Development of calcium phosphate/poly(ethylene glycol) composite for injectable bone cement application

Abstract

The rising attention in micro-invasive bone grafting method in orthopaedics demanded for injectable bone filling materials. The injectable bone cement materials should have optimum setting time to provide sufficient time for implantation and prevent delay of operation, good injectability, mechanical strength similar to that of natural bone, and excellent biological response. However, the limitations of calcium phosphate cement (CPC) due to its low mechanical strength, poor injectability and weak cohesion. The objectives of this study are to develop calcium phosphate/poly(ethylene glycol) (CPC/PEG) composite bone cement and investigate the physical, mechanical and biological properties of the cement. In this method, hydroxyapatite (HA) powder was synthesized by using calcium hydroxide, Ca(OH)2, and diammonium hydrogen phosphate, (NH4)2HPO4. The mixture of calcium and phosphorus solution refluxed at 90?. The production of CPC has been done by mixing the wet chemical precipitation derived HA powder with distilled water at certain powder-to-liquid (P/L) ratio, varied at 1.0, 1.3, 1.5 and 1.7. Bioactive ceramic matrix composite was produced by mixing the synthesized powder with liquid phase containing PEG at different PEG amount, varied at 1, 2, 3, 4 and 5 wt%. The powder characterizations involved X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD and FTIR confirmed the formation of pure HA. Morphology analyses of FESEM and TEM illustrated the formation of agglomerated nanorod shape HA particles with size of 150-300 nm length and 10-30 nm width. Afterwards, the produced CPC was investigated for injectability, setting time, compression strength, porosity, anti-washout and cell proliferation capacity. The results of this study revealed that higher P/L ratio contributed to better setting time and compressive strength of CPC but worsen its injectability. The optimum condition achieved by CPC with the P/L ratio of 1.3, which shows 82.5% paste injectability, 88 min initial setting time, 228 min final setting time and 1.344 MPa compressive strength. The study on the effect of PEG on CPC properties has shown significant improvement in setting time, injectability and mechanical strength. The incorporation of 2% PEG into CPC with the P/L ratio 1.3 shows an optimum condition with 85.9% paste injectability, 60 min initial setting time, 209 min final setting time and 1.781 MPa compressive strength. All CPC compositions demonstrated an excellent performance since no cement dissolution or broken throughout 28 days soaking in Ringer's solution, except for the CPC/PEG with the P/L ratio of 1.0 with 3, 4, and 5 wt% PEG additions. The cell culture on CPC microcarriers has proven that the fabricated CPC shows no toxic reaction and cells grow well. This present study shows that the fabricated bioactive ceramic matrix composite is suitable for injectable bone cement applications.