Formation of a Calcium Phosphate Layer with Immobilized Cobalt Chromite Nanoparticles on Cobalt−Chromium Alloy by a Laser-Assisted Biomimetic Process

Ayako Oyane,Maki Nakamura,Ikuko Sakamaki,Kenji Koga

doi:10.3390/app10165584

Ayako Oyane, Maki Nakamura + Show 2 more

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https://doi.org/10.3390/app10165584

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Abstract

The biocompatibility and osteoconductivity of metallic biomaterials can be achieved by calcium phosphate (CaP) coating. We recently developed a laser-assisted biomimetic (LAB) process for rapid and area-specific CaP coating on several materials. In the present study, the LAB process was applied to cobalt–chromium (Co−Cr) alloy, a metallic biomaterial widely used in orthopedic and dental applications. The LAB process was conducted by irradiation of unfocused pulsed laser light onto the substrate immersed in supersaturated CaP solution. The LAB-processed substrate formed CaP on the irradiated surface within only 5 min and was coated with a micron-thick CaP layer within 30 min by the effects of laser-induced surface modification and heating. Ultrastructural analysis with transmission electron microscopy revealed that the resultant CaP layer was integrated with the underlying substrate through two intermediate layers, an upper chromium oxide layer and a lower Co-rich (Cr-deficient) alloy layer. The CaP layer was loaded with a large number of cobalt chromite (CoCr2O4) nanoparticles. The results obtained offer new insights into the mechanism of CaP coating in the LAB process and future applications of LAB-processed Co−Cr alloys.

Highlights

Calcium phosphate (CaP) is the major inorganic constituent of vertebrate hard tissues, i.e., bones and teeth
The laser-assisted biomimetic (LAB) process was effective for the facile CaP coating of the Co−Cr alloy substrate
Scanning electron microscopy (SEM) observation revealed that the laser-irradiated surface of the substrate was roughened at the microscale within 5 min (Figure 2a)

Summary

Introduction

Calcium phosphate (CaP) is the major inorganic constituent of vertebrate hard tissues, i.e., bones and teeth. Some CaP compounds have been used as biomaterials for hard tissue restoration and replacement These CaP compounds cannot be used alone under high load-bearing conditions due to their insufficient fracture toughness. CaP layer on tough and strong metallic materials is an effective approach to produce osteoconductive biomaterials that can be used under high load-bearing conditions. Bulk Co−Cr alloys exhibit excellent mechanical properties [3], such as high mechanical strength, fracture toughness and strong resistance to fatigue and wear. They are chemically stable (corrosion resistant) and well tolerated in the body due to the passive oxide layer on their surfaces. Co−Cr alloys are categorized as bioinert materials; their osteoconductivity is

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