Biomaterials 26 (2005) 6176–6184 Electrospun chitosan-based nanofibers and their cellular compatibility Narayan Bhattarai a , Dennis Edmondson a , Omid Veiseh a , Frederick A. Matsen b , Miqin Zhang a,b,Ã a Department of Materials Science & Engineering, University of Washington, Seattle, WA 98195-2120, USA b Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA 98195-6500, USA Received 4 January 2005; accepted 23 March 2005 Available online 10 May 2005 Abstract Chitosan-based nanofibers with an average fiber diameter controllable from a few microns down to 40 nm and a narrow size distribution were fabricated by electrospinning solutions containing chitosan, polyethylene oxide (PEO), and Triton X-100 TM . Rheological study showed a strong dependence of spinnability and fiber morphology on solution viscosity and thus on chitosan-to- PEO ratio. The nanofibers can be deposited either as a nonwoven mat or as a highly aligned bundle of controllable size. Potential use of this nanofibrous matrix for tissue engineering was studied by examining its integrity in water and cellular compatibility. It was found that the matrix with a chitosan/PEO ratio of 90/10 retained excellent integrity of the fibrous structure in water. Experimental results from cell stain assay and SEM imaging showed that the nanofibrous structure promoted the attachment of human osteoblasts and chondrocytes and maintained characteristic cell morphology and viability throughout the period of study. This nanofibrous matrix is of particular interest in tissue engineering for controlled drug release and tissue remodeling. r 2005 Elsevier Ltd. All rights reserved. Keywords: Chitosan; Nanofiber; Electrospinning; Biodegradable; Scaffold 1. Introduction Polymeric nanofibers that mimic the structure and function of the natural extracellular matrix (ECM) are of great interest in tissue engineering as scaffolding materials to restore, maintain or improve the function of human tissues. The natural ECMs in the body are mainly composed of two classes of extracellular macro- molecules: proteoglycans and fibrous proteins with fiber diameters ranging from 50 to 150nm, depending on tissue type [1,2]. Studies showed that the material size feature can substantially influence the morphology and function of cells grown on the ECM, and that cells attach and proliferate well in micro and nanostructured materials [3,4]. A number of manufacturing processes have been explored to fabricate micro or nanoscale fibrous matrices, including drawing [5], self-assembly [6], template-directed synthesis [7], phase separation [8], and electrospinning [9–12]. Among these techniques, the electrospinning has been widely accepted as the simplest and least expensive means to fabricate ultrafine fibers, and has been employed to fabricate nanofibers from a variety of synthetic or natural polymers [5]. Natural polymers are generally favored over synthetic polymers in tissue engineering in view of their proven tissue compatibility and resorbable biodegradation products. Collagen and chitosan are two naturally derived polymers that are most commonly used in tissue engineering [13]. Collagen has been used to fabricate nanofibers with diameters in the range of 100 nm to a ARTICLE IN PRESS www.elsevier.com/locate/biomaterials 0142-9612/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2005.03.027 Ã Corresponding author. Department of Materials Science & Engineering, University of Washington, Seattle, WA 98195-2120, USA. Tel.: +12066169356; fax: +12065433100. E-mail address: mzhang@u.washington.edu (M. Zhang).