Design of hydrogels and development of surface modification method utilizing smart molecules = 스마트 분자를 이용한 하이드로젤 제조 및 표면 개질법 개선

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According to the progress in material science, smart systems capable of incorporating functions of sensing, actuation, and response to environmental changes, have been gained attention in the various appli-cations. For instance, since the development of first hydrogel by Witchler and Lim, hydrogels with soft texture and large amount of water, have been utmost candidate for biomedical fields as well as tissue engineering, carriers for drug delivery, and even in cosmetics. And, nowadays, the uses of hydrogels have expanded to fabricate soft material devices, actuators, sensors, self-healable materials. However, it is difficult to design smart hydrogels due to the demand on complicate systems, and therefore, facile methods are required. In nature, the marine creatures often shows strong adhesiveness to surfaces. Especially, mussel (Mytilus edulis) secretes adhesive proteins, called Mytilus edulis foot protein (Mefp), which have an unusual amino acid, L-3,4-dihydroxy-L-phenylalanine (DOPA). This interesting mussel adhesion is derive from cate-chol moiety in DOPA showing self-polymerization in basic condition, resulting in adhesiveness to various ma-terials including rocks, ships, and other synthetic materials. Moreover, this catechol moiety can undergoes various covalent/non-covalent reactions such as Michael-type addition reactions, Schiff-base formations, and π-cation bonds. Thus, catechol moiety and catechol-tethered polymers might have high potentials to be used in smart systems. Furthermore, boronic acid consisted of trivalent boron-containing compound with di-hydroxyl group is also an attractive molecule. Unlike DOPA and other catechol moieties, boronic acid are synthetic compound which is come from acidified borax and carbon dioxide. However, The unique properties as a Lewis acids due to two deficient electrons, and dynamic ester formation with cis-diol group can provide significant role in smart system. Utilizing smart molecules, we synthesized a catechol-, boronic acid-conjugated alginate (Alginate-C, Alginate-BA) to design smart hydrogels. In thesis dissertation, we propose the novel hydrogels to improve the $alginate-Ca^{2+}$ hydrogel, and augment multi-functionalities. In addition, we also developed conventional sur-face modification method by controlling kinetics of self-polymerization with dopamine. The first part (Chapter 2) of my thesis is the design of novel calcium-alginate hydrogel. Calcium-alginate hydrogels have extensively utilized as scaffolding materials in tissue regeneration and drug delivery. However, the major drawback to the calcium-alginate gels is the rapid dissolution of the alginate polymers caused by the loss of the ionic interaction between $Ca^{2+}$ and $COO^-$. Methods to overcome the dissolution of alginate hydrogel are achieved mostly by additional cationic polymer coating on surfaces of the hydrogels. Herein, we demonstrate that the additional coating by cationic polymers is not necessary to maintain the original physicochemical integrity of the hydrogels. When using polyphenol-tethered alginate as a backbone polymer to prepare calcium alginate hydrogel at pH 7.4, the tethered polyphenol undergoes relatively slow crosslinking, which well matches the kinetics of the calcium dissociation. Thus, the original physicochemical integrity of the hydrogel maintained even after the calcium dissociation. This novel method to prepare the alginate hydrogel may increase the potential utility in a variety of biomedical applications. The second part (Chapter 3 and 4) is the design of novel multi-functional hydrogel utilizing boronic acid, and its application. For the increasing demand of soft materials with wide range of applications, hydro-gels with variety of functions (e.g. self-healing, stimuli-responsive, stretchability, and etc.) have been devel-oped. However, most functional hydrogels, developed so far, have vulnerable point in preparation method; requiring multi-components in hydrogel. Moreover, none of the studies have achieved multi-functions utiliz-ing ‘single’ component. Herein, we designed single component hydrogel prepared by alginate-boronic acid conjugate by establishing dynamic bond formation, and the alginate-BA hydrogel which is named SMART (Stimuli-sensitive and Multifunctional Alginate gel prepared via bond Rearrangement and Transfer) exhibited various multi-functionalities simultaneously such as self-healing, re-shaping, pH-, glucose-sensitivity, stretch-ability, and adhesive properties. In addition, the continuous bond dissociation and association was further studied in microscopic level by AFM pull-off experiments. We suggest that this novel hydrogel have potential feasibility in wide range of biomedical applications. One of the most emerging issues is the developing techniques for gluing hydrogels. The purposes of gluing hydrogels are i) understanding cell-cell or cell-protein interactions, ii) substituents for tissue adhesives, and iii) hybridization of hydrogels with different characteristics. However, in most cases, hydrogels are at-tached through complementary interactions (e.g. ionic or hydrophobic interactions, and molecular recogni-tion) that can use particular hydrogels, and are required pre-designed. Here, we propose a new approach to glue hydrogels utilizing alginate-BA hydrogel glue. This novel method is notably different from other conven-tional techniques in its facile method and adhesion to versatile hydrogels. The robust assembling of hydrogels was evaluated by both quantitative and qualitative methods. We expect that this novel hydrogel glue can provide potential applications in the fields of soft material actuators and biological glues. Finally, we have developed and optimized traditional surface modification method with poly-doapmine (Chapter 5). Polydopamine (pDA) coating has been extensively implemented in many areas rang-ing from fundamental surface science to practical applications due to its material-independent capability of surface functionalization. Despite the successful use of pDA, the current pDA coating method has a signifi-cant drawback represented by long coating time (typically overnight). Similar to layer-by-layer assembly, the long coating time has been a barrier for practical applications. Furthermore, oxidation of dopamine, which is an essential chemistry for surface modification, prevents from repeatable use of the dopamine solution in a traditional dip-coating method. Therefore, the development of an approach to implement sprayable, ultra-fast pDA (f-pDA) coating is necessary. Herein, we analyzed physicochemical factors that affected the coating kinetics of pDA and found the following optimum condition: 40 mM dopamine and 80 mM of $NaIO_4$ dis-solved in a pH 9.5 aqueous buffer. Within one minute, virtually any surface could be functionalized with pDA. This enhanced pDA coating speed enabled us to establish a spray system by mixing two solutions of dopamine and pH titrated $NaIO_4$, which is suitable for large-scale surface coating applications in industrial roll-to-roll processes and other related applications. Using the spray, ultrafast pDA coating, we prepared pDA-functionalized poly(ethylene) separator membranes, resulting in increases of power of Li-ion batteries. Addi-tionally, non-adhesive surfaces were dramatically changed to mammalian cell-friendly interfaces for mam-malian cell attachment within several minutes.
Lee, Haeshinresearcher이해신researcher
한국과학기술원 :화학과,
Issue Date

학위논문(박사) - 한국과학기술원 : 화학과, 2016.2 ,[ix, 69 p. :]


hydrogel; catechol; boronic acid; surface modification; functionality; 하이드로젤; 카테콜; 보론산; 표면개질; 기능성

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