Oriented/dual-gradient in structure and mechanics chitosan hydrogel bio-films based on stretching for guiding cell orientation

Various anisotropic scaffolds have been fabricated to significantly assist cell alignment or orientation to mimic the natural oriented tissues. To pursuit facile preparation and further exploration, the oriented hydrogel film was manufactured here through stretching-drying method by using high tensile strength chitosan hydrogel film, which could be effectively prepared after at least 3 h drying for 65% strain or 4 h drying for 35% strain. Furthermore, the chitosan hydrogel film with gradient nanofibrous structure and mechanical property was prepared via stretching-inclining-drying way which was newly proposed on the base of stretching-drying method. The gradient hydrogel film not only achieved random-to-aligned hierarchical nanofibrous structure, but also engendered obvious gradient mechanical performance, presenting the variable tensile modulus with a range from about 1 to 22 MPa after 8 h drying. This kind of random-to-aligned gradient structure can even adjust cell directions from random to orientation. Chitosan gradient hydrogel film shows a great promise in inducing cell migration, orientation and differentiation, especially as a powerful bio-scaffold for interface tissue engineering and regenerative medicine.