Preparation and characterization of two types of separate collagen nanofibers with different widths using aqueous counter collision as a gentle top-down process

Two types of single collagen nanofibers with different widths were successfully prepared from native collagen fibrils using aqueous counter collision (ACC) as a top-down process. A mild collision of an aqueous suspension at a 100 MPa ejection pressure yielded nanofibers, termed CNF100, which have an inherent axial periodicity and are ∼100 nm in width and ∼10 μm in length. In contrast, ACC treatment at 200 MPa provided a non-periodic, shorter and thinner nanofiber, termed CNF10, that was ∼10 nm in width and ∼5 μm in length. Both nanofibers exhibited the inherent triple helix conformation of native collagen supramolecules. Even a medial collision that exceeded the above ACC pressures provided solely a mixture of the two nanofiber products. The two nanofiber types were well characterized, and their tensile strengths were estimated based on their sonication-induced fragmentation behaviors that related to their individual fiber morphologies. As a result, CNF10, which was found to be a critical minimum nanofibril unit, and CNF10 exhibited totally different features in sizes, morphology, tensile strength and viscoelastic properties. In particular, as the mechanical strength of the molecular scaffold affects cell differentiation, the two collagen nanofibers prepared here by ACC have the potential for controlling cell differentiation in possibly different ways, as they have different mechanical properties. This encourages the consideration of the application of CNF100 and CNF10 in the fabrication of new functional materials with unique properties such as a scaffold for tissue engineering.