Plant-Derived Nanocellulose as Structural and Mechanical Reinforcement of Freeze-Cast Chitosan Scaffolds for Biomedical Applications
Year: 2019
Type: article
Abstract: Despite considerable recent interest in micro- and nanofibrillated cellulose as constituents of lightweight structures and scaffolds for applications that range from thermal insulation to filtration, few systematic studies have been reported to date on structure-property-processing correlations in freeze-cast chitosan-nanocellulose composite scaffolds, in general, and their application in tissue regeneration, in particular. Reported in this study are the effects of the addition of plant-derived nanocellulose fibrils (CNF), crystals (CNCs), or a blend of the two (CNB) to the biopolymer chitosan on the structure and properties of the resulting composites. Chitosan-nanocellulose composite scaffolds were freeze-cast at 10 and 1 °C/min, and their microstructures were quantified in both the dry and fully hydrated states using scanning electron and confocal microscopy, respectively. The modulus, yield strength, and toughness (work to 60% strain) were determined in compression parallel and the modulus also perpendicular to the freezing direction to quantify anisotropy. Observed were the preferential alignments of CNCs and/or fibrils parallel to the freezing direction. Additionally, observed was the self-assembly of the nanocellulose into microstruts and microbridges between adjacent cell walls (lamellae), features that affected the mechanical properties of the scaffolds. When freeze-cast at 1 °C/min, chitosan-CNF scaffolds had the highest modulus, yield strength, toughness, and smallest anisotropy ratio, followed by chitosan and the composites made with the nanocellulose blend, and that with crystalline cellulose. These results illustrate that the nanocellulose additions homogenize the mechanical properties of the scaffold through cell-wall material self-assembly, on the one hand, and add architectural features such as bridges and pillars, on the other. The latter transfer loads and enable the scaffolds to resist deformation also perpendicular to the freezing direction. The observed property profile and the materials' proven biocompatibility highlight the promise of chitosan-nanocellulose composites for a large range of applications, including those for biomedical implants and devices.
Source: Biomacromolecules
Institution: Dartmouth College
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funders: National Aeronautics and Space Administration, National Institutes of Health, National Cancer Institute, National Institute of Child Health and Human Development, Division of Civil, Mechanical and Manufacturing Innovation, Eunice Kennedy Shriver National Institute of Child Health and Human Development
Awards: A Nanotherapeutic Device for Effective Non-Surgical Female Sterilization, DARTMOUTH S CONTRIBUTION TO THE TEAM EFFORT OF THE COLLABORATIVE NASA PROJECT ENTITLED STRUCTURE-PROPERTY-PROCESSING CORRELATIONS IN FREEZE-CAST BIOMIMETIC MATERIALS WILL BE TO INVESTIGATE AND DETERMINE WITH CUSTOM-DESIGNED FREEZING STAGES ANALYTICAL TOOLS AND CONTRIBUTIONS TO THE MODELING EFFORT THE KINETICS OF THE ICE-PHASE GROWTH AND THE MECHANISMS BY WHICH THE GROWING ICE-CRYSTALS THUS ICE PHASE TEMPLATES THE POLYMER PHASE DURING ITS TRANSITION FROM A SOLUTION TO A GLASSY SOLID. THE WATER-BASED SYSTEM WILL BE COMPARED WITH MODEL SYSTEMS SUCH AS THAT OF TBA-WATER: (I) WITH LIGHT MICROSCOPY PERPENDICULAR TO THE MOVING FREEZING FRONT WE WISH TO OBSERVE THE FORMATION OF MULLINS- SEKERKA INSTABILITIES AND THEIR SUBSEQUENT REORGANIZATION INTO AN ARRAY OF CELLS OR DENDRITES AS A FUNCTION OF POLYMER CONCENTRATION AND COOLING RATES WHICH IS EQUAL TO THE PRODUCT OF VELOCITY AND THERMAL GRADIENT IN DIRECTIONAL SOLIDIFICATION; (II) WITH CONFOCAL MICROSCOPY PARALLEL TO THE FREEZING FRONT WE WISH TO OBSERVE AND DETERMINE UNDER WHICH EXACT PROCESSING CONDITIONS SUCH AS POLYMER CONCENTRATION AND COOLING RATE THE DIFFERENT STRUCTURES FORM ON EARTH IN PREPARATION OF EXPERIMENTS USING THE REFURBISHED PFMI IN SPACE. FINALLY THE RESULTS OF THE EXPERIMENTAL AND THEORETICAL WORK WILL BE TRANSLATED INTO STRUCTURE-PROPERTY-PROCESSING CORRELATIONS FOR HIGHLY POROUS FREEZE-CAST MATERIALS (POLYMER CERAMIC METAL AND COMPOSITE) MADE ON EARTH SO THAT THEY CAN BE APPLIED IN THE DEVELOPMENT OF NEW AND IMPROVED FREEZE-CAST MATERIALS THAT ARE STRONG TOUGH AND LIGHTWEIGHT AND CAN BE CUSTOM-DESIGNED FOR A GIVEN APPLICATION. THE WORK EFFORT WILL PARALLEL THE FUNDING AND PHASE IN DURING YEARS 1 AND 2., G7854435144, Cancer Center Support Grant
OpenAlex ID: W2971264897