From collagen–chitosan blends to three-dimensional scaffolds: The influences of chitosan on collagen nanofibrillar structure and mechanical property

The nanofibrillar feature of native type I collagen is of great importance in maintaining its functions in vivo. In the field of engineering collagen-based materials in vitro, different fabrications may yield differences in collagen organization and thus affect the nanofibrous structure. Two approaches of fabricating collagen–chitosan (Col–Chi) scaffolds were presented in this study to investigate the respective impacts especially on nanostructures. Compared with glutaraldehyde cross-linking fabrications, thermally triggered cofibrillogenesis showed a preferred capability in fabricating favorable porous scaffolds and preserving uniform and orderly assembled nanofibrils. A detailed kinetic study of the cofibrillogenesis in thermally triggered approach was then carried out to reveal the possible factors affecting the final fibrillar structures. Zeta potential measurements in different Col–Chi blends with varying Chi/Col ratios indicated the influences of electrostatic interactions on the subsequent cofibrillogenesis process. The native D-periodicity of ∼64 nm was found on collagen fibrils in the presence of different amounts of chitosan by atomic force microscopy observation. The relevance of nanofibrillar structures to the overall performances of Col–Chi scaffolds was also revealed by assessing swelling behaviors and tensile measurements. The maximum tensile strength obtained in the thermally triggered scaffolds was up to ∼361.2 ± 32.3 kPa, emphasizing the significance of preserving biomimetic nanofibrillar structures in reconstruction of Col–Chi scaffolds.