Characterization of Agarose Gels in Solvent and Non-Solvent Media
Agarose is known to form a homogeneous thermoreversible gel in an aqueous medium over a critical polymer concentration. The solid-liquid phase transitions are thermoreversible but depend on the molecular structure of the agarose sample tested. The literature has mentioned that agarose gels could rem...
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| Format: | Article |
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MDPI AG
2023-04-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/15/9/2162 |
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| author | Denis C. D. Roux Isabelle Jeacomine Guillaume Maîtrejean François Caton Marguerite Rinaudo |
| author_facet | Denis C. D. Roux Isabelle Jeacomine Guillaume Maîtrejean François Caton Marguerite Rinaudo |
| author_sort | Denis C. D. Roux |
| collection | DOAJ |
| description | Agarose is known to form a homogeneous thermoreversible gel in an aqueous medium over a critical polymer concentration. The solid-liquid phase transitions are thermoreversible but depend on the molecular structure of the agarose sample tested. The literature has mentioned that agarose gels could remain stable in non-solvents such as acetone or ethanol. However, there has been no characterization of their behavior nor a comparison with the gels formed in a good solvent such as water. In the first step of this article, the structure was characterized using <sup>1</sup>H and <sup>13</sup>C NMR in both D<sub>2</sub>O and DMSO-<i>d6</i> solvents. DMSO is a solvent that dissolves agarose regardless of the temperature. First, we have determined a low yield of methyl substitution on the D-galactose unit. Then, the evolution of the <sup>1</sup>H NMR spectrum was monitored as a function of temperature during both increasing and decreasing temperature processes, ranging from 25 to 80 °C. A large thermal hysteresis was obtained and discussed, which aided in the interpretation of rheological behavior. The hysteresis of NMR signals is related to the mobility of the agarose chains, which follows the sol/gel transition depending on the chains’ association with H-bonds between water and the -OH groups of agarose for tightly bound water and agarose/agarose in chain packing. In the second step of the study, the water in the agarose gel was exchanged with ethanol, which is a non-solvent for agarose. The resulting gel was stable, and its properties were characterized using rheology and compared to its behavior in aqueous media. The bound water molecules that act as plasticizers were likely removed during the exchange process, resulting in a stronger and more brittle gel in ethanol, with higher thermal stability compared to the aqueous gel. It is the first time that such gel is characterized without phase transition when passing from a good solvent to a non-solvent. This extends the domains of application of agarose. |
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| language | English |
| last_indexed | 2024-03-11T04:09:29Z |
| publishDate | 2023-04-01 |
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| record_format | Article |
| series | Polymers |
| spelling | doaj.art-cd996bdd3c584250a4544667e149d0162023-11-17T23:36:03ZengMDPI AGPolymers2073-43602023-04-01159216210.3390/polym15092162Characterization of Agarose Gels in Solvent and Non-Solvent MediaDenis C. D. Roux0Isabelle Jeacomine1Guillaume Maîtrejean2François Caton3Marguerite Rinaudo4Univ. Grenoble Alpes, CNRS, Grenoble INP (Institute of Engineering Univ. Grenoble Alpes), LRP, 38000 Grenoble, FranceNMR Centers of RMN-ICMG (FR2607), CERMAV-CNRS, BP53, 38000 Grenoble, FranceUniv. Grenoble Alpes, CNRS, Grenoble INP (Institute of Engineering Univ. Grenoble Alpes), LRP, 38000 Grenoble, FranceUniv. Grenoble Alpes, CNRS, Grenoble INP (Institute of Engineering Univ. Grenoble Alpes), LRP, 38000 Grenoble, FranceBiomaterials Applications, 38000 Grenoble, FranceAgarose is known to form a homogeneous thermoreversible gel in an aqueous medium over a critical polymer concentration. The solid-liquid phase transitions are thermoreversible but depend on the molecular structure of the agarose sample tested. The literature has mentioned that agarose gels could remain stable in non-solvents such as acetone or ethanol. However, there has been no characterization of their behavior nor a comparison with the gels formed in a good solvent such as water. In the first step of this article, the structure was characterized using <sup>1</sup>H and <sup>13</sup>C NMR in both D<sub>2</sub>O and DMSO-<i>d6</i> solvents. DMSO is a solvent that dissolves agarose regardless of the temperature. First, we have determined a low yield of methyl substitution on the D-galactose unit. Then, the evolution of the <sup>1</sup>H NMR spectrum was monitored as a function of temperature during both increasing and decreasing temperature processes, ranging from 25 to 80 °C. A large thermal hysteresis was obtained and discussed, which aided in the interpretation of rheological behavior. The hysteresis of NMR signals is related to the mobility of the agarose chains, which follows the sol/gel transition depending on the chains’ association with H-bonds between water and the -OH groups of agarose for tightly bound water and agarose/agarose in chain packing. In the second step of the study, the water in the agarose gel was exchanged with ethanol, which is a non-solvent for agarose. The resulting gel was stable, and its properties were characterized using rheology and compared to its behavior in aqueous media. The bound water molecules that act as plasticizers were likely removed during the exchange process, resulting in a stronger and more brittle gel in ethanol, with higher thermal stability compared to the aqueous gel. It is the first time that such gel is characterized without phase transition when passing from a good solvent to a non-solvent. This extends the domains of application of agarose.https://www.mdpi.com/2073-4360/15/9/2162agarosemethyl substituentDSCNMRwater retentionrheology |
| spellingShingle | Denis C. D. Roux Isabelle Jeacomine Guillaume Maîtrejean François Caton Marguerite Rinaudo Characterization of Agarose Gels in Solvent and Non-Solvent Media Polymers agarose methyl substituent DSC NMR water retention rheology |
| title | Characterization of Agarose Gels in Solvent and Non-Solvent Media |
| title_full | Characterization of Agarose Gels in Solvent and Non-Solvent Media |
| title_fullStr | Characterization of Agarose Gels in Solvent and Non-Solvent Media |
| title_full_unstemmed | Characterization of Agarose Gels in Solvent and Non-Solvent Media |
| title_short | Characterization of Agarose Gels in Solvent and Non-Solvent Media |
| title_sort | characterization of agarose gels in solvent and non solvent media |
| topic | agarose methyl substituent DSC NMR water retention rheology |
| url | https://www.mdpi.com/2073-4360/15/9/2162 |
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