Development of Bacterial Cellulose Nanocomposites
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Development of Bacterial Cellulose Nanocomposites Roberto Benson1, Hugh M. O’Neill2, B.R. Evans2, S. Hutchens1, C.P. Stephens3, and R. Hammonds1 1 Materials Science and Engineering, University of Tennessee-Knoxville, Knoxville, TN 2 Oak Ridge National Laboratories, Oak Ridge, TN 3 Department of Surgery, Graduate School of Medicine, Knoxville, TN
ABSTRACT The development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment. 1. INTRODUCTION 1a. Overall objective The ideal synthetic material for bone replacement to treat the effects of disease, traumatic injury, and non-unions remains a major concern in biomaterials science and engineering. The drive for using a biomimetic synthetic material over a biologically derived material is that it negates the possibility of disease transmission and adverse immunogenic response. A number of potentially favorable biocompatible materials (ceramics and filled polymers) have been developed and used as bone replacement materials [1-3]. Some clinically used ceramic materials include Bioglass, ȕ- tricalcium phosphate (ȕ-TCP), hydroxyapatite (HA), and biphasic calcium phosphate (BCP, which is a mixture of ȕ-TCP and HA). These ceramics have been shown to support osteoblast adhesion and growth. However, one of the primary drawbacks of utilizing a purely ceramic bone filler/replacement is its inherent brittleness. Creating a polymer-ceramic composite can reduce the brittleness that is characteristic of a purely ceramic scaffold. Thus the composite approach seems appropriate and even biomimetic since natural bone is a composite consisting of 25% water, 15% organic materials, and 60% mineral phase (by weight) [4]. This report will focus on efforts currently underway to develop such a bioactive polymer-ceramic composite. 1b. Development of the polymeric composite matrix The first component of the composite that must be developed is a nano-fibrous polymeric scaffold that mimics the natural collagen in bone. In vivo, collagen type I makes up 90% of the organic mass in bone [5]. Collagen forms a hierarchical structure starting with the fibril that has a diameter of 1 nm, a fibrillar structure composed of triple helical collagen molecules with a diameter of 100-200 nm and then further organizes into larger lamellar fiber bundles [6, 7]. Our collagen simulant is compose
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