Biocompatibility of hydroxyapatite/collagen paste with 3-glycidoxypropyltrimethoxysilane

摘要

Self-setting paste type artificial bones with biodegradability or bioresorbability are strongly desired by surgeons due to their natures to be utilized for filling them into complicated shapes of bone defects easily and for minimal invasive surgery, and to be disappeared to ignore side-effects by remaining of the paste. A hydroxyapatite/collagen bone like nanocomposite (HAp/Col), which is incorporated into bone remodeling process, has been clinically applied in Japan as biodegradable bone filler in porous body; however, HAp/Col self-setting pastes are not yet reported as enough properties to be applied. In this study, 3-glycidoxypropyltrimethoxysilane (GPTMS) aqueous solution, which works as a cross-linker of collagen via amino groups, was mixed with the HAp/Col powder to prepare HAp/Col self-setting bone pastes, and their physical properties and biocompatibility of the HAp/Col self-setting paste were investigated. The HAp/Col at the hydroxyapatite and collagen mass ratio of 80:20 was synthesized by the simultaneous titration method. The HAp/Col powder, a powder phase of HAp/Col self-setting bone pastes, was prepared by a uniaxial compacting dehydration, freeze-drying, crushing and classifying to 100 μm or less in grain size. Liquid phase of the pastes was GPTMS aqueous solution of 1 % in volume at just 1 h after mixing of GPTMS with pure water to hydrolyze GPTMS. The powder/liquid (P/L) ratios of the pastes were ranging from 0.33 to 1.50 g/cm~3. A compressive strength of the paste was measured according to the Japanese industrial standard JIS T 03304. In brief, the raw materials were mixed and filled in cylindrical shape Teflon~® mold. The mold was then sealed up and was soaked in distilled water of 37 °C for 72 h just after incubating for 1 h in 37 °C, 100 % relatively humidity After the soaking, the compressive strength of the paste was measured with autograph (AGS 5kN, Shimadzu, Japan) at a cross-head speed of 0.5 mm/min. The biocompatibility of the HAp/Col paste was investigated by a cell culture test using human osteoblast-like cell line, MG63. The results of compressive strength test for the HAp/Col pastes are shown in Fig. 1. The compressive strength of the paste was increased with increasing in the P/L ratio, i.e., increasing of the HAp/Col powder amount. The compressive strength of the paste was affected dominantly by increasing in the paste density rather than cross-link between GPTMS and collagen and formation of siloxane network. The Young's modulus of the paste also increased with increasing in the P/L ratio as shown in Table 1. Even the highest Young's modulus of 4.14 MPa is lower than the general bone cement and cortical bone. However, the pastes showed viscoelasticity and could viscoelastically deform without fracture. The HAp/Col-GPTMS paste at P/L ratio of 1.00, the paste showed cytocompatibility to MG63 cells. Details will be presented on podium. The HAp/Col-GPTMS paste could be good candidate for biocompatible bone paste with viscoelasticity.