Yao Shenglian, Wang Xiumei, Liu Xi, Wang Ronghan, Deng Changsheng, Cuil Fuzhai
Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Institute for Regenerative Medicine and Biomimetic Materials, Tsinghua University, Beijing 100084, China.
J Nanosci Nanotechnol. 2013 Jul;13(7):4752-8. doi: 10.1166/jnn.2013.7197.
Nanofibers exist ubiquitously in natural extracellular matrix (ECM) of all kinds of human tissues forming hydrated interwoven network. Electrospinning nanotechnology has been proven to be a powerful technique to fabricate controllable nanofibers mimicking the natural ECM structures. Hyaluronic acid (HA), as a critical component of natural ECM, has been widely used in tissue engineering and regenerative medicine. In this study, pure HA nanofibers with average diameter of 33 +/- 5 nm, 59 +/- 12 nm, 79 +/- 12 nm and 113 +/- 19 nm were successfully prepared using different electrospinning parameters. The effect of the ambient relative humidity on HA electrospinnability was investigated for the first time in detail, which was proven to be one of the most important factors to control the morphology of HA nanofibers beside the solution properties. A critical value of humidity for a defined HA solution was observed, only below which HA nanofibers with similar diameters and morphologies could be successfully obtained. When the ambient relative humidity was higher than the critical value, the HA nanofibers started dissolving at the cross points and even fused together forming a spreading layer. Moreover, only a small amount of N, N-Dimethylformamide (DMF) was found to be required to promote the electrospinnability of HA solution by mixing with water as solvents. With the increase in the DMF content, the surface tension of the solution decreased significantly, which was thought to be benefit for the stable Taylor cone and fluid jet formation in electrospinning. At the same time, it should be noted that the conductivity of the solution also decreased with the increase of DMF content in the solution, which was believed to be responsible for the increasing diameters of HA nanofibers corresponding to higher DMF content. Controllable HA nanofibers with diameter below 100 nm have great promising for developing novel nanobiomaterials applied in tissue engineering and regenerative medicine.
纳米纤维普遍存在于各种人体组织的天然细胞外基质（ECM）中，形成水合交织网络。静电纺丝纳米技术已被证明是一种制造可模拟天然ECM结构的可控纳米纤维的强大技术。透明质酸（HA）作为天然ECM的关键成分，已广泛应用于组织工程和再生医学。在本研究中，使用不同的静电纺丝参数成功制备了平均直径为33±5nm、59±12nm、79±12nm和113±19nm的纯HA纳米纤维。首次详细研究了环境相对湿度对HA可纺性的影响，结果证明，除溶液性质外，环境相对湿度是控制HA纳米纤维形态的最重要因素之一。观察到特定HA溶液的湿度临界值，只有低于该临界值才能成功获得直径和形态相似的HA纳米纤维。当环境相对湿度高于临界值时，HA纳米纤维在交叉点开始溶解，甚至融合在一起形成扩散层。此外，发现仅需少量N，N-二甲基甲酰胺（DMF）与水混合作为溶剂即可提高HA溶液的可纺性。随着DMF含量增加，溶液表面张力显著降低，这被认为有利于静电纺丝中稳定的泰勒锥和流体射流的形成。同时，应注意溶液的电导率也随着溶液中DMF含量的增加而降低，这被认为是导致对应于较高DMF含量的HA纳米纤维直径增加的原因。直径低于100nm的可控HA纳米纤维在开发应用于组织工程和再生医学的新型纳米生物材料方面具有巨大潜力。
