Research Article

Optimizing Diopside for Bone Repair: Structural, Mechanical, and Biological Effects of Ce/Co Co-Substitution

Hsiu-Wen Yang 1, Yun-Han Su 1, Yu-Sheng Tseng 1, Dorian Amir Henry Hanaor 2, Wen-Fan Chen 1 *
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1 Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan2 Faculty of Science and Engineering, Southern Cross University, East Lismore, NSW, 2480, Australia* Corresponding Author
International Journal of Clinical Medicine and Bioengineering, 6(1), 2026, 1-13, https://doi.org/10.35745/ijcmb2026v06.01.0001
Submitted: 27 November 2025, Published: 30 March 2026
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ABSTRACT

We examined the influence of simultaneous cerium (Ce) and cobalt (Co) substitution in diopside (CaMgSi2O6) on its structural, mechanical, and biological behavior. Moderate incorporation levels (0.25–0.50 mol of Ce/0.25–0.50 mol of Co) produced the most balanced performance. At the Ce 0.50 mol/Co 0.50 mol composition, the material achieved the highest hardness (174.8 Hv), a remarkable enhancement compared with pure diopside (14.9 Hv), which is attributed to improved microstructural densification. In contrast, high co-substitution levels (≥ 0.75/0.75 mol) caused lattice distortion, increased porosity, and reduced mechanical stability. Bioactivity tests showed that the Ce 0.25 mol/Co 0.25 mol composition presented hydroxyapatite formation in simulated body fluid, while excessive co-substitution suppressed Ca, Si, and P participation and limited hydroapatite nucleation.  Cell assays revealed a clear decrease in viability with increasing Co content, indicating that Co release is the primary factor affecting cytocompatibility and mineralization ability. Through low-to-moderate Ce/Co substitution, mechanical strength enhances while maintaining acceptable mineralization capability, whereas high substitution compromises performance. The Ce 0.25–0.50 mol/Co 0.25–0.50 mol compositions exhibited optimal performance, while further reduction of Co content effectively lowered cytotoxicity.
Keywords: CaMgSi2O6, Cerium, Cobalt, Co-substitution, Bioceramic

CITATION (APA)

Yang, H.-W., Su, Y.-H., Tseng, Y.-S., Hanaor, D. A. H., & Chen, W.-F. (2026). Optimizing Diopside for Bone Repair: Structural, Mechanical, and Biological Effects of Ce/Co Co-Substitution. International Journal of Clinical Medicine and Bioengineering, 6(1), 1-13. https://doi.org/10.35745/ijcmb2026v06.01.0001

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