Pure collagen materials are expensive with poor mechanical properties, which need modifications in most cases. As the degradation product of collagen, gelatin is cheap, degradable and biocompatible, but few literatures have reported the research about gelatin-collagen composite materials. This is because gelatin and collagen have different soluble temperatures—gelatin is soluble in hot water (≥30 °C) and swells in cold water. However, a low temperature (2–10 °C) is required to prepare and store collagen solution, and neutral collagen solution denatures quickly above the room temperature. In this study, gelatin was ground into powders and swelled in neutral bovine tendon pepsin-soluble collagen solution (BPSC) to form a homogeneous gelatin-collagen mixture, in light of the swelling characteristics of gelatin in cold water. The assembly properties and gel properties of this composite material were further studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) test results showed that the bovine tendon collagen had typical type-I collagen structural characterizations with two α chains of about 100 kDa and one β chain of about 200 kDa; while the SDS-PAGE pattern of gelatin displayed bands continuously distributed from 30 to 200 kDa. Amino acid composition analysis test indicated that the content of polar amino acids and the sum of acidic and base amino acids for gelatin were higher than that of BPSC. Studies on gel properties demonstrated that gelatin-collagen mixed solution had collagen-like assembly characteristics and assembly kinetics. The moduli of the assembled gel at 35 °C were equivalent to that of pure bovine tendon collagen system; moreover, the system moduli didn’t change with time with elastic moduli (G′) of about 40 Pa. However, at 25 °C, the moduli of gelatin-collagen composite hydrogel increased with the extension of time, its G′ increased about 18 times within 8 h, and the ratio of elastic modulus to viscous modulus (G″) increased 4.6 times, showing a significant aging effect of structural strength. Meanwhile, the mechanical strength of the composite hydrogel was also regulated by temperature—the gel was highly elastic (G′≈3,000 Pa, G′>>G″) at a low temperature (5 °C); as the temperature rose, the system moduli gradually decreased and the elastic gel transformed into waterlike fluid at 50 °C little by little. What’s more, gelatin-collagen composite hydrogel also had reversible sol-gel performances and self-healing capability similar to the gelatin hydrogel. This novel preparation method for preparing composite materials and the resultant composite hydrogel are expected to be used in the fields of natural food gels, injectable hydrogels, cell scaffolds, drug sustained-release materials and so on, and improve and promote the processing performances, price and large-scale production of collagen-based materials.

中文翻译：

---

明胶修饰胶原蛋白的新方法和明胶-胶原复合水凝胶的粘弹性研究

纯胶原蛋白材料昂贵且机械性能差，在大多数情况下需要进行修改。明胶作为胶原蛋白的降解产物，价格便宜，可降解且具有生物相容性，但很少有文献报道明胶-胶原蛋白复合材料的研究。这是因为明胶和胶原蛋白具有不同的可溶温度-明胶可溶于热水（≥30°C）并在冷水中溶胀。但是，制备和储存胶原蛋白溶液需要低温（2–10°C），中性胶原蛋白溶液在高于室温时会迅速变性。在这项研究中，鉴于明胶在冷水中的溶胀特性，将明胶研磨成粉末，然后在中性牛腱胃蛋白酶可溶性胶原蛋白溶液（BPSC）中溶胀，形成均匀的明胶-胶原蛋白混合物。对该复合材料的组装性能和凝胶性能进行了进一步研究。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）测试结果表明，牛腱胶原蛋白具有典型的I型胶原蛋白结构特征，其中两个约100kDa的α链和约200kDa的一条β链；明胶的SDS-PAGE模式显示的条带从30到200 kDa连续分布。氨基酸组成分析试验表明，明胶的极性氨基酸含量和酸性，碱性氨基酸含量均高于BPSC。凝胶性能研究表明，明胶-胶原蛋白混合溶液具有类似胶原蛋白的组装特性和组装动力学。组装后的凝胶在35°C时的模量与纯牛腱胶原系统的模量相同；此外，在约40 Pa的弹性模量（G '）下，系统模量没有随时间变化。但是，在25°C下，明胶-胶原复合水凝胶的模量随时间的延长而增加，G '在8 h内增加了18倍，弹性模量与粘性模量之比（G ″）增加了4.6倍，显示出明显的结构强度时效效应。同时，复合水凝胶的机械强度还通过调节温度的凝胶是高度弹性的（g ^ '≈3,000Pa时，ģ '>> ģ”）在低温（5°C）下；随着温度的升高，系统模量逐渐降低，并且在50°C时，弹性凝胶逐渐转变为水状流体。而且，明胶-胶原复合水凝胶也具有与明胶水凝胶相似的可逆溶胶-凝胶性能和自愈能力。这种制备复合材料的新方法及其所得的复合水凝胶有望用于天然食品凝胶，可注射水凝胶，细胞支架，药物缓释材料等领域，并改善和促进加工性能，价格。大规模生产胶原蛋白基材料。