Osteoblastic cell responses and antibacterial efficacy of Cu/Zn co-substituted hydroxyapatite coatings on pure titanium using electrodeposition method

Abstract

Effective physiological bone integration and absence of bacterial infection are essential for a successful orthopaedic or dental implant. This work elucidated the antibacterial efficacy and cytocompatibility of electroplated Cu(II) and Zn(II) co-substituted hydroxyapatite (HAP) (i.e., ZnCuHAP) coating on commercially pure titanium (Ti-cp). To improve the antibacterial property of pure HAP, Cu 2+ was substituted into its structure.Simultaneously, Zn 2+ is co-substituted as secondary material into CuHAP to offset the potential cytotoxicity of Cu, because elevated Cu concentration is toxic. The as-deposited coatings were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Co-doping of Zn 2+ and Cu 2+ into HAP reduced the porosity, resulting in a denser coating. The Zn 2+ and Cu 2+ ions were homogenously co-deposited into HAP films. Potentiodynamic polarisation test revealed 2 that the ZnCuHAP covered coating provided good barrier characteristics and achieved superior corrosion protection for Ti substrates. The as-prepared ZnCuHAP coating was found to be highly effective against Escherichia coli in vitro. In vitro biocompatibility tests and MTT were employed to assess the cytotoxicity of ZnCuHAP coating with osteoblast-like MC3T3-E1 cells. No adverse effect or cytotoxicity on osteoblasts by Zn/Cu addition was observed, revealing that the co-substitution of Zn in CuHAP efficiently offsets the adverse effects of Cu and improves the performance compared with that of pure HAP. 15 comparison with the HAP coating and the control. Antimicrobial results revealed that Cu ions released from ZnCuHAP present a strong bactericidal effect against these organisms (antimicrobial ratio > 95%). This enhancement may be due to the high release of copper in ZnCuHAP in the PBS medium after 24 h incubation (based on the ICP-AES analysis).The antibacterial tests results revealed that pure HAP coating has no antibacterial property.The pure HAP plate showed more colonies than the control sample (Fig. 6). This finding showed that proteins, amino acids, and other organic matter are readily adsorbed on the HAP surface, which could favour adsorption and replication of bacteria on the coating, usually causing implant-related infections [37]. Therefore, endowing antimicrobial properties to HAP is necessary. Several recent studies have introduced antimicrobial activity of materials that involve Cu(II) ions. Du et al. [38] have suggested that chitosan nanoparticles loaded with Cu(II) ions interact with bacterial cell membranes of E. coli, causing structural changes and, eventually, cell death. Nan et al. [39] also suggested that structure of the outer cell membrane responsible for cell permeability is significantly altered for E. coli after contact with antimicrobial stainless steel with Cu(II) ions. This finding indicates that cell walls were badly undermined, and numerous cellular contents are released. Notably, Zn ions released fromZnCuHAP may also exhi...

Cationic and Anionic Substitutions in Hydroxyapatite

“…The produced systems include the co-substitution of zinc/silver [209], silver/strontium [211], carbonate/strontium [492], carbonate/magnesium [454,493], carbonate/sodium [494], carbonate/silicate [495], yttrium/silicon [496], zinc/silicate [497], zinc/copper [498], strontium/cerium [499], magnesium/ strontium [500], magnesium/silver [501], and carbonate/silicate/magnesium [454]. However, the co-substitution of multiple (more than two) ions has not deeply and systematically attempted and investigated, and thus, it can be considered as a promising research field to be still and further explored and expanded [502,480].…”

Antimicrobial dental implant functionalization strategies —A systematic review

“…However, there are controversies concerning the effects of Zn on osseointegration and biocompatibility. On the one hand, Zn surfaces increase initial adhesion, spreading activity, alkaline phosphatase activity, collagen secretion and extracellular matrix mineralization of eukaryotic cells 6,108,129,164) . On the other hand, they exhibit dosedependent negative effects on cell proliferation, cell morphology, osteogenic gene expression and cell viability of eukaryotic cells 135) .…”

Corrosion resistance and cytocompatibility studies of zinc-doped fluorohydroxyapatite nanocomposite coatings on titanium implant

“…Zn incorporation into implants was shown to stimulate bone formation around the implant and reduce inflammatory response [17]. Recent studies have shown that Zn-doped HA coating can release trace Zn 2+ in the degradation process, which is favourable to improve cell proliferation [11,17,18].…”

“…Improvement of biological and physicochemical properties of HA can be achieved by doping with ions that are usually present in natural apatites of vertebrate skeletal systems [8]. A wide variety of anions, cations and functional groups, such as Na + [9], Sr 2+ [10], Zn 2+ [11], Mn 2+ [12], SiO 4 4− [13], F − [14], Cl − [15], and CO 3 2− [16], can be introduced into the single phase HA lattice. Amongst these substitutions, zinc and fluorine are widely considered as potential substituents because of their biological relevance [17].…”