Antibiotic-Releasing Porous Shell Cements

Background/Objectives: Solid bone cement is a poor vehicle for delivering antibiotics, and porous bone cement lacks mechanical robustness. Inspired by the different structural phases of bone, we hypothesized that porous shell cements (PSCs) could be synthesized to be both mechanically resilient and effective in eluting antibiotics. Our objective was to synthesize and characterize PSCs and compare their physicochemical properties to solid and porous cements. Methods: PSCs were synthesized with thin versus thick outer porous shells and compared to homogenous solid and porous cements as controls. Porosity and architecture were assessed through scanning electron microscopy and microcomputed tomography. Mechanical properties were quantified by compression testing. Antibiotic release kinetics and antibiotic activity were measured via release assays, disc diffusion assays, and minimum inhibitory concentration tests. Results: PSCs exhibit both solid and porous regions within a single bone cement construct with enhanced surface area to volume ratios in porous regions. Cements with porous regions have lower synthesis heat during polymerization. The mechanical strength of PSCs correlates with the ratio of solid core to porous shell thickness. The addition of the porous shell layer significantly increases antibiotic elution and increases the inhibition of Staphylococcus aureus and Staphylococcus epidermidis strains. Conclusions: We are able to synthesize customizable PSCs that balance the mechanical strength of solid bone cement with the antibiotic release profile of porous cement as a new biomaterial strategy to prevent orthopaedic device infection.