Bioactive, Ion-Releasing PMMA Bone Cement Filled with Functional Graphenic Materials

Area of Science:

• Biomaterials Engineering
• Nanotechnology
• Orthopedic Materials Science

Background:

• Graphene oxide and functionalized graphenic materials (FGMs) show potential for creating bioactive poly(methyl methacrylate) (PMMA)-based bone cements.
• Previous attempts were limited by low filler loadings due to aggregation and interference with the curing process, hindering bioactive effects.
• Higher loadings of graphenic fillers typically compromise cement strength.

Purpose of the Study:

• To overcome limitations of graphenic fillers in PMMA bone cements by developing a custom formulation with significantly higher FGM content.
• To enhance both the mechanical properties and programmable bioactivity of PMMA-based bone cements.
• To establish design criteria for future FGMs enabling dynamic biological activity in bone cements.

Main Methods:

• Developed a custom PMMA cement formulation incorporating bioactive FGMs at significantly higher concentrations than previously reported.
• Characterized the mechanical properties (compressive strength, flexural strength, flexural stiffness) of the developed cements.
• Assessed the controlled release of osteogenic calcium ions and the in vitro biological response (alkaline phosphatase expression) of human mesenchymal stem cells.

Main Results:

• Achieved an order of magnitude higher graphenic filler loading compared to prior studies.
• Cements with 1 wt% FGM met or exceeded ASTM requirements for bone cement, exhibiting compressive strengths of 78-88 MPa and flexural strengths of 74-81 MPa.
• Demonstrated controlled release of 5 ± 2 µmol Ca2+ per gram over 28 days and a 290% increase in alkaline phosphatase expression in human mesenchymal stem cells.

Conclusions:

• The developed custom cement formulation effectively integrates high loadings of FGMs, enhancing both mechanical integrity and bioactivity.
• These FGMs offer a promising platform for creating next-generation bone cements with programmable and dynamic biological functions.
• The study provides crucial design criteria for future advancements in bioactive bone cement technology using FGMs.