For several reasons, the electrospinning of nanofibrous mats comprised purely of biopolymers, such as hyaluronic acid (HA) has been difficult to achieve. Most notably, due to its polyelectrolytic nature, very low polymer concentrations exhibit very high solution viscosities. Thus, it is challenging to obtain the critical chain entanglement concentration necessary for biopolymer electrospinning to ensue. While the successful electrospinning of HA fibers from a sodium hydroxide:dimethylformamide (NaOH:DMF) system has been reported, the diameter of these fibers was well above 100 nm. Moreover, questions regarding the degradation of HA within the solvent system arose. These factors supported our ongoing research into determining an improved solvent system. In this study, the use of a less basic (pH 11) aqueous ammonium hydroxide (NH(4)OH) solvent system. NH(4)OH:DMF, allowed for the fabrication of HA mats having an average fiber diameter of 39 +/- 12 nm. Importantly, while using this solvent system, no degradation effects were observed and the continuous electrospinning of pure HA fibers was possible. (C) 2011 Elsevier Ltd. All rights reserved.