Preparation of Ultrafine Oxidized Cellulose Mats via Electrospinning Won Keun Son, § Ji Ho Youk, † and Won Ho Park* ,‡ Research Institute of Advanced Materials, Chungnam National University, Daejeon 305-764, South Korea, Department of Textile Engineering, College of Engineering, Inha University, Incheon, 402-751, South Korea, and Department of Textile Engineering, College of Engineering, Chungnam National University, Daejeon 305-764, South Korea Received August 21, 2003; Revised Manuscript Received September 25, 2003 Ultrafine oxidized cellulose (OC) mats were prepared by oxidation of ultrafine cellulose mats produced by electrospinning and subsequent deacetylation of cellulose acetate for potential applications in nonwoven adhesion barriers. When ultrafine cellulose mats were oxidized with a mixture of HNO 3 /H 3 PO 4 -NaNO 2 (2/1/1.4 v/v/wt %), their ultrafine mat structure remained unchanged. The yield and carboxyl content of OC mats were 86.7% and 16.8%, respectively. OC showed lower crystallinity than cellulose because the oxidation of cellulose proceeded via disruption of hydrogen bonds between cellulose chains. The swelling behaviors of ultrafine OC mats were dependent on the type of swelling solution. In a physiological salt solution, their degree of swelling was ∼230%. Introduction Oxidized cellulose (OC) is completely bioresorbable and readily degrades under physiological conditions. It is com- monly used in medical and related applications such as hemostats, bodying agents in cosmetic and pharmaceutical preparations, fibrin formation-accelerating agents, and adhe- sion barriers. 1-3 OC adhesion barriers in a fabric, liquid gellike solution, or membrane form have been used to reduce the formation of postsurgical adhesions especially after pelvic or abdominal surgery. These barriers also assist the healing process and are readily absorbed within a short period of time. For example, Interceed TC7 (Johnson and Johnson Medical Inc.), a fabric adhesion barrier made from oxidized regenerated cellulose, becomes a gel to form a protective coating within 8 h and is completely absorbed within 28 days. 4-6 On the other hand, in electrospinning, polymer solutions or melts are ejected from a millimeter size capillary and deposited as nonwoven fibrous mats on a template serving as the ground for the electric charges by applying a strong electrostatic force. 7-10 These polymer mats exhibit high surface area-to-volume ratio, which is essential for applica- tions such as separation membranes, scaffolds for tissue engineering, wound dressing materials, artificial blood ves- sels, and sensors. 11-20 It is expected that ultrafine OC mats produced by electrospinning would be more flexible and easier to handle than commercial adhesion barriers and extend their applications in immobilizing matrixes for various drugs, enzymes, and proteins. 2,21,22 However, it is impossible to directly prepare ultrafine OC mats via electrospinning of OC because of its poor solubility to organic solvents. Therefore, as an alternative method, they can be prepared by oxidizing ultrafine cellulose mats. In our previous study, 23 ultrafine cellulose mats were successfully prepared via electrospinning and subsequent deacetylation of cellulose acetate (CA). These cellulose mats can be oxidized with various oxidants such as gaseous oxygen, hydrogen peroxide, peracetic acid, nitrogen oxide (dinitrogen tetraoxide), and hypochlorous acid. 24 Recently, Kumar and Yang 21 prepared OC having various carboxyl contents in high yield by treating cellulose with a mixture of HNO 3 /H 3 PO 4 -NaNO 2 at room temperature. In this study, ultrafine OC mats were prepared by oxidizing ultrafine cellulose mats produced by electrospinning and subsequent deacetylation of CA with a mixture of HNO 3 / H 3 PO 4 -NaNO 2 , and their physical properties were investi- gated for potential applications in nonwoven adhesion barriers. Experimental Section Materials. CA (39.8%, acetyl content, MW ) 30 000) was purchased from Aldrich Co. and used without further purification. Acetone, KOH, NaNO 2 ,H 3 PO 4 (85%, w/v), HNO 3 (69.7%, w/v), and H 2 SO 4 (95%, w/v) were purchased from Duksan Chemical Co. HCl and NaOH aqueous solu- tions were 0.1 N standard solutions. Electrospinning. Figure 1 shows a schematic diagram of the electrospinning setup used in this study. 10 It consisted of a syringe and needle (i.d. ) 0.84 mm), a ground electrode (d ) 21.5 cm, stainless steel sheet on a drum the rotation speed of which can be varied), and a high-voltage supply (Chungpa EMT, CPS-40K03). The needle was connected to the high-voltage supply. The distance between the needle * Corresponding author. Tel: +82-42-821-6613. Fax: +82-42-823-3736. E-mail address: parkwh@cnu.ac.kr. § Research Institute of Advanced Materials, Chungnam National Uni- versity. † Inha University. ‡ College of Engineering, Chungnam National University. 197 Biomacromolecules 2004, 5, 197-201 10.1021/bm034312g CCC: $27.50 © 2004 American Chemical Society Published on Web 11/11/2003