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Keywords:

Calcium phosphate Electrodeposition

Abstract:

Introduction: Functionalisation of titanium (Ti) implants with calcium phosphate (CaP) is a widely used approach in orthopaedic applications to obtain a mechanically strong system that is Osteoconductive . In order to deposit CaP in a controlled way on complex 3D Ti surfaces, like scaffolds, this study applied a perfusion electrodeposition (P-ELD) system. Materials and Methods: 3D Ti-scaffolds were fabricated by selective laser melting. A P-ELD system was developed to deposit CaP onto Ti-scaffolds (cathode) using a platinum ring as anode. A supersaturated calcium phosphate (SCP) solution was used as electrolyte. A full factorial (24) design was performed to analyse the effect of current density (I), temperature (T), deposition time (t) and flow rate (f) on the characteristics of the deposited CaP. The parameter I and t were optimised by performing P-ELD at: (a) varying I at constant t (12 hr) and (ii) varying t at constant I (3 mA/cm2). The coating morphology, distribution, thickness, crystalinity and Ca/P ratio were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe micro- analysis (EPMA). The biocompatibility of CaP-coated Ti-scaffolds was tested by live-dead staining and SEM-analysis of human periosteum derived cells (HPDCs) seeded scaffolds after 7 days of culture. Results and Discussion: CaP deposition increased with increasing t, T and f, whereas 20 & 40 mA/cm2 of I were too high and disrupted CaP deposition. In fact, the effect of t and the t-f interaction on the CaP deposition were statistically significant (p=0.001 & p=0.019). 50 oC and 10 ml/min were selected for subsequent experiments. SEM analysis showed that P-ELD for t > 6 hr with 2 – 10 mA/cm2 resulted in a full coating of the scaffolds, up to a thickness of 40μm and with a Ca/P ratio of 1.41. Interestingly, P-ELD at 5 mA/cm2 for 6 hr produced a cauli flower-like crystal structure of 28 μm thick with a Ca/P ratio of 1.45. XRD analysis indicated that the CaP coatings were carbonated synthetic hydroxyapatite. Live-dead staining of HPDCs cultured on coated Ti-scaffolds for 7 days showed high cell viability and biocompatibility. SEM imaging showed that the HPDCs had a fibroblastic phenotype and interacted with the CaP coating. Conclusion: Perfusion electrodeposition (P-ELD) can become a useful tool to functionalise complex Ti structures (e.g. scaffolds) with CaP, in which the physiochemical properties of the CaP coating could be controlled and optimised for effective bone formation.