Search

Studies have demonstrated that polymeric biomaterials have the potential to support osteoblast growth and development for bone tissue repair. Poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PHBV), a bioabsorbable, biocompatible polyhydroxy acid polymer, is an excellent candidate that, as yet, has not been extensively investigated for this purpose. As such, we examined the attachment characteristics, self-renewal capacity, and osteogenic potential of osteoblast-like cells (MC3T3-E1 S14) when cultured on PHBV films compared with tissue culture polystyrene (TCP). Cells were assayed over 2 weeks and examined for changes in morphology, attachment, number and proliferation status, alkaline phosphatase (ALP) activity, calcium accumulation, nodule formation, and the expression of osteogenic genes. We found that these spindle-shaped MC3T3-E1 S14 cells made cell–cell and cell–substrate contact. Time-dependent cell attachment was shown to be accelerated on PHBV compared with collagen and laminin, but delayed compared with TCP and fibronectin. Cell number and the expression of ALP, osteopontin, and pro-collagen α1(I) mRNA were comparable for cells grown on PHBV and TCP, with all these markers increasing over time. This demonstrates the ability of PHBV to support osteoblast cell function. However, a lag was observed for cells on PHBV in comparison with those on TCP for proliferation, ALP activity, and cbfa-1 mRNA expression. In addition, we observed a reduction in total calcium accumulation, nodule formation, and osteocalcin mRNA expression. It is possible that this cellular response is a consequence of the contrasting surface properties of PHBV and TCP. The PHBV substrate used was rougher and more hydrophobic than TCP. Although further substrate analysis is required, we conclude that this polymer is a suitable candidate for the continued development as a biomaterial for bone tissue engineering.

Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has employed transmission electron microscopy (TEM), involving morphological observation, electron diffraction and energy-dispersive X-ray spectrometry (EDX), as an effective analytical technique to evaluate the powders at a microscopic level. The HA and fHA particles were elongated platelets about 20×60 nm in size, while FA particles were over twice this size. Calcination of the HA and fHA powders at 1000 °C for 1 h resulted in increased grain size and crystallinity. The calcined fHA material appeared to possess a crystal structure intermediate between HA and FA, as evidenced by the (3 0 0) peak shift in XRD, as well as by the position of the hydroxyl bands in the FTIR spectra. This result was consistent with electron diffraction of individual particles. Small levels of impurities in some of the powders were identified by EDX and electron diffraction, and the carbonate content was detected by FTIR. The use of TEM in conjunction with the bulk techniques has allowed a more thorough assessment of the apatites, and has enabled the constituents in these closely related apatite powders to be identified.