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Communication

Development of Neutral pH-Responsive Microgels by Tuning Cross-Linking Conditions

1
Laboratory for Chemistry and Life Science Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
2
JST, PRESTO, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
3
Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
4
Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(12), 3367; https://doi.org/10.3390/s20123367
Received: 26 May 2020 / Revised: 9 June 2020 / Accepted: 12 June 2020 / Published: 14 June 2020
(This article belongs to the Special Issue Nanosensors for Biomedical Applications)
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. View Full-Text
Keywords: pH-responsive microgels; NMR relaxation time; volume phase transition; MRI pH-responsive microgels; NMR relaxation time; volume phase transition; MRI
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MDPI and ACS Style

Okada, S.; Takayasu, S.; Tomita, S.; Suzuki, Y.; Yamamoto, S. Development of Neutral pH-Responsive Microgels by Tuning Cross-Linking Conditions. Sensors 2020, 20, 3367. https://doi.org/10.3390/s20123367

AMA Style

Okada S, Takayasu S, Tomita S, Suzuki Y, Yamamoto S. Development of Neutral pH-Responsive Microgels by Tuning Cross-Linking Conditions. Sensors. 2020; 20(12):3367. https://doi.org/10.3390/s20123367

Chicago/Turabian Style

Okada, Satoshi, Satoko Takayasu, Shunsuke Tomita, Yoshio Suzuki, and Shinya Yamamoto. 2020. "Development of Neutral pH-Responsive Microgels by Tuning Cross-Linking Conditions" Sensors 20, no. 12: 3367. https://doi.org/10.3390/s20123367

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