Axpe Eneko, Duraj-Thatte Anna, Chang Yin, Kaimaki Domna-Maria, Sanchez-Sanchez Ana, Caliskan H Burak, Dorval Courchesne Noémie-Manuelle, Joshi Neel S
Nanoscience Centre, Department of Engineering, Cambridge University, 11 JJ Thomson Ave., Cambridge CB3 0FF, United Kingdom.
Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Cir., Boston, Massachusetts 02115, United States.
ACS Biomater Sci Eng. 2018 Jun 11;4(6):2100-2105. doi: 10.1021/acsbiomaterials.8b00364. Epub 2018 May 10.
Alginate hydrogels are biocompatible, biodegradable, low-cost, and widely used as bioinks, cell encapsulates, three-dimensional culture matrices, drug delivery systems, and scaffolds for tissue engineering. Nevertheless, their limited stiffness hinders their use for certain biomedical applications. Many research groups have tried to address this problem by reinforcing alginate hydrogels with graphene, carbon nanotubes, or silver nanoparticles. However, these materials present nanotoxicity issues, limiting their use for biomedical applications. Other studies show that electrospinning or wet spinning can be used to fabricate biocompatible, micro- and nanofibers to reinforce hydrogels. As a relatively simple and cheap alternative, in this study we used bioengineered bacteria to fabricate amyloid curli fibers to enhance the stiffness of alginate hydrogels. We have fabricated for the first time bioengineered amyloid curli fibers-hydrogel composites and characterized them by a combination of (i) atomic force microscopy (AFM) to measure the Young's modulus of the bioengineered amyloid curli fibers and study their topography, (ii) nanoindentation to measure the Young's modulus of the amyloid curli fibers-alginate nanocomposite hydrogels, and (iii) Fourier-transform infrared spectroscopy (FTIR) to analyze their composition. The fabricated nanocomposites resulted in a highly improved Young's modulus (up to 4-fold) and showed very similar physical and chemical properties, opening the window for their use in applications where the properties alginate hydrogels are convenient but do not match the stiffness needed.
海藻酸水凝胶具有生物相容性、可生物降解、成本低等特点，被广泛用作生物墨水、细胞封装材料、三维培养基质、药物递送系统以及组织工程支架。然而，其有限的硬度阻碍了它们在某些生物医学应用中的使用。许多研究小组试图通过用石墨烯、碳纳米管或银纳米颗粒增强海藻酸水凝胶来解决这个问题。然而，这些材料存在纳米毒性问题，限制了它们在生物医学应用中的使用。其他研究表明，静电纺丝或湿法纺丝可用于制造生物相容性的微纤维和纳米纤维以增强水凝胶。作为一种相对简单且廉价的替代方法，在本研究中，我们使用生物工程细菌制造淀粉样卷曲纤维以提高海藻酸水凝胶的硬度。我们首次制造了生物工程淀粉样卷曲纤维 - 水凝胶复合材料，并通过以下方法对其进行了表征：（i）原子力显微镜（AFM）测量生物工程淀粉样卷曲纤维的杨氏模量并研究其形貌；（ii）纳米压痕测量淀粉样卷曲纤维 - 海藻酸钠纳米复合水凝胶的杨氏模量；（iii）傅里叶变换红外光谱（FTIR）分析其组成。所制备的纳米复合材料的杨氏模量得到了显著提高（高达4倍），并且显示出非常相似的物理和化学性质，为其在海藻酸水凝胶性质合适但刚度不符合要求的应用中打开了窗口。
