# Optimization of Calcined Bone Powder and Silane-Crosslinked Alginate Composites for Enhanced Mechanical Performance as a Cortical Bone Substitute

## TL;DR

Researchers improved a bone substitute material to better mimic the strength of cortical bone by optimizing its composition and using nanoparticulated bone powder.

## Contribution

A novel strategy combining blending optimization and nanoparticulation to enhance mechanical properties of bone composites.

## Key findings

- Increasing alginate ratio and reducing silane agent improved mechanical properties significantly.
- Nanoparticulated bone powder further enhanced modulus, strength, and energy by 2.4x, 1.7x, and 1.4x respectively.
- Overall mechanical properties improved 8.4x to 18x, approaching those of cortical bone.

## Abstract

Developing bone substitute materials that mimic both trabecular and cortical bone remains a major challenge due to the trade-off between bio- and mechano-compatibility, particularly in naturally derived materials. While composites of calcined bone powder and silane-crosslinked alginate exhibit good biocompatibility and mechanical properties resembling those of trabecular bone, their mechanical properties remain insufficient for cortical bone applications.

This study explores a strategy to address this limitation by optimizing the composite formulation through blending ratio adjustment and nanoparticulation of calcined bone powder. Cylindrical composites (φ 15 mm × h 8 mm) were fabricated by varying the ratios of calcined bone powder (average particle size 246 μm), alginate, and silane cross-linking agent.

Increasing the alginate ratio 10-fold (B/A10-Si) relative to the original formulation (B/A-Si) led to significant increases in elastic modulus, maximum stress, and strain energy which were further improved with the addition of a reduced amount of silane agent (B/A10-Si1/10). Additional enhancement was achieved using nanoparticulated bone powder (average particle size 651 nm), leading to further increases in modulus, strength, and energy by factors of 2.4, 1.7, and 1.4 respectively, compared to B/A10-Si1/10. Overall, the elastic modulus, maximum stress, and strain energy improved 8.4-fold, 18-fold, and 11-fold compared to B/A-Si, approaching values characteristic of cortical bone.

These findings suggest that combining blending optimization with nanoparticulation is a promising strategy to enhance the mechanical performance of naturally derived composites and may expand their applicability to cortical bone replacement.