Induction suspension plasma sprayed biological-like hydroxyapatite coatings

Abstract

Substituted hydroxyapatite coatings with different ions (Mg, Na, K, Cl, F) have been developed by the induction suspension plasma spray process. Suspensions were prepared with sol-gel. The main objective of this study was to demonstrate that induction suspension plasma spray technology possesses high material composition flexibility that allows as-sprayed coatings to closely mimic natural bone composition. Long-term in vitro behaviour of as-sprayed substituted coatings was evaluated with simulated body fluid. Data on the suspensions showed the formation of a pure hydroxyapatite phase. Transmission electron microscopy characterized various preparation stages of the suspensions. As-sprayed samples were distinguished by X-ray diffraction and scanning electron microscopy. Substituted elements were quantified by neutron activation. A well-crystallized hydroxyapatite phase was produced with concentration in various substitutions very close to natural bone composition. Ca/P and (Ca + Mg + Na + K)/P ratios provided evidence of the introduction of different cations into apatite structures. The immersion of samples into simulated body fluid led to the nucleation and growth of a flake-like octacalcium phosphate crystal layer at the surface of as-sprayed coatings after one week. Proof of octacalcium phosphate transformation and its partial dissolution and direct re-precipitation into apatite was disclosed by local energy dispersive spectroscopy and microstructure observation. Formation of a Ca/P ratio gradient from the precipitated layer surface to the as-sprayed coatings interface was observed after four weeks once the octacalcium phosphate crystals reached a critical size, resulting in the formation of a rich apatite layer at the interface after six weeks. A set of mechanisms has been proposed to explain these findings.

In Vitro and in Vivo Analysis of Mineralized Collagen-Based Sponges Prepared by a Plasma- and Precursor-Assisted Biomimetic Process

“…Apatite coatings with higher solubility can be produced by a biomimetic process in which apatite is formed in a supersaturated calcium phosphate (CaP) solution that is similar to body fluid. Due to its mild coating conditions, a biomimetic process is suitable for thermally unstable organic polymers, which is an advantage over practical coating techniques such as plasma spraying, , pulsed laser deposition, , and sputtering. , To date, the process of biomimetic apatite coating has been applied to various collagen-based materials. − However, these materials were in the form of 2D sheets, films, or composites in most cases, and there has been little attempt to coat both the outer and inner surfaces of collagen-based 3D porous sponges with apatite.…”

Bioactive surface modifications through thermally sprayed hydroxyapatite composite coatings: a review of selective reinforcements

“…Reinforcing with Cu, Ag, and Zn provides antibacterial and anti-inflammatory properties to HA-coated implants. 250 There have been several reports on the addition of silver, 42,138,141,149,152,156,190,195,341-347 strontium, 97,149,151,165,168,196,281,[348][349][350] magnesium, 189,196,274,281,351,352 and other materials 27,79 to HA. A summary of these studies showing the relevance of these reinforcements to enhance coating properties is given in Table 9.…”

Periodontal tissue engineering using an apatite/collagen scaffold obtained by a plasma‐ and precursor‐assisted biomimetic process

“…24 The low-crystalline apatite coating process using supersaturated CaP solutions (biomimetic process) is a mild liquid-phase method; hence, this process can be carried out at normal temperature and pressure, and can be used with low-melting-point substrates including organic polymers. These are notable advantages to the biomimetic process compared to commonly used CaP coating processes such as plasma spraying, 25,26 pulse laser deposition, 27,28 and sputtering methods. 29,30 Oyane et al 31 previously developed a relatively simple biomimetic technique, the plasma-and precursorassisted biomimetic process.…”