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Lack of bioactivity and monomer toxicity are limiting factors of polymethyl methacrylate (PMMA) bone cement in orthopedic applications. Herein, we address these shortcomings by proposing two-dimensional magnesium phosphate (MgP) nanosheets and hydroxyapatite (HA) nanofibers as novel fillers in PMMA bone cement nanocomposites. Two-dimensional MgP nanosheets and one-dimensional HA nanofibers were synthesized by tuning the crystallization of the sodium-magnesium-phosphate ternary system and hydrothermal homogeneous precipitation, respectively. We show that MgP nanosheets exhibit antibacterial properties against Escherichia coli (E. coli). In addition, HA nanofibers with high level of bioactivity are the proper choice to induce cell viability in the nanocomposite. Results indicate that the combination of both fillers can act as deformation locks enhancing the compressive strength of the nanocomposites. The synthesized nanocomposite possesses excellent bioactivity, mechanical properties, and cytocompatibility potentially opening new paradigm in the design of next generation bone cement composites., Competing Interests: Declaration of competing interest The authors declare no conflict of interests., (Copyright © 2019 Elsevier B.V. All rights reserved.)

An oleic acid-assisted solvothermal method has been utilized to prepare hydroxyapatite (HA) nanofibers with a high flexibility and aspect ratio. Understanding the role of oleic acid in the synthesis of HA may provide effective routes for the design of advanced biomaterials. The concentration of OH− ions ([OH−]) has a great impact on the reaction system, which in turn affects the nucleation and crystal growth of HA. In this work, the effect of oleic acid on the morphology and structure of the as-prepared products under different concentrations of NaOH was investigated by XRD, FTIR and FE-SEM. The formation process of HA was also explored to better explain the role of oleic acid based on structured characteristics and morphology evolution. These results showed that oleic acid molecules absorbed on the surface of HA would effectively induce a one-dimensional crystal growth, even if the crystal growth habit had been changed under different [OH−]. For [OH−] < 1.50 M, [OH−]-responsive oleic acid and its corresponding behavior as a pH buffer can regulate pH at a relatively constant value. Besides, the flexible ultralong HA nanofibers can be formed at [OH−] = 1.25–1.50 M, while the crystallite size and preferred growth along the c-axis were both improved with an increase in [OH−] added. [ABSTRACT FROM AUTHOR]

Commercial poly methyl methacrylate (PMMA)-based cement is currently used in the field of orthopedics. However, it suffers from lack of bioactivity, mechanical weakness, and monomer toxicity. In this study, a PMMA-based cement nanocomposite reinforced with hydroxyapatite (HA) nanofibers and two-dimensional (2D) magnesium phosphate MgP nanosheets was synthesized and optimized in terms of mechanical property and cytocompatibility. The HA nanofibers and the MgP nanosheets were synthesized using a hydrothermal homogeneous precipitation method and tuning the crystallization of the sodium-magnesium-phosphate ternary system, respectively. Compressive strength and MTT assay tests were conducted to evaluate the mechanical property and the cytocompatibility of the PMMA-HA-MgP nanocomposites prepared at different ratios of HA and MgP. To optimize the developed nanocomposites, the standard response surface methodology (RSM) design known as the central composite design (CCD) was employed. Two regression models generated by CCD were analyzed and compared with the experimental results, and good agreement was observed. Statistical analysis revealed the significance of both factors, namely, the HA nanofibers and the MgP nanosheets, in improving the compressive strength and cell viability of the PMMA-MgP-HA nanocomposite. Finally, it was demonstrated that the HA nanofibers of 7.5% wt and the MgP nanosheets of 6.12% wt result in the PMMA-HA-MgP nanocomposite with the optimum compressive strength and cell viability. [ABSTRACT FROM AUTHOR]