pH‐responsive variation of biomineralization via collagen self‐assembly and the simultaneous formation of apatite minerals

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Abstract
Collagen self‐assembly and simultaneous mineralization by incubating a mixture containing collagen, calcium, and phosphate ions under physiological conditions, is an effective method to prepare bone‐like biomimetic materials. The formation of fibrils and minerals is related to pH of system. In the present work, we evaluated the effect of pH (7.9–10.4) on biomineralization process and synthesized composites. Turbidity kinetics and X‐ray diffraction (XRD) measurements revealed that increasing pH delayed the crystallization process from nucleation phase to plateau phase because of promoting chelation of Ca2+ with collagen. Typical peaks of phosphate in Fourier transform infrared spectroscopy coupling with characteristic peaks of hydroxyapatite (HAp) in XRD spectra illustrated the formation of HAp after biomineralization. Scanning electron microscopy measurements indicated that the increase of pH promoted the deposition of spherical minerals in fibrils. Especially, the minerals tended to form cluster‐like structure at pH 10.4. The hyp content, Ca and P contents, and gel strength measurements suggested that higher pH promoted the formation of HAp with a Ca/P closed to 1.67 and the prolongation of crystallization gave the time for collagen self‐assembly leading to the increase of gel strength at higher pH (9.4–10.4). These results might provide some new ideas for designing biomimetic materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48876.

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