Special Issue "Surface Modification of Medical Implants"

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Bioactive Coatings and Biointerfaces".

Deadline for manuscript submissions: 30 November 2022 | Viewed by 10963

Special Issue Editor

Dr. Alina Vladescu
E-Mail Website
Guest Editor
Department for Advanced Surface Processing and Analysis by Vacuum Technologies, National Institute for Optoelectronics, 409 Atomistilor St., 077125 Magurele-Bucharest, Romania
Interests: surface functionalization; biocompatible and bioactive coatings; corrosion-wear resistance

Special Issue Information

Dear Colleagues,

The mechanism of implant failure is nowadays the target of intensive research, aiming to increase implant’s service life, since bone fixation devices and artificial joints comprise 44% of all medical devices. The results obtained world-wide in the last 15 years have demonstrated that the most important causes of artificial joint loosening are due to implant infection, osseointegration, degradation, friction, and abrasive wear. Thus, many efforts have been directed towards finding a solution to obtain a new implant with good mechanical, osseoconductive, and antibacterial properties, and good resistance to wear and corrosion (low friction coefficient and wear rate in the solution specific to the human body). One of prospective ways is to induce the surface modification of common medical implants in order to obtain the desired properties for clinical applications. Currently, several techniques have been developed for preparing biocompatible coatings, such as plasma spray, sol–gel, micro-arc oxidation, electrodeposition, anodization, plasma electrolytic oxidation, magnetron sputtering, and pulsed laser deposition, etc. The main goal of this Special Issue is to present the latest developments in the field of the surface modification of medical implants for enhancing the specific functionality in human aggressive media.

In particular, the topics of interest include, but are not limited to:

  • Surface science of bioactive coatings
  • Deposition and growth of biocompatible coatings
  • Coatings-based polymers
  • Surface modification by directed energy deposition (lasers, ion, or electron beams) or other techniques such as plasmas
  • Friction performance, corrosion, and wear resistance of coated load-bearing implants and/or dental implants

Dr. Alina Vladescu
Guest Editor

Manuscript Submission Information

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Published Papers (9 papers)

