Judith A. Juhasz

Nano-sized hydroxyapatite (nHA) and carbonate-substituted hydroxyapatite (nCHA) particles were incorporated into a poly-2-hydroxyethylmethacrylate/polycaprolactone (PHEMA/PCL) hydrogel at a filler content of 10 wt%. Fourier transform infrared absorption, transmission electron microscopy, x-ray diffraction and scanning electron microscopy were used to analyse the physical and chemical characteristics of the calcium phosphate fillers and resultant composites. Nano-sized calcium phosphate particles were produced with a needle-like morphology, average length of 50 nm and an aspect ratio of 3. The nanoparticles were uniformly distributed in the polymer matrix. The addition of both HA and CHA in nano-form enhanced the bioactivity and biocompatibility of the PHEMA/PCL matrix. The carbonate-substitution has allowed for improved bioactivity and biocompatibility of the resultant composite, indicating the potential of this material for use in bone tissue engineering.

The surface transformation reactions of bioactive ceramics were studied in vitro in standard K9-SBF solution and in human blood serum (HBS)—containing simulated body fluid (SBF). The calcium phosphate ceramics used for this study were stoichiometric hydroxyapatite (HA), β-tricalcium phosphate (β-TCP) and brushite. Immersion of each calcium phosphate tested in this study, in simulated body fluid, led to immediate surface precipitation of apatite. The use of HBS resulted in a delay in the onset of precipitation and a significant inhibition of the dissolution reaction normally observed for brushite in solution. However, apatite formation still occurred. The use of HBS and SBF in this investigation, which has shown the ability to induce similar crystal growth as that observed in vivo, suggests that there is scope for the use of serum proteins in simulated body fluid in order to create a protein-rich surface coating on biomedical substrates.

Bioactive glass‐ceramic apatite‐wollastonite (A‐W) has been incorporated into polyethylene in particulate form to create new bioactive composites for potential maxillofacial applications. The effects of varying the volume fraction of glass‐ceramic A‐W filler and the glass‐ceramic A‐W particle size were investigated by measuring the bonding strength of the bonelike apatite layer formed on the surface of glass‐ceramic A‐W–polyethylene composites. The bonding strength was evaluated via a modified ASTM C‐333 standard in which a tensile stress was applied to the substrate and the strength of the bioactive layer was compared with that formed on commercially available hydroxyapatite–polyethylene composite samples, HAPEX™. The composites demonstrated greater bonding strength with increased filler content and reduced filler particle size (maximum 6.9 ± 0.5 MPa) and a marginally greater bonding strength as compared with HAPEX™ (2.8 ± 0.5 MPa), when glass‐ceramic A‐W–polyethylene composite samples with the same filler content were tested. The higher bonding strength of the apatite layer formed on the A‐W–polyethylene composite samples suggests that, in addition to maxillofacial applications, these composites might also be utilized in applications involving higher levels of load bearing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 952–959, 2003

The bioactivity of a range of glass-ceramic apatite–wollastonite (A–W) – polyethylene composites (AWPEXs) with glass-ceramic A–W volume percentages ranging from 10 to 50, has been investigated in an...