title: Freeze-thaw induced gelation of alginates.
abstract: Adding divalent ions or lowering pH below the pKa values of alginate monomers are common ways in preparing alginate gels. Herein a new way of preparing alginate gels using freeze-thaw technique is described. Solvent crystallization during freezing drove the polymers to associate into certain structures that became the junction zones of hydrogels after thawing. It enabled the preparation of alginate gels at pH 4.0 and 3.5, two pH at which the gel could not be formed previously. At pH 3.0 where alginate gel could be formed initially, applying freeze-thaw treatment increased the gel storage modulus almost 100 times. The formation of hydrogels and the resulting gel properties, such as dynamic moduli and gel syneresis were influenced by the pH values, number of freeze-thaw cycles, alginate concentrations, and ionic strengths. The obtained hydrogels were soft and demonstrated a melting behavior upon storage, which may find novel applications in the biomedical industry.
authors.affiliation: Glycomics and Glycan Bioengineering Research Center (GGBRC), College of Food Science and Technology, Nanjing Agricultural University, Weigang 1, Nanjing 210095, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: College of Science, Nanjing Agricultural University, Weigang 1, Nanjing 210095, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.affiliation: Glycomics and Glycan Bioengineering Research Center (GGBRC), College of Food Science and Technology, Nanjing Agricultural University, Weigang 1, Nanjing 210095, People's Republic of China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Glycomics and Glycan Bioengineering Research Center (GGBRC), College of Food Science and Technology, Nanjing Agricultural University, Weigang 1, Nanjing 210095, People's Republic of China. Electronic address: twu@njau.edu.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
mesh_terms: D000464:Alginates / Q000737:chemistry*; D003460:Crystallization; D005615:Freezing; D020100:Hydrogels / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D011108:Polymers / Q000737:chemistry
chemical_list: D000464:Alginates; D020100:Hydrogels; D011108:Polymers
keywords: Alginate gel; Freeze-thaw; Gel properties; Induce