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.