Coatings for osseointegration of metallic biomaterials

doi:10.1016/B978-1-78242-303-4.00011-9

Surface Coating and Modification of Metallic Biomaterials

2015, Pages 345-358

https://doi.org/10.1016/B978-1-78242-303-4.00011-9 Get rights and content

Abstract

This chapter discusses the application of coatings for improving the osseointegration of metallic implant materials. First, the definition of osseointegration and the methods for evaluating the osseointegration are described. The chapter then reviews the biological process of osseointegration. Second, the definition, preparation methods, and mechanisms to promote osseointegration of the coatings are discussed. At the end, the current clinical application and the future trends of these coatings are reviewed.

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Cited by (7)

Surface characterization of titanium-based substrates for orthopaedic applications
2021, Materials Characterization
Citation Excerpt :
Following the implantation of the biomaterial, its surface becomes in contact with the surrounding fluid, and that interaction affects the adsorption of molecules and proteins which mediate cell adhesion. In this sense, micro-scale roughness enhance the surface area available for cell adhesion, in particular MSC, which may undergo osteoblast differentiation in order to form bone matrix and, ultimately, a successful osseointegration and therefore, improved clinical outcomes [69]. In addition, osteoblasts appear to act as paracrine regulators of the osteogenic commitment in MSC populations present nearby the implant site.
Orthopaedic implants for load-bearing applications are usually composed of titanium-based materials. Aiming to propose a strategy able to improve the bone-implant interface on these implants, commercially pure titanium and Ti6Al4V alloy were subjected to anodic oxidation, hydrothermal treatment and to anodic oxidation followed by hydrothermal treatment and the produced oxide film was investigated. In addition, different mechanical (as-received vs mechanical polished) and chemical pre-treatments (alcohol cleaning vs acidic pre-treatment) were studied. No significant differences were found between the chemical pre-treatments, whereas upon different surface treatments the TiO₂ layer presented different characteristics, namely regarding its crystallinity, roughness, thickness and wettability. The hydrothermal treatment followed by immersion for 24 h in 5XPBS was effective in creating a potentially bioactive oxide film, given the presence of anatase and rutile phases, and a hydrophilic layer for both Ti materials. Ti grade 2 subjected to alcohol cleaning and hydrothermal treatment resulted in a surface roughness of 226.7 ± 3.1 nm and water contact angle of 67.2 ± 8.7°, whereas for the Ti grade 5 subjected to the same surface treatment, Ra was equal to 20.4 ± 1.7 nm and the water contact angle to 83.5 ± 4.7°. In this context, the hydrothermal treatment is proposed as a simple treatment capable of improving the characteristics of the implant surface, thereby promoting osteoconductivity.
Effects of solution composition and electrophoretic deposition voltage on various properties of nanohydroxyapatite coatings on the Ti13Zr13Nb alloy
2018, Ceramics International
Citation Excerpt :
Also oxidation was applied resulting in nanotubular layers being an excellent base for further hydroxyapatite (HAp) coatings [17], micro- and nanopatterning of the surface layer effecting in better primary and final implant stabilization [18], ion implantation with elements such as N, Ca, O, enhancing bioactivity, i.e., growth of Hap coating [19]. In particular, laser treatment can also be used for improving the alloy wear resistance [20], and deposition of phosphate coatings assuming it is still the most crucial method of introducing the bioactive behavior of Ti alloys [21]. The hydroxyapatite coatings may be deposited on the titanium substrates using many techniques.
The purpose of the research was to establish the influence of the solution composition and the electrophoretic deposition voltage on the coating homogeneity and thickness, nanohardness, adhesion, corrosion resistance and wettability. The Ti13Zr13Nb alloy was coated by the electrophoretic technique with hydroxyapatite in a solution containing 0.1, 0.2 or 0.5 g nanoHAp in 100 mL of suspension and at voltage 15, 30 or 50 V. The scanning electron and atomic force microscopies, polarization curves technique for corrosion assessment, nanoindentation and nanoscratch tests, and measurements of contact angle in simulated body fluid were performed. The obtained results revealed the complex and interrelated effects of both process determinants on the structure and properties of hydroxyapatite coatings, which were attributed to the role of the size, shape and content in suspension of hydroxyapatite particles.
