Preparation and characterization of chitosan-based nanofibers by ecofriendly electrospinning Yanan Liu a , Mira Park b , Hye Kyoung Shin c , Bishweshwar Pant a , Soo-Jin Park c,n , Hak-Yong Kim a,nn a Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756, South Korea b Department of Organic Materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756, South Korea c Department of Chemistry, Inha University,100 Inharo, Incheon 402-751, South Korea article info Article history: Received 27 December 2013 Accepted 7 June 2014 Available online 16 June 2014 Keywords: Electrospinning Chitosan Poly(vinyl alcohol) EBI Nanofibers abstract Cross-linked chitosan/poly(vinyl alcohol) (CS/PVA with weight ratios of 2:1, 1:1, 1:2 and 1:3) nanofibers have been successfully electrospun using 1% aqueous acetic acid. Viscosity average molecular weight of CS was reduced from 78.7  10 4 to 1.4  10 4 by electron beam irradiation (EBI) in order to improve its solubility. The effects of composition on morphologies and swelling property of electrospun nanofibers were investigated. Fourier transform infrared (FTIR) spectroscopy studies demonstrated main chemical structure of CS persisted after EBI treatment. Swelling behavior test after cross-linking confirmed that the non-toxic CS-based nanofibers have a potential application in the biomedical field. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Electrospinning is regarded as a well-known and versatile technique to fabricate micro and nanofibers with high porosity and surface area-to-volume ratio [1], and more importantly, morphological similarity to natural extracellular matrix. These architectural structural nanofibers are appropriate for biomaterials such as wound dressing, drug release, tissue engineering and so forth [2]. CS-based nanofibers have been identified as an excellent biomaterial, due to biodegradability, biocompatibility and anti- bacterial properties of CS [3]. Low solubility and stability of CS inhibit the electrospinnability of pure CS. Many methods such as alkalization, ultraviolet, gamma ray irradiation, and enzyme degra- dation have been utilized to improve the solubility [4,5]. Homayoni et al. [6] fabricated CS nanofibers from 90% CH 3 COOH solution after the hydrolysis of CS for 48 h. Recently, electrospun CS/PVA nanofibers have been successfully fabricated [7–9]. How- ever, electrospinning conditions are relatively limited in terms of concentration, molecular weight, and degree of deacetylation of CS. Some solvents such as trifluoroacetic acid, dichloromethane or acrylic acid are employed in the process, residual toxic solvent in electrospun products limits the applications in the biomedical field. Considering these aspects, it is an alternative approach to diminish molecular weight of polysaccharides by electron beam irradiation (EBI). The molecular weight of CS can be reduced without changing main structure under optimized conditions [10]. In this paper, CS was modified by EBI in order to dissolve completely in 1% aqueous CH 3 COOH. It provides a good way to get non-toxic and environmentally friendly system for electrospin- ning. Thus-obtained non-toxic CS-based nanofibers may become outstanding candidates for biomedical applications. 2. Experimental 8 wt% gelatinous CS (200,000 cps, the degree of deacetylation: 75–85%, Aldrich Co.) was made from 1% aqueous CH 3 COOH, and irradiated by EBI at a dose of 50 kGy. The irradiation was performed using an electron beam accelerator (beam energy of 2.5 MeV, beam current of 8.5 mA, conveyor velocity of 10 m/min, dose rate of 6.67 kGy/s, EBTECH Co., Ltd., Korea) at room tempera- ture in an air atmosphere. 10 wt% PVA (M w ¼ 85,000–124,000, Aldrich Co.) and CS solutions were mixed with different weight ratios (3:1, 2:1, 1:1, and 1:2). Glyoxal solution (40wt% in H 2 O, Aldrich Co.) was added as a cross-linker (6 wt% with weight of PVA). The solution was electrospun at 18 kV by maintaining a tip-to-collector distance of 16 cm. A schematic diagram of the electrospinning process is shown in Fig. 1(A). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2014.06.041 0167-577X/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ82 32 876 7234; fax: þ82 32 867 5604. nn Corresponding author. Tel.: þ82 63 270 2351; fax: þ82 63 270 4249. E-mail addresses: sjpark@inha.ac.kr (S.-J. Park), khy@jbnu.ac.kr (H.-Y. Kim). Materials Letters 132 (2014) 23–26