Hydroxyapatite-poly(d,l-lactide) Nanografts. Synthesis and Characterization as Bone Cement Additives

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Hydroxyapatite (HA) is a key component of bone, making it a desirable material for bone regeneration and repair.
• Polyesters are biocompatible and biodegradable polymers widely used in biomedical applications.
• Combining HA with polyesters can lead to advanced composite materials with enhanced properties.

Purpose of the Study:

• To synthesize novel hydroxyapatite/polyester nanografts using a "graft-from" polymerization technique.
• To characterize the synthesized nanografts and evaluate their molecular properties.
• To assess the potential of these nanografts as additives for improving commercial bone cement.

Main Methods:

• "Graft-from" polymerization of d,l-lactide initiated by hydroxyapatite nanocrystals ([Ca5(OH)(PO4)3]2) and catalyzed by tin(II)-2-ethylhexanoate.
• Model polymerizations using cyclooctanol as an initiator to confirm surface grafting.
• Characterization using size-exclusion chromatography, NMR, FT-IR spectroscopy, thermal analysis, and mechanical testing.

Main Results:

• Successful synthesis of hydroxyapatite/polyester nanografts with controlled molecular masses (Mn between 4250 Da and 6100 Da).
• Monimodal molecular mass distributions were observed for the synthesized polymers.
• Addition of nanografts to commercial bone cement (Simplex P Speedset) demonstrably improved its thermal and mechanical properties.

Conclusions:

• Hydroxyapatite/polyester nanografts can be effectively synthesized via "graft-from" polymerization.
• These nanografts serve as effective additives for enhancing the performance of bone cement.
• The improved thermal and mechanical properties suggest potential for these nanografts in orthopedic applications.