RESEARCH ARTICLE Effect of rare earth oxide microparticles on mechanical, corrosion, antibacterial, and hemolytic behavior of Mg-Hydroxyapatite composite for orthopedic applications – A preliminary in-vitro study Divyanshu Aggarwal 1 | Vinod Kumar 1 | Siddharth Sharma 2 1 Department of Mechanical Engineering, Thapar Institute of Engineering and Technology, Patiala, India 2 Department of Biotechnology Engineering, Thapar Institute of Engineering and Technology, Patiala, India Correspondence Divyanshu Aggarwal, Department of Mechanical Engineering, Thapar Institute of Engineering and Technology, Patiala, Punjab 147004, India. Email: divyanshuaggarwal95@gmail.com Abstract The current study focused on developing a multifunctional Mg-based biodegradable composite that mitigates the trade-off between strength, antibacterial, and cytotoxic- ity behavior for orthopedic bone implants. The composite has been reinforced with natural mineral-based Hydroxyapatite and rare earth oxide (REO): Neodymium oxide. The effect of different concentrations of REO on the mechanical, antibacterial, and corrosion properties was analyzed. The antibacterial properties were assessed against gram-positive B. Subtilis and gram-negative E. Coli bacterial pathogens. Moreover, the cytotoxicity of the composites was assessed via Hemolysis percentage calculations. In addition, the microstructure characterization was performed via FESEM, XRD, and EDS techniques, and different intermetallic phase formations were recorded. Contact angle measurements were done via the sessile drop method to analyze the impact of rare earth oxide on the surface properties of the synthesized composites and their relationship with bacterial adhesion. The corrosion studies and swelling rates were performed under PBS and DMEM solutions. The composite with the addition of 1.5% REO outperformed the experiments with a compressive strength of 126.4 MPa, and a corrosion rate less than 0.2 mm/yr. The corrosion rates and degree of swelling were seen to be more stable in DMEM solution as compared to PBS. Improved anti- bacterial rates were observed against both pathogens after the addition of REO along with a hemolysis percentage less than 5% for Mg-HA-1.5Nd 2 O 3 . The composites showed increased hydrophobicity (>75%) by the addition of 1.5% REO. Hence, it was concluded that REO (Nd 2 O 3 ) addition to the Mg-Hydroxyapatite composite is a feasi- ble choice as a biomaterial for bone implant applications. KEYWORDS antibacterial, compressive strength, corrosion, hemolysis, Mg-Hydroxyapatite composite, neodymium oxide 1 | INTRODUCTION In the last decade, the demand for multifunctional biomaterials has grown exquisitely, which can provide a balance between mechanical Abbreviations: AB, Antibacterial; B. Subtilis, Bacillus Subtilis; CFU, Colony forming units; DMEM, Dulbecco's Modified Eagle Medium; E. Coli, Escherichia Coli; EDTA, Ethylenediamine tetraacetic acid; HA/HAP, Hydroxyapatite; HR, Hemolysis Rate; IZD, Inhibition zone diameter; MBC, Minimum bactericidal concentration; Mg, Magnesium; MIC, Minimum inhibitor concentration; NA, Nutrient Agar; NdO/Nd 2 O 3 , Neodymium Oxide; OD, Optical Density; PBS, Phosphate Buffer Saline; REO, Rare earth oxide; S. Aureus, Staphylococcus Aureus; UCS, Ultimate compressive strength. Received: 26 August 2022 Revised: 14 January 2023 Accepted: 30 January 2023 DOI: 10.1002/jbm.b.35228 J Biomed Mater Res. 2023;1–15. wileyonlinelibrary.com/journal/jbmb © 2023 Wiley Periodicals LLC. 1