Green efficient ultrasonic-assisted extraction of abalone nacre water-soluble organic matrix for bioinspired enamel remineralization

Reconstructing enamel-like hydroxyapatite structures on damaged teeth remains a great challenge in the materials science and dentistry due to its highly ordered hierarchical microstructure. Inspired by the mineralization of mollusk nacre in nature, abalone nacre water-soluble organic matrix (WSM) was isolated successfully though an ultrasonic-assisted water extraction (UWE) strategy with nondestructive activity and high-quality extraction for simulating the process of tooth hard tissue mineralization. Results showed that the UWE strategy significantly increased the protein yield from 7.60% to 9.60% and improved the polysaccharide yield from 2.59% to 3.34%, respectively, indicating its excellent extraction efficiency of WSM. Noteworthily, the smallest averaged particle size (~155 nm) of WSM were obtained at an ultrasound time of 6 h, whereas the highest absolute values (~ -32 mV) of zeta potential was produced. Moreover, it was proved that WSM could induce the growth of enamel-like hydroxyapatite crystals to further facilitate biomimetic remineralization of the demineralized enamel and restore its continuous and smooth surface structure in vitro. Besides, the hardness (4.37 ± 0.07 GPa) and modulus of elasticity (84.80 ± 1.49 GPa) of the WSM-repaired enamel was similar to that of native enamel, indicating superior mechanical properties after repair. Herein, it provides a promising green, efficient strategy for the remineralization of damaged enamel and high value utilization of waste abalone shells.