PH/temperature sensitive chitosan-g-(PA-PEG) aqueous solutions as new thermogelling systems

Ji Hye Jang, Yoon Mi Choi, Yun Young Choi, Min Kyung Joo, Min Hee Park, Bo Gyu Choi, Eun Young Kang, Byeongmoon Jeong

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

As a new thermal gelling polymer aqueous solution, we are reporting a poly(ethylene glycol)-poly(alanine) grafted chitosan (CS-g-(PA-PEG)) system. The sol-gel transition temperature and the modulus of the in situ-formed thermal gel at 37°C changed 17 → 27 →32°C and 396 → 241 → 43 Pa, respectively, as the pH increased from 3.0 to 6.5 and to 9.0. The mechanism of such a pH/temperature sensitive behaviour of the CS-g-(PA-PEG) aqueous solution was investigated by studying changes in the conformation of chitosan, polyalanine and PEG of the CS-g-(PA-PEG). As the temperature increased, ammonium groups of the chitosan partially deprotonated to a neutral form, the α-helical content of the polyalanine increased and molecular motion of the PEG decreased. Such changes cooperatively increase the hydrophobicity and viscosity of CS-g-(PA-PEG), resulting in the sol-gel transition of the polymer aqueous solution with increasing temperature. As the pH increased, ammonium groups of the chitosan deprotonated to a neutral form and the α-helical content of polyalanine decreased, which induce a change in the nanoassembly of the polymer. CS-g-(PA-PEG) significantly increased the gel modulus of a previously reported PEG grafted chitosan (CS-g-PEG) thermal gel by incorporating the α-helical polyalanine moieties between CS and PEG. The CS-g-(PA-PEG) could be a promising biomaterial as a new robust thermogel with pH and temperature sensitivity.

Original languageEnglish
Pages (from-to)5484-5491
Number of pages8
JournalJournal of Materials Chemistry
Volume21
Issue number14
DOIs
StatePublished - 14 Apr 2011

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