Robust adhesion between solid-state hydroxyapatite and bone tissue through surface demineralization.

Xie, Shichao; Okada, Masahiro; Aoyagi, Haruyuki; Otaka, Akihisa; Yang, Xiaofeng; Nakano, Takayoshi; Matsumoto, Takuya · Bioact Mater · 2026

basic_science · Level V

Where this comes from

Abstract

Current bone adhesives typically lack adequate mechanical strength, long-term stability, or biocompatibility. To address these limitations, we designed a new adhesion strategy using a solid-state hydroxyapatite (HAp) adhesive in combination with bone surface demineralization. Solid-state HAp adhesives were synthesized via wet chemical precipitation and heat treatment. Cortical bone specimens were partially demineralized with phosphoric acid (H<sub>3</sub>PO<sub>4</sub>) or ethylenediaminetetraacetic acid (EDTA), and characterized using scanning electron microscopy (SEM) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Shear adhesion strength of HAp to demineralized bone was measured over time. <i>In vivo</i> fixation was assessed in rats using micro-computed tomography and histology. Statistical analysis used Tukey-Kramer tests after normality and variance checks. Although the HAp adhesive failed to adhere to non-demineralized bone, effective adhesion was achieved on the surface-demineralized bone tissue. Shear adhesion strength was significantly higher in EDTA-treated samples (238.4 kPa at 10 h) compared to H<sub>3</sub>PO<sub>4</sub>-treated samples (102.9 kPa at 1 h), with performance correlating with demineralization depth. ATR-FTIR and SEM analyses revealed that EDTA preserved collagen's triple-helix structure and free water content, both enhancing adhesion. Animal experiments confirmed stable fixation of HAp adhesive to demineralized bone tissue. Surface demineralization enabled strong adhesion of the solid-state HAp adhesive to bone by exposing collagen swollen with water. Adhesion strength was influenced by structural changes in the demineralized layer, and the adhesive provided stable <i>in vivo</i> fixation, supporting its potential for bone-anchored biomedical applications.