In vitro biological response of plasma electrolytically oxidized and plasma‐sprayed hydroxyapatite coatings on Ti–6Al–4V alloy

Abstract

Plasma electrolytic oxidation (PEO) is a relatively new surface modification process that may be used as an alternative to plasma spraying methods to confer bioactivity to Ti alloy implants. The aim of this study was to compare physical, chemical and biological surface characteristics of two coatings applied by PEO processes, containing different calcium phosphate (CaP) and titanium dioxide phases, with a plasma-sprayed hydroxyapatite (HA) coating. Coating characteristics were examined by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, surface profilometry, and wettability tests. The biological properties were determined using the human osteoblastic cell line MG-63 to assess cell viability, calcium and collagen synthesis. The tests showed that PEO coatings are significantly more hydrophilic (6%) and have 78% lower surface roughness (Ra) than the plasma-sprayed coatings. Cell behavior was demonstrated to be strongly dependent on the phase composition and surface distribution of elements in the PEO coating. MG-63 viability for the TiO2 -based PEO coating containing amorphous CaPs was significantly lower than that for the PEO coating containing crystalline HA and the plasma-sprayed coating. However, collagen synthesis on both the CaP and the TiO2 PEO coatings was significantly higher (92% and 71%, respectively) than on the plasma-sprayed coating after 14 days. PEO has been demonstrated to be a promising method for coating of orthopedic implant surfaces.

Hydroxyapatite coating deposited on grade 4 Titanium by Plasma Electrolytic Oxidation

“…Similar results were reported by Yeung et al 36 , who assessed the cytocompatibility of PEO coated TiO 2 with human osteosarcoma cells (MG-63s) and found that PEO coated samples had fewer viable cells in comparison with plasma-sprayed HA samples and TCPS. The same authors believe that cellular behavior may be inhibited by the specific morphology or chemical composition of the PEO coating 36 .…”

“…The same authors believe that cellular behavior may be inhibited by the specific morphology or chemical composition of the PEO coating 36 . For 5 days of cultivation, the sample treated for 600 s was the only that presented cellular growth significantly less than the untreated sample, which was used as a control to compare with the treated samples (p <0.01).…”

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…In addition, the MAO process could be performed in aqueous electrolytes, containing dissolved Ca-and PO 4 -containing compounds only [542][543][544][545][546][547][548][549][550][551][552][553]. In this case, CaPO 4 was deposited in the single stage.…”

Morphology and antimicrobial properties of hydroxyapatite–titanium oxide layers on the surface of Ti–6Al–4V alloy

“…However, the role of calcium phosphates and, particularly, of hydroxyapatite is considered especially important [7][8][9][10][11][12][13][14]. One of the preliminary indications of hydroxyapatite presence in the surface layer is the Ca:P ratio in atomic percent.…”

“…HA is a naturally occurring apatite and a major mineral component of bones and teeth. The biocompatibility of HA has been thoroughly investigated, and it has been well established that when HA is applied on or included into titanium dioxide surface, it spontaneously bonds with a living bone [7][8][9][10][11][12][13][14].…”