Carbohydrate Polymers 88 (2012) 1023–1032 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers jo u rn al hom epa ge: www.elsevier.com/locate/carbpol Oxidized regenerated cellulose-based hemostat with microscopically gradient structure Yadong Wu a,1 , Jinmei He a,1 , Weilu Cheng a,1 , Hongbo Gu a,b,1 , Zhanhu Guo b,1 , Shan Gao c,1 , Yudong Huang a,∗,1 a School of Chemical Engineering and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, China b Integrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, TX 77710, USA c WeGo Group, Weihai 264209, China a r t i c l e i n f o Article history: Received 3 November 2011 Received in revised form 24 December 2011 Accepted 18 January 2012 Available online 25 January 2012 Keywords: Oxidized regenerated cellulose Controlled neutralization Oxidized regenerated cellulose sodium Hemostatic Biodegradability a b s t r a c t Partially water-soluble oxidized regenerated cellulose carboxylate sodium (ORC-Na) materials have been prepared by controlled neutralizing oxidized generated cellulose (ORC). The carboxyl were converted into sodium carboxylate as evidenced by FT-IR, and carboxyl content decreased from 18.41% to 0.98%, with enhancing water solubility of ORC-Na to form gel, and SEM–EDX revealed that the sodium carboxylate groups presented in a gradient distribution from the exterior to the interior of fiber. ORC-Na introduced a new hemostatic mechanism, i.e., forming gel to mechanically seal off the crevasses of vessels. Due to its excellent water solubility and 5.23% carboxyl, ORC-Na-3 possessed optimum hemostatic efficiency and demonstrated a capability to stop bleeding within shortest time (102 and 138 s) with the least blood loss (0.886 and 1.006 g), and implantation test showed ORC-Na-3 could be absorbed in less than 2 weeks with no pathological response remaining. In conclusion, ORC-Na-3 is an efficient hemostat with optimum biodegradability. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Oxidized regenerated cellulose, which could be obtained by partial oxidation of the primary hydroxyl groups on the anhy- droglucose rings to produce the monocarboxyl cellulose, is a kind of natural and topical biomaterials. Within the range of 16–24% car- boxylic acid content, all the ORC materials represent an important class of biocompatible and bioabsorbable polymers, and they have been available in a sterilized knitted fabric or powder form for use in human beings to stop bleeding (Zhu, Kumar, & Banker, 2001), which have been proved to hold an excellent bio-security. ORC was prepared and studied for the first time in the late 1930s. Nitrogen dioxide (Camy, Montanari, Rattaz, Vignon, & Condoret, 2009; Foglarova, Prokop, & Milichovsky, 2009; Yackel & Kenyon, 1941; Zimnitsky, Yurkshtovich, & Bychkovsky, 2004), the initial kind of oxidants, which was used for the selective oxidation of the primary hydroxyl groups in the cellulose, was reported in the 1940s. So far, both gaseous and liquid nitrogen dioxide oxidation ∗ Corresponding author at: School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001, China. Tel.: +86 451 86414806; fax: +86 451 86403379/86414806. E-mail address: ydhuang.hit1@yahoo.com.cn (Y. Huang). 1 These authors contributed equally to this work. processes have been commercialized for many years. Recently, the preparation (Praskalo et al., 2009; Saito, Okita, Nge, Sugiyama, & Isogai, 2006; Yin, Koschella, & Heinze, 2009) and modification (Zhu et al., 2001; Zimnitsky, Yurkshtovich, & Bychkovsky, 2006) for oxi- dized generated cellulose are still of significant interest. Johnson & Johnson has pioneered an industrial scale oxidation process using nitrogen dioxide to manufacture ORC absorbable haemostat (Domb, Kost, & Wiseman, 1998) – Surgicel (Alpaslan, Alpaslan, & Oygur, 1997; Ashworth & Whear, 2003; Breech & Laufer, 2000; Loescher & Robinson, 1998; Sharma & Malhotra, 2006; Sharma, Malhotra, & Pundir, 2003). In recent decades, commercial Surgicel absorbable hemostatic agent has been widely applied in various surgeries and played an important role on stopping the bleeding. Although this hemostatic material is broadly applied due to its excellent properties, the commercial ORC has also shown several inherent disadvantages. For example, the hemostatic property of this material is relatively poor and has a low biodegradability. With a carboxyl content ranging from 16% to 24% and a pH approxi- mately of 3.1, ORC would damage nervous system if this material is implanted in the human body. Many researchers have made great efforts to improve the hemostatic performance and to overcome other shortcomings (Watt, Harvey, & Wiseman, 2003), but signif- icant improvement on the hemostatic performance is still limited (Harvey, Leeuwen, Hyland, & Aitken, 2001). Stilwell et al. reported 0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2012.01.058