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Research

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Article
Electrochemical Surface Biofunctionalization of Titanium through Growth of TiO2 Nanotubes and Deposition of Zn Doped Hydroxyapatite
Coatings 2022, 12(1), 69; https://doi.org/10.3390/coatings12010069 - 07 Jan 2022
Cited by 2 | Viewed by 444
Abstract
The current research aim is to biofunctionalize pure titanium (Ti, grade IV) substrate with titania nanotubes and Zn doped hydroxyapatite-based coatings by applying a duplex electrochemical treatment, and to evaluate the influence of Zn content on the physico-chemical properties of hydroxyapatite (HAp). The [...] Read more.
The current research aim is to biofunctionalize pure titanium (Ti, grade IV) substrate with titania nanotubes and Zn doped hydroxyapatite-based coatings by applying a duplex electrochemical treatment, and to evaluate the influence of Zn content on the physico-chemical properties of hydroxyapatite (HAp). The obtained nanostructured surfaces were covered with HAp-based coatings doped with Zn in different concentrations by electrochemical deposition in pulsed galvanostatic mode. The obtained surfaces were characterized in terms of morphology, elemental and phasic composition, chemical bonds, roughness, and adhesion. The nanostructured surface consisted of titania nanotubes (NT), aligned, vertically oriented, and hollow, with an inner diameter of ~70 nm. X-ray Diffraction (XRD) analysis showed that the nanostructured surface consists of an anatase phase and some rutile peaks as a secondary phase. The morphology of all coatings consisted of ribbon like-crystals, and by increasing the Zn content the coating became denser due to the decrement of the crystals’ dimensions. The elemental and phase compositions evidenced that HAp was successfully doped with Zn through the pulsed galvanostatic method on the Ti nanostructured surfaces. Fourier Transform Infrared spectroscopy (FTIR) and XRD analysis confirmed the presence of HAp in all coatings, while the adhesion test showed that the addition of a high quantity leads to some delamination. Based on the obtained results, it can be said that the addition of Zn enhances the properties of HAp, and through proper experimental design, the concentration of Zn can be modulated to achieve coatings with tunable features. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility
Coatings 2021, 11(9), 1118; https://doi.org/10.3390/coatings11091118 - 15 Sep 2021
Viewed by 828
Abstract
Unlike the native surface of the implant material (Ti6Al4V), oxidation with H2O2 leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with [...] Read more.
Unlike the native surface of the implant material (Ti6Al4V), oxidation with H2O2 leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with H2O2, strong differences in the PHMB adsorption capability between polished and corundum-blasted surfaces appear, indicating a roughness dependence. After NaOH treatment, no such effect was observed. The wetting properties of specimens treated with either H2O2 or NaOH prior to PHMB exposure clearly varied. To unravel the nature of this interaction, widespread in silico and in vitro experiments were performed. Methods: By X-ray photoelectron spectroscopy, scanning electron microscopy, water contact angle measurements and MD simulations, we characterized the interplay between the polycationic antimicrobial agent and the implant surface. A theoretical model for PHMB micelles is tested for its wetting properties and compared to carbon contaminated TiO2. In addition, quantitation of anionic functional group equivalents, the binding properties of PHMB with blocked amino end-group, and the ability to bind chlorhexidine digluconate (CHG) were investigated. Ultimately, the capability of osteoblasts to build calcium apatite, and the activity of alkaline phosphatase on PHMB coated specimens, were determined. Results: Simulated water contact angles on carbon contaminated TiO2 surfaces and PHMB micelle models reveal little influence of PHMB on the wetting properties and point out the major influence of remaining and recovering contamination from ambient air. Testing PHMB adsorption beyond the critical micelle concentration and subsequent staining reveals an island-like pattern with H2O2 as compared to an evenly modified surface with NaOH. Both CHG and PHMB, with blocked amino end groups, were adsorbed on the treated surfaces, thus negating the significant influence of PHMB’s terminal groups. The ability of osteoblasts to produce calcium apatite and alkaline phosphatase is not negatively impaired for PHMB mass coverages up to 8 μg/specimen. Conclusion: Differences in PHMB adsorption are triggered by the number of anionic groups and carbon contaminants, both of which depend on the specimen pre-treatment. With more PHMB covering, the implant surface is protected against the capture of new contamination from the ambient air, thus building a robust antimicrobial and biocompatible surface coating. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
