Abstract
Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.
Highlights
Composite materials of alginate and cellulose nanofibrils (CNF) have shown promising results for bioprinting and tissue engineering applications [1,2,3]
Resistance to to breakage breakage and and Composite gels of D. pot., M. pyr., and L. hyp. alginates and CNF saturated with calcium were measured with respect to gel rigidity (Young’s modulus) and deformation deformation at at breakage breakage was was determined determined (Figure oxidized) saturated with calcium were measured with respect to gel rigidity (Young’s modulus) and volume reduction upon gel formation
This is commonly seen for alginate oxidized) saturated with calcium were measured with respect to gel rigidity (Young’s modulus) and hydrogelsalso alsowhen whenusing using supercritical supercritical drying, totopreserve the structure in the hydrogels drying, intended intended preserve theoriginal original structure volume reduction upon gel formation
Summary
Composite materials of alginate and cellulose nanofibrils (CNF) have shown promising results for bioprinting and tissue engineering applications [1,2,3]. Alginate forms hydrogels by crosslinking with divalent cations where, the G-blocks, and the MG-blocks, are important for the mechanical properties of the resulting gel [5,6]. CNF hydrogels can be produced with cations, both monovalent and with higher valency [12], where gels with higher valency ions form stronger gels [12,13] Due to their availability, renewability, biocompatibility, and low toxicity, both alginate and cellulose are attractive materials for a range of applications such as films, gels, and as viscosifiers. Being suggested for tissue engineering applications, not much is known about the mechanical properties of composite gels of alginate and CNF. We hypothesize that by combining alginate and CNF, the advantageous properties of the individual constituents, i.e., the stiffness of CNF and the compressibility of alginate, could be preserved in the composite gel making it possible to tailor the mechanical properties
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