboratory for Chemistry and Life Science Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan"},{"name":"JST, PRESTO, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan"},{"name":"Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan"}]},{"given":"Satoko","family":"Takayasu","sequence":"additional","affiliation":[{"name":"Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0586-6976","authenticated-orcid":false,"given":"Shunsuke","family":"Tomita","sequence":"additional","affiliation":[{"name":"Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan"}]},{"given":"Yoshio","family":"Suzuki","sequence":"additional","affiliation":[{"name":"Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0505-8848","authenticated-orcid":false,"given":"Shinya","family":"Yamamoto","sequence":"additional","affiliation":[{"name":"Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan"}]}],"member":"1968","published-online":{"date-parts":[[2020,6,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"C195","DOI":"10.1152\/ajpcell.1994.267.1.C195","article-title":"31P-MRS measurements of extracellular pH of tumors using 3- aminopropylphosphonate","volume":"267","author":"Gillies","year":"1994","journal-title":"Am. 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