Surface modification of metallic bone implants-Polymer and polymer-assisted coating for bone in-growth
2018, Fundamental Biomaterials: Metals
Metallic implants as a load bearing component are widely selected for orthopedic prosthesis due to their superiority over traditional ceramic and polymeric biomaterials. Metal-based orthopedic implants have undergone a multitude of manufacturing and surface modification techniques for enhancement of biological activities within the host site. Polymeric coatings being biocompatible in nature facilitates biological fixation of metallic implants with native extracellular matrix. Polymer and polymer-assisted coating on the metallic implants promotes the process of osseointegration while fixation related infections get reduced with these coatings. A coating enhances cell material interaction and provides structural support to the newly formed tissues. Corrosion resistance of biodegradable metallic implants (such as Mg and its alloys) can also be increased by preventing implants exposure from the body fluid with a shielding layer fabricated with suitable polymer coatings. Porous structure of the coating is an ideal condition as cells proliferate through the interconnecting porosities.
Electrophoretic deposition (EPD) of nanohydroxyapatite - nanosilver coatings on Ti13Zr13Nb alloy
2017, Ceramics International
Citation Excerpt :
Its ability to natural self-passivation and presence of the titanium dioxide on the surface reduces the risk of migration of metal ions to body fluids after implantation [8]. The weak bonding of titanium and its alloys to bone and its lack of bioactivity have resulted in a great variety of different surface modification techniques, including acidic [9,10] and alkaline treatment, nanooxidation [11], micro- and nanopatterning [12], ion implantation [13], laser treatment [14], and deposition of phosphate coatings [15]. The deposition of phosphates, usually hydroxyapatite coatings, has recently been performed using techniques such as electrophoretic deposition (EPD) [16–22], electrochemically-assisted cathodic deposition (ECAD) [23–28], or both [29]; the sputtering technique [30–32]; hydrothermal deposition followed by electrochemical seeding [33]; chemical and thermal treatment [34]; the sol-gel method [35,36]; and biomimetic (chemical) deposition [18,37].
Titanium and its alloys are the biomaterials most frequently used in medical engineering, especially as parts of orthopedic and dental implants. The surfaces of titanium and its alloys are usually modified to improve their biocompatibility and bioactivity, for example, in connection with the deposition of hydroxyapatite coatings.
The objective of the present research was to elaborate the technology of electrophoretic deposition (EPD) of nanohydroxyapatite (nanoHAp) coatings decorated with silver nanoparticles (nanoAg) and to investigate the mechanical and chemical properties of these coatings as determined by EPD voltage and the presence of nanoAg. The deposition of nanoHAp was carried out at two voltage values, 15 and 30 V. The decoration of nanoHAp coatings with nanoAg was carried out using the EPD process at a voltage value of 60 V and a deposition time of 5 min. The thickness of the undecorated coatings was found to be 2.16 and 5.14 µm for applied EPD voltages of 15- and 30-V, respectively. The release rate of silver nanoparticles into an artificial saliva solution increased with exposure time and EPD voltage. The corrosion current, between 1 and 10 nA/cm², was significantly higher for undecorated nanoHAp coatings and close to that of the substrate for decorated nanoHAp coatings. The hardness of the undecorated nanoHAp coatings obtained at 15 and 30 V of EPD voltage attained 0.2245±0.036 and 0.0661±0.008 GPa, respectively. Resistance to nanoscratching was higher for thicker coatings. The wettability angle was lower for coatings decorated with nanoAg.
Corrosion and surface modification on biocompatible metals: A review
2017, Materials Science and Engineering C
Citation Excerpt :
