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Yang Jun's team at Beijing Forestry University: New progress in natural polymer hydrogels based on the hydrophobic interaction of silk proteins
2019-12-25 Source: Polymer Technology

Natural structural materials, such as silk, animal bones, nacre, and plant fibers, have excellent mechanical strength and toughness that are difficult to achieve with synthetic materials. Experimental and theoretical studies have shown that these materials achieve their special enhancement through the sacrifice of the bonds. Tough enhancement. As a typical sacrificial bond, hydrophobic association effectively dissipates energy and increases fracture toughness when the hydrogel is stressed. At the same time, this reversible crosslinking method allows the hydrogel to heal quickly without the need for external stimuli or healing agents. However, hydrophobically associated gels formed by micellar copolymerization in surfactant sodium lauryl sulfate (SDS) solutions often exhibit lower cytocompatibility and have potential cytotoxicity or Other adverse effects.

To solve this problem, Associate Professor Yang Jun's team proposed a surfactant-free hydrophobic association (HA) hydrogel design strategy to dissolve the hydrophobic monomer octadecyl methacrylate (C18M) in Hydrophobic association was formed in the amphiphilic silk fibroin (RSF) solution, and it was introduced into the sodium alginate ion cross-linking network as a sacrificial bond (Figure 1) to prepare both high compressive strength and self-healing Multifunctional silk protein-based natural high-molecular-weight hydrogel with high compatibility, injectability and biocompatibility.

Figure 1. Schematic construction of SA-RSF HA hydrogel.

2+之间的离子键发生不可逆地断裂,以维持凝胶结构的完整性。 Elastic compression and rheological analysis show that under the action of small strains, the hydrophobic association rate is first destroyed and energy dissipation occurs. As the strain gradually increases, the hydrophobic association weakens, and the relationship between alginate and Ca 2+ Ionic bonds are irreversibly broken to maintain the integrity of the gel structure. According to steady-state shear rheological measurements, HA hydrogels exhibit shear thinning behavior, so HA gels have thixotropy. When the shear stress is removed, the network structure can be quickly restored (Figure 2). In addition, the self-healing process of the HA gel was recorded with an optical microscope. The cracks in the scratches almost healed within 12 hours, indicating that the HA gel has a certain self-healing ability (Figure 3). After the gel sample was cut, cracks occurred on the surface of the gel, and some mixed micelles broke. Due to the migration of the mixed micelles (RSF + C18M) within and between layers, the cracks were first reshaped into circular holes, and then the gel completely healed .

(c) SA,SA-RSF与不同浓度的C18M 的SA-RSF-C18M HA凝胶的稳态剪切粘度η* (37°C)。 (d) HA凝胶的可注射性(甲基蓝染色)。 Figure 2. HA gel's (a) storage modulus (G ') and (b) loss modulus (G "). (C) SA, SA-RSF and SA-RSF-C18M HA with different concentrations of C18M Steady-state shear viscosity η * (37 ° C) of the gel . (D) Injectability of HA gel (methyl blue staining).

Figure 3. (a) Optical microscope image of the self-healing process of SA-RSF-C18M-30 HA gel. (b) Schematic diagram of the gel mechanism before and after self-healing.

In addition, 28 days after mineralization in a simulated body fluid (SBF), calcium phosphate nanoparticles were uniformly distributed on the surface of the gel after mineralization. 2+的捕获,在凝胶表面形成磷化钙纳米颗粒。 This is because silk fibroin contains phosphate ions in the degradation products of SBF solution. Silk fibroin can transfer phosphate ions to the surrounding environment of the gel, which is beneficial for the capture of Ca 2+ and forms calcium phosphide on the surface of the gel. Nanoparticles. It is worth noting that even after 14 days of in vitro culture, the survival rate of mouse osteoblasts (MC3T3-E1) in HA gel can still reach 48.62% (Figure 4).

Figure 4. Comparison of electron micrographs of (a) SA gel and (b) SA-RSF-C18M-30 gel after 20 days of mineralization. Mouse cells (MC3T3-E1) were cultured in HA gel (c) for 1 day and (d) for 14 days.

The above results were recently published on ACS Applied Materials & Interfaces. The title of the paper is Autonomic Self-Healing Silk Fibroin Injectable Hydrogels Formed via Surfactant-Free Hydrophobic Association. The first author is Meng Lei , a doctoral student at Beijing Forestry University, and the corresponding author is Beijing Forestry University. Associate Professor Yang Jun .

Paper link: http://pubs.acs.org/doi/10.1021/acsami.9b19415

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