The Effect of Cellulose Nanofibres on Mechanical Properties and Bioactivity of Natural Polymers
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The Effect of Cellulose Nanofibres on Mechanical Properties and Bioactivity of Natural Polymers Ali Negahi Shirazi, Ali Fathi and Fariba Dehghani School of Chemical & Biomolecular Engineering, The University of Sydney, NSW 2006, Australia.
ABSTRACT Natural polymers, used for hydrogel fabrication, are generally bioactive and provide good environment for cell growth and proliferation. However, these polymers have low mechanical strength. Several approaches have been attempted to improve their mechanical properties such as fabrication of interpenetrating polymer network (IPN) and semi-IPN hydrogels, and also addition of a nano sized fibers or nano-particles. The aim of this study was to investigate the feasibility of using naturally derived nano-fillers such as cellulose nanocrystallines to enhance the mechanical properties of hydrogels. Gelatin methacrylate (GelMA) was used as a protein model for preparation of photo-crosslinked hydrogel. The effects of concentrations of photo initiator and cellulose nanocrystallines (CNC) on the characteristics of hydrogels were examined. In vitro studies showed negligible cytotoxic effect of CNC on human osteosarcoma cell growth when using less than 20 mg/ml CNC. Therefore, it is viable to use this nano-filler for biomedical applications. It was found that the compression modulus of gelatin hydrogel was increased 1.5 fold by addition of 10 mg/ml of CNC. These results demonstrate the high potential of using CNC for tissue engineering applications to enhance the mechanical strength of hydrogels. INTRODUCTION Gelatin is an irreversibly hydrated form of collagen broadly used in tissue engineering [1]. This biocompatible hydrogel possesses poor mechanical properties in physically crosslinked form. Chemically crosslinking of gelatin enhanced its mechanical performances. The cytotoxic nature of these crosslinking agent, however, restricts their biomedical application [2] Functionalization of amine-containing side groups of gelatin upon methacrylate groups resulted to a light crosslinkable hydrogel [3]. This stable hydrogel showed an improved mechanical performance in comparison with physically crosslinked gelatin [3]. Even though photocrosslinking is a rapid technique to fabricate gelatin methacrylate (GelMA) hydrogels, the mechanical properties of these hydrogels are relatively poor. Therefore, incorporation of reinforcing materials to GelMA hydrogels is inevitable. For instance, incorporation of 5 mg/ml silk to GelMA hydrogel significantly improved the compression modulus of hydrogel fivefold [4]. However, the inflammatory responses of silk might limit its applications as a reinforcing material. To overwhelm this drawback, the low immunoresponsive materials such as cellulose can be used as a reinforcement agent [5, 6]. Cellulose nanocrystallines (CNC) synthesized upon acid hydrolysis of cellulose had a modulus around 100 GPa [7]. The purpose of this study is to investigate the feasibility of using CNC as a cost effective reinforcing agent for improving the mechanical performance of hydr
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