Despite being naturally occurring, this corrosion resistant biocompatible metal, need to undergo modifications, to enhance their useful properties, especially when used as body implants. The classification of biomaterial for implants are reliant on the main leading features, which are (i) biocompatibility of the implant (ii) the mechanical, chemical and tribological properties of the biomaterial and (iii) the health condition of the patients [45,48,59]. Thus, following sections discusses in details the causes that lead to the significance of bioimplants corrosion, some of the common types of corrosions that very frequently observed, the effect of the corrosion and its preventions through few appropriate techniques such as deposition of bioactive coatings, the formation of a surface oxide layer and several surface modifications and surface texturing methods.
Corrosion prevention in biomaterials has become crucial particularly to overcome inflammation and allergic reactions caused by the biomaterials' implants towards the human body. When these metal implants contacted with fluidic environments such as bloodstream and tissue of the body, most of them became mutually highly antagonistic and subsequently promotes corrosion. Biocompatible implants are typically made up of metallic, ceramic, composite and polymers. The present paper specifically focuses on biocompatible metals which favorably used as implants such as 316L stainless steel, cobalt-chromium-molybdenum, pure titanium and titanium-based alloys. This article also takes a close look at the effect of corrosion towards the implant and human body and the mechanism to improve it. Due to this corrosion delinquent, several surface modification techniques have been used to improve the corrosion behavior of biocompatible metals such as deposition of the coating, development of passivation oxide layer and ion beam surface modification. Apart from that, surface texturing methods such as plasma spraying, chemical etching, blasting, electropolishing, and laser treatment which used to improve corrosion behavior are also discussed in detail. Introduction of surface modifications to biocompatible metals is considered as a “best solution” so far to enhanced corrosion resistance performance; besides achieving superior biocompatibility and promoting osseointegration of biocompatible metals and alloys.
Mechanical properties and fractal analysis of the surface texture of sputtered hydroxyapatite coatings
2016, Applied Surface Science
Citation Excerpt :
Additionally, the possible release of toxic metallic ions and/or particles through corrosion or wear processes would lead to inflammatory cascades which would further diminish biocompatibility and cause tissue loss [12]. Hence, in-vivo behavior and performance of biocompatible metallic materials strongly depend on their surface properties, which can be modified by the use of various coatings [13–17]. However, obtaining medical devices as compatible with the bone as possible, and remaining their mechanical, physicochemical and bactericidal suitability is a challenge, especially in orthopaedic applications.
This aim of this work is to establish a relationship between the surface morphology and mechanical properties of hydroxyapatite coatings prepared using RF magnetron sputtering at temperatures in the range from 400 to 800 °C. The topography of the samples was scanned using atomic force microscopy, and the obtained 3D maps were analyzed using fractal methods to derive the spatial characteristics of the surfaces. X-ray photoelectron spectroscopy revealed the strong influence of the deposition temperature on the Ca/P ratio in the growing films. The coatings deposited at 600–800 °C exhibited a Ca/P ratio between 1.63 and 1.69, close to the stoichiometric hydroxyapatite (Ca/P = 1.67), which is crucial for proper osseointegration. Fourier-transform infrared spectroscopy showed that the intensity of phosphate absorption bands increased with increasing substrate temperature. Each sample exhibited well defined and sharp hydroxyapatite band at 566 cm⁻¹, although more pronounced for the coatings deposited above 500 °C. Both the hardness and elastic modulus of the coated samples decrease with increasing deposition temperature. The surface morphology strongly depends on the deposition temperature. The sample deposited at 400 °C exhibits circular cavities dug in an otherwise flat surface. At higher deposition temperatures, these cavities increase in size and start to overlap each other so that at 500 °C the surface is composed of closely packed peaks and ridges. At that point, the characteristics of the surface turns from the dominance of cavities to grains of similar size, and develops in a similar manner at higher temperatures.

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