Electrospinning and mechanical characterization of gelatin nanofibers Zheng-Ming Huang a, * , Y.Z. Zhang b,c , S. Ramakrishna b,c,d , C.T. Lim b,c,d a School of Aeronautics, Astronautics and Mechanics, Tongji University, 1239 Siping Road, Shanghai 200092, People’s Republic of China b Department of Mechanical Engineering, National University of Singapore, Singapore 117576, Singapore c Division of Bioengineering, National University of Singapore, Singapore 117576, Singapore d Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576, Singapore Received 23 January 2004; received in revised form 3 April 2004; accepted 3 April 2004 Available online 17 June 2004 Abstract This paper investigates electrospinning of a natural biopolymer, gelatin, and the mass concentration-mechanical property relationship of the resulting nanofiber membranes. It has been recognized that although gelatin can be easily dissolved in water the gelatin/water solution was unable to electrospin into ultra fine fibers. A different organic solvent, 2,2,2-trifluoroethanol, is proven suitable for gelatin, and the resulting solution with a mass concentration in between 5 and 12.5% can be successfully electrospun into nanofibers of a diameter in a range from 100 to 340 nm. Further lower or higher mass concentration was inapplicable in electrospinning at ambient conditions. We have found in this study that the highest mechanical behavior did not occur to the nanofibrous membrane electrospun from the lowest or the highest mass concentration solution. Instead, the nanofiber mat that had the finest fiber structure and no beads on surface obtained from the 7.5% mass concentration exhibited the largest tensile modulus and ultimate tensile strength, which are respectively 40 and 60% greater than those produced from the remaining mass concentration, i.e. 5, 10, and 12.5%, solutions. q 2004 Elsevier Ltd. All rights reserved. Keywords: Electrospinning; Gelatin; Nanofiber 1. Introduction Electrospinning technique has been recognized as an efficient processing method to manufacture nanoscale fibrous structures for a number of applications [1]. In biomedical field, for example, this technique can be used to make wound dressings [2,3], drug delivery platforms [4,5], tissue engineering scaffolds [6–8], and so forth. For tissue scaffold application, the fiber mats produced from biode- gradable polymers have a diameter ranging from several microns down to a few nanometers. Such small size fibers could physically mimic the structural dimension of the extracellular matrix of various native tissues and organs, which are deposited and proliferated on essentially fibrous structures realigning from nanometers to millimeters. As human cells can attach and organize well around fibers with diameters smaller than those of the cells [9], the fibrous scaffolds prepared from electrospinning can be considered as ideal candidates. So far, the majority of work related with electrospinning biodegradable polymers has been focused on synthetic materials, mostly on PLA, PGA, PLGA, and PCL. For many biomedical applications, the most important characteristics that should be targeted for include biocompatibility and mechanical performance. In comparison with synthetic counterparts, natural biopolymers generally have better biocompatibility and hence are more suitable for human body. However, to convert a natural biopolymer into submicron or nanometer fibers through electrospinning is usually more difficult than to do a synthetic polymer. Due to this reason, only in the recent literature have we found a few reports addressing electrospinning of some natural biopo- lymers [3,6,10]. In this paper, we investigate electrospinning of a different biopolymer, gelatin material, not done yet in the literature. Gelatin is a natural biopolymer derived from collagens and has almost identical compositions and biological properties as those of collagens. It is an aqueous polymer, i.e. dissolvable in water. Unfortunately, gelatin/water system 0032-3861/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2004.04.005 Polymer 45 (2004) 5361–5368 www.elsevier.com/locate/polymer * Corresponding author. Tel.: þ 86-21-65985373; fax: þ 86-21- 65982914. E-mail address: huangzm@mail.tongji.edu.cn (Z.M. Huang).