| 학회 | 한국공업화학회 |
| 학술대회 | 2015년 봄 (04/29 ~ 05/01, BEXCO (부산)) |
| 권호 | 19권 1호 |
| 발표분야 | 생체재료_포스터 |
| 제목 | Stability Increase of Ca2+-Alginate Hydrogels by Spontaneous Ionic-to-Covalent bond Exchange |
| 초록 | Alginate is a linear polysaccharide extracted from brown algae and composed of homopolymeric blocks of (1–4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G). The most representative features of alginates are the stiffnesses of their polymer chains and their affinities to various transition metal cations, such as Cd2+, Ni2+, or Mn2+, which could be exploited for metal removal in environmental science and engineering. Recently, applications have been expanded to energy storage devices. For example, alginate is used as a silicon anode binder in Li-ion batteries due to the stiffness of the alginate backbone. In addition to environmental sciences and energy storage technologies, the most well-known research field utilizing alginate has been biomaterial sciences. The prompt formation of alginate gels in the presence of calcium ions in aqueous solutions (known as Ca2+-alginate gel) has been a useful method of encapsulating and then releasing various macromolecular pharmaceuticals. An early example is the encapsulation of islets to release insulin upon the infusion of glucose for treating diabetes. Additionally, alginate gels are used for local delivery of incorporated vascular endothelial growth factor (VEGF) to enhance angiogenesis in peripheral tissues. Despite the widespread uses, the major drawback of Ca2+-alginate gels is rapid gel dissolution due to ionic bond dissociation between the encapsulated Ca2+ ions and the carboxylic acid (R-COO-) groups along alginate backbones. This issue prevents the widespread use of Ca2+-alginate hydrogels for drug delivery or tissue engineering scaffolds. Methods to overcome this gel dissolution have been developed mostly using cationic polymer coatings. The coatings performed with poly L-lysine, chitosan, or poly(ethylenimine) on hydrogel surfaces showed increased physical stabilities, but nonetheless, the dissociation of the coated polymers is unavoidable, resulting in problems for long-term stability. Alternatively, the formation of covalent bonds via carbodiimide conjugation or reductive amination chemistries increases the physical stability. However, these approaches are generally not compatible with in situ encapsulations of cells or proteins due to the presence of coupling agents. Thus, we hypothesized that combining these two approaches (ionic and covalent linkages) might provide a new method to prepare alginate hydrogels. Our new approach uses ionic couplings for cell encapsulation initially and later in time the covalent bonds are formed, which gradually replace the ionic bonds, thus increasing the physical stability of the alginate gel. We called this alginate gel ‘STAPLE’, an abbreviation for Stable Alginate gel Prepared via Linkage Exchange from ionic to covalent bonds. The key chemistry in STAPLE is the ionic to covalent bond transitions, where the catechol moieties tethered along alginate chains are slowly oxidized to catecholquinone. The catecholquinone mediated crosslinking kinetics are well matched with the kinetics of Ca2+ dissociation at pH 7.4 and 37 °C. Thus, the original physicochemical integrity of the hydrogel is preserved even after the Ca2+ dissociation. This novel method to prepare alginate hydrogels may increase the potential utility in a variety of biomedical applications. |
| 저자 | 홍상현, 이해신 |
| 소속 | KAIST |
| 키워드 | alginate; hydrogel; catechol |
