Yang Weiqing, Lv Lili, Li Xiankai, Han Xiao, Li Mingjie, Li Chaoxu
Group of Biomimetic Smart Materials, CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Songling Road 189, Qingdao 266101, P.R. China.
College of Chemistry and Chemical Engineering, Qingdao University, 308 Ningxia Road, Qingdao, Shandong 266071, P.R. China.
ACS Nano. 2020 Aug 25;14(8):10600-10607. doi: 10.1021/acsnano.0c04686. Epub 2020 Jul 29.
Protein nanostructures in living organisms have attracted intense interests in biology and material science owing to their intriguing abilities to harness ion transportation for matter/signal transduction and bioelectricity generation. Silk nanofibrils, serving as the fundamental building blocks for silk, not only have the advantages of natural abundance, low cost, biocompatibility, sustainability, and degradability but also play a key role in mechanical toughness and biological functions of silk fibers. Herein, cationic silk nanofibrils (SilkNFs), with an ultrathin thickness of ∼4 nm and a high aspect ratio up to 500, were successfully exfoliated from natural cocoon fibers quaternization followed by mechanical homogenization. Being positively charged in a wide pH range of 2-12, these cationic SilkNFs could combine with different types of negatively charged biological nanofibrils to produce asymmetric ionic membranes and aerogels that have the ability to tune ion translocation. The asymmetric ionic aerogels could create an electric potential as high as 120 mV in humid ambient air, whereas asymmetric ionic membranes could be used in ionic rectification with a rectification ratio of 5.2. Therefore, this green exfoliation of cationic SilkNFs may provide a biological platform of nanomaterials for applications as diverse as ion electronics, renewable energy, and sustainable nanotechnology.
由于其在利用离子运输进行物质/信号转导和生物电生成方面具有迷人的能力，生物体中的蛋白质纳米结构在生物学和材料科学领域引起了广泛关注。作为丝绸的基本构建单元，丝纳米纤维不仅具有天然丰富、成本低、生物相容性好、可持续性和可降解性等优点，而且在丝纤维的机械韧性和生物学功能中起着关键作用。在此，通过季铵化随后机械均质化，成功地从天然蚕茧纤维中剥离出厚度约为4 nm、高径比高达500的阳离子丝纳米纤维（SilkNFs）。这些阳离子SilkNFs在2-12的宽pH范围内带正电，可与不同类型的带负电的生物纳米纤维结合，产生具有调节离子转运能力的不对称离子膜和气凝胶。不对称离子气凝胶在潮湿的环境空气中可产生高达120 mV的电势，而不对称离子膜可用于离子整流，整流比为5.2。因此，这种阳离子SilkNFs的绿色剥离可为离子电子学、可再生能源和可持续纳米技术等多种应用提供纳米材料的生物平台。
