Abstract
Poly(methyl methacrylate) (PMMA) is the most frequently used bone void filler in orthopedic surgery. However, the interface between the PMMA-based cement and adjacent bone tissue is typically weak as PMMA bone cement is inherently bioinert and not ideal for bone ingrowth. The present study aims to improve the affinity between the polymer and ceramic interphases. By surface modifying nano-sized hydroxyapatite (nHAP) with ethylene glycol and poly(ɛ-caprolactone) (PCL) sequentially via a two-step ring opening reaction, affinity was improved between the polymer and ceramic interphases of PCL-grafted ethylene glycol-HAP (gHAP) in PMMA. Due to better affinity, the compressive strength of gHAP/PMMA was significantly enhanced compared with nHAP/PMMA. Furthermore, PMMA with 20 wt.% gHAP promoted pre-osteoblast cell proliferation in vitro and showed the best osteogenic activity between the composites tested in vivo. Taken together, gHAP/PMMA not only improves the interfacial adhesion between the nanoparticles and cement, but also increases the biological activity and affinity between the osteoblast cells and PMMA composite cement. These results show that gHAP and its use in polymer/bioceramic composite has great potential to improve the functionality of PMMA cement.
Highlights
Poly(methyl methacrylate) (PMMA) is well known as bone cement due to its wide utilization in orthopedic surgery in procedures such as osteoporotic vertebral fractures, treatment of bony metastases and fixation of components in arthroplasties [1 –4]
The thermogravimetric analyzer (TGA) result of particles without or with polymer modification demonstrates that the grafting ratio was estimated to be approximately 14 wt.% for EG-modified nHAP (E-HAP) and approximately 22 wt.% for gHAP
transmission electron spectrometer (TEM) micrographs of particles without or with PCL modification shows that the particles before and after the grafting procedures both maintained a spherical morphology, and a corona was clearly seen around gHAP, which is an indication of successful grafting of polymers to nano-sized hydroxyapatite (nHAP) particles
Summary
Poly(methyl methacrylate) (PMMA) is well known as bone cement due to its wide utilization in orthopedic surgery in procedures such as osteoporotic vertebral fractures, treatment of bony metastases and fixation of components in arthroplasties [1 –4]. PMMA bone cement provides immediate pain relief, and mechanical stability [5]. PMMA is an acrylic polymer and is formed by the mixture of a liquid MMA monomer and a powder MMA polymer. It has been the only material used for anchoring artificial replacements to contiguous bones [6]. The physical and chemical properties of PMMA are far from ideal from a spine surgeon’s point of view. Poor biological activity of PMMA leads to poor interaction between the local bone and PMMA cement [4,6]
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