Fabrication of a Cellulose-Based Nanocomposite as a Potential Scaffold in Tissue Engineering

Amanda Williams, University of South Carolina, 2012 SURF Fellow Advisor: Prof. Hamid Garmestani Graduate Mentor: Parisa Pooyan Introduction Many biopolymers in place today lack native biomechanical characteristics of the target tissue and are mechanically and thermally unstable. A suggested material to combat these issues is a composite material made of a biopolymer matrix with a reinforcing agent. Natural fibers are desired as the reinforcing agent for their biocompatibility, renewability, abundance, and petroleum-free, energy efficient production methods. 2 Cellulose nanowhiskers (CNW) are ideal due to their highly variable nature, modification potential, biodegradability properties, minimal immune-inductive effects, and stability after mechanical testing, sterilization, and aging. 4, 5, 6, 7 CNW have many of cellulose’s key properties while incorporating properties of nanowhiskers. The high specific surface area of CNW could lead to better interactions between the CNW and matrix as well as improve the material’s mechanical properties. Cellulose acetate propionate (CAP) is the natural biopolymer matrix that the CNW will reinforce. A natural matrix is preferred over synthetics to increase the composite material’s biocompatibility, and there has been evidence of low interfacial stability between synthetic matrices and natural fibers, like the CNW in this experiment. CAP already has applications in the biomedical field, such as drug coatings and applications requiring selective protein absorption due heavily to its biocompatibility. As a derivative of cellulose acetate (CA), CAP membranes are porous, highly compatible with solvents, chemically stable, and easily accessible commercially. Both CAP and CA are cellulose esters. Cellulose esters are widely accepted biopolymers that have uses in LCD flat screens, yarn, separation techniques in water usage, and medical separation techniques. 10, 11 Significantly, when cellulose esters are combined with natural fibers, such as the CNW, they exhibit good biocompatibility and biodegradability. Experimental Methods CNW can be isolated from different sources, which can produce different sized nanowhiskers. In this experiment, they were isolated from cotton. Nanowhiskers are abundant in cotton and have approximately 90% crystallinity when isolated from cotton. An aqueous suspension of nanowhiskers were isolated by acid hydrolysis of microcrystalline cellulose. 12 Then these nanowhiskers were dispersed in the CAP mixture. The composite solution was allowed to set at room temperature in a mold to form a thin film which became the composite material. Two material characterization tests were performed: a tensile test and x-ray diffraction (XRD).