In our previous study, two types of collagen nanofibers were successfully prepared by the aqueous counter collision (ACC) method, which can selectively cleave intermolecular interactions engaged in native collagen micro-fibrils. There was a question still remained whether i) the two collagen nanofibers limited to be prepared by ACC or not, and ii) the two collagen nanofibers are only the building blocks for native collagen micro-fibrils or not. Therefore, the current study employed "Sequential ACC process" for more efficient downsizing of native collagen micro-fibrils, and eventually found presence of a thinner building block. It exhibited a rod-like shape termed as "Collagen nano-block (CN-Block)" and had ca.220 MPa of tensile strength that is a value between the two of collagen nanofibers. Although both the zeta potential value and elemental composition of CN-Block were similar to the collagen nanofibers, they had different degree of interactions among collagen supramolecules in the lateral directions based on wide angle X-ray diffraction measurements. According to viscosity measurements, surfaces of the CN-Block exhibited less water absorptivity than the two nanofibers. Namely, CN-Block was more hydrophobic on the surface than other ones.
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