Zn-Doped CaP-Based Coatings on Ti–6Al–4V and Ti–6Al–7Nb Alloys Prepared by Magnetron Sputtering: Controllable Biodegradation, Bacteriostatic, and Osteogenic Activities
Coatings 2021, 11(7), 809; https://doi.org/10.3390/coatings11070809 - 03 Jul 2021
Cited by 5 | Viewed by 1112
Abstract
New TiNb-based alloys, such as Ti–6Al–7Nb, are currently being studied around the world as an alternative to other Ti alloys, e.g., instead of Ti–6Al–4V. We conducted a pilot study where thin (approximately 1.2 micron) CaP coatings containing low doses of Zn2+ (0.4–0.8 [...] Read more.
New TiNb-based alloys, such as Ti–6Al–7Nb, are currently being studied around the world as an alternative to other Ti alloys, e.g., instead of Ti–6Al–4V. We conducted a pilot study where thin (approximately 1.2 micron) CaP coatings containing low doses of Zn2+ (0.4–0.8 wt.%) were prepared by the radio frequency magnetron sputtering (RFMS) of Zn-hydroxyapatite (HA) target on Ti–6Al–4V and Ti–6Al–7Nb substrates and investigated their physicochemical properties, in vitro solubility, cytotoxicity, and antibacterial and osteogenic activities. The thickness of the obtained coatings was approximately 1.2–1.3 microns. Zn substitution did not result in roughness or structural or surface changes in the amorphous CaP coatings. The distributions of Ca, P, and Zn were homogeneous across the film thickness as shown by the EDX mapping of these elements. Zn doping of CaP coatings on both types of Ti-based alloys statistically influenced the results of the scratch-test. However, obtained values are satisfactory to use Zn-CaP coatings on biomedical implants. Increased Zn2+ release vs. tapered output of Ca and phosphate ions occurred during 5 weeks of an in vitro immersion test in 0.9% NaCl solution. Ti–6Al–7Nb alloy, unlike Ti–6Al–4V, promoted more linear biodegradation of CaP coatings in vitro. As a result, CaP-based surfaces on Ti–6Al–7Nb, compared with on Ti–6Al–4V alloy, augmented the total areas of Alizarin red staining in a 21-day culture of human adipose-derived mesenchymal stem cells in a statistically significant manner. Moreover, Zn–CaP coatings statistically reduced leukemic Jurkat T cell survival within 48 h of in vitro culture. Along with the higher solubility of the Zn–CaP surface, a greater reduction (4- to 5.5-fold) in Staphylococcus aureus growth was observed in vitro when 7-day extracts of the coatings were added into the microbial culture. Hence, Zn–CaP-coated Ti–6Al–7Nb alloy with controllable biodegradation as prepared by RFMS is a prospective material suitable for bone applications in cases where there is a risk of bacterial contamination with severe consequences, for example, in leukemic patients. Further research is needed to closely investigate the mechanical features and pathways of their solubility and antimicrobial, antitumor, and osteogenic activities. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
Tunable Microstructure and Morphology of the Self-Assembly Hydroxyapatite Coatings on ZK60 Magnesium Alloy Substrates Using Hydrothermal Methods
Coatings 2021, 11(1), 8; https://doi.org/10.3390/coatings11010008 - 24 Dec 2020
Cited by 2 | Viewed by 802
Abstract
Hydroxyapatite coatings have been widely used to improve the corrosion resistance of biodegradable magnesium alloys. In this paper, in order to manufacture the ideal hydroxyapatite (HA) coating on the ZK60 magnesium substrate by hydrothermal method, formation mechanism of enhanced hydroxyapatite (HA) coatings, influence [...] Read more.
Hydroxyapatite coatings have been widely used to improve the corrosion resistance of biodegradable magnesium alloys. In this paper, in order to manufacture the ideal hydroxyapatite (HA) coating on the ZK60 magnesium substrate by hydrothermal method, formation mechanism of enhanced hydroxyapatite (HA) coatings, influence of pH values of the precursor solution on the HA morphology, corrosion resistance and cytotoxicity of HA coatings have been investigated. Results show that the growth pattern of the HA is influenced by the local pH value. HA has a preferential c-axis and higher crystallinity in the alkaline environment developing a nanorod-like structure, while in acid and neutral environments it has a preferential growth along the a(b)-plane with a lower crystallinity, developing a nanosheet-like structure. The different morphology and microstructure lead to different degradation behavior and performance of HA coatings. Immersion and electrochemical tests show that the neutral environment promote formation of HA coatings with high corrosion resistance. The cell culture experiments confirm that the enhanced corrosion resistance assure the biocompatibility of the substrate-coating system. In general, the HA coating prepared in neutral environment shows great potential in surface modification of magnesium alloys. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
In Vitro Corrosion of Titanium Nitride and Oxynitride-Based Biocompatible Coatings Deposited on Stainless Steel
Coatings 2020, 10(8), 710; https://doi.org/10.3390/coatings10080710 - 22 Jul 2020
Cited by 12 | Viewed by 1451
Abstract
The reactive cathodic arc deposition technique was used to produce Ti nitride and oxynitride coatings on 304 stainless steel substrates (SS). Both mono (SS/TiN, SS/TiNO) and bilayer coatings (SS/TiN/TiNO and SS/TiNO/TiN) were investigated in terms of elemental and phase composition, microstructure, grain size, [...] Read more.
The reactive cathodic arc deposition technique was used to produce Ti nitride and oxynitride coatings on 304 stainless steel substrates (SS). Both mono (SS/TiN, SS/TiNO) and bilayer coatings (SS/TiN/TiNO and SS/TiNO/TiN) were investigated in terms of elemental and phase composition, microstructure, grain size, morphology, and roughness. The corrosion behavior in a solution consisting of 0.10 M NaCl + 1.96 M H2O2 was evaluated, aiming for biomedical applications. The results showed that the coatings were compact, homogeneously deposited on the substrate, and displaying rough surfaces. The XRD analysis indicated that both mono and bilayer coatings showed only cubic phases with (111) and (222) preferred orientations. The highest crystallinity was shown by the SS/TiN coating, as indicated also by the largest grain size of 23.8 nm, which progressively decreased to 16.3 nm for the SS/TiNO monolayer. The oxynitride layers exhibited the best in vitro corrosion resistance either as a monolayer or as a top layer in the bilayer structure, making them a good candidate for implant applications. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
In Vitro Corrosion and Tribocorrosion Performance of Biocompatible Carbide Coatings
Coatings 2020, 10(7), 654; https://doi.org/10.3390/coatings10070654 - 07 Jul 2020
Cited by 2 | Viewed by 1248
Abstract
The present study aims to explain the corrosion and the tribocorrosion performance in simulated conditions of the human body by the level of stress, adhesion of coating to substrate, roughness, and hardness. The coatings were synthesized by the cathodic arc evaporation method on [...] Read more.
The present study aims to explain the corrosion and the tribocorrosion performance in simulated conditions of the human body by the level of stress, adhesion of coating to substrate, roughness, and hardness. The coatings were synthesized by the cathodic arc evaporation method on 316L stainless steel substrates to be used for load bearing implants. Structure, elemental, and phase compositions were studied by means of energy dispersive spectrometry and X-ray diffraction, respectively. The grain size and strain of the coatings were determined by the Williamson–Hall plot method. Tests on hardness, adhesion, roughness, and electrochemical behavior in 0.9% NaCl solution at 37 ± 0.5 °C were carried out. Tribocorrosion performances, evaluated by measuring the friction coefficient and wear rate, were conducted in 0.9% NaCl solution using the pin on disc method at 37 ± 0.5 °C. TiC and ZrC exhibited a (111) preferred orientation, while TiNbC had a (200) orientation and the smallest crystallite size (8.1 nm). TiC was rougher than ZrC and TiNbC; the lowest roughness was found for TiNbC coatings. The highest hardness and adhesion values were found for TiNbC, followed by TiC and the ZrC. All coatings improved the corrosion resistance of 316L steels, but TiNbC showed the best corrosion behavior. TiNbC had the lowest friction coefficient (1.6) and wear rate (0.99 × 10−5 mm3·N−1∙m−1) values, indicating the best tribocorrosive performance in 0.9% NaCl at 37 ± 0.5 °C. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
Comparison of the Clinical Results of Identically Designed Total Knee Prostheses with Different Surface Roughnesses
Coatings 2020, 10(5), 486; https://doi.org/10.3390/coatings10050486 - 19 May 2020
Viewed by 1236
Abstract
The purpose of this study was to investigate the effects of the undersurface roughness of total knee prosthesis on clinical outcomes. We compared the clinical and radiological outcomes and prosthesis survivals in patients who underwent total knee arthroplasty using prosthesis with identical designs [...] Read more.
The purpose of this study was to investigate the effects of the undersurface roughness of total knee prosthesis on clinical outcomes. We compared the clinical and radiological outcomes and prosthesis survivals in patients who underwent total knee arthroplasty using prosthesis with identical designs but different surface roughness (average surface roughnesses (Ra), 5.0 μm vs. 11.6 μm). The results showed that the knee prostheses with a more roughened undersurface (Ra = 11.6 μm) produced significantly better functional results and enhanced prosthesis survival. The difference in surface roughness was associated with incidence of osteolysis and loosening at the tibial baseplate, but not at the femoral component. Overall, our results provided significant evidence that the use of roughened undersurface of tibial baseplate would be a way to prevent aseptic loosening. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Article
In Vitro Activity Assays of Sputtered HAp Coatings with SiC Addition in Various Simulated Biological Fluids
Coatings 2019, 9(6), 389; https://doi.org/10.3390/coatings9060389 - 15 Jun 2019
Cited by 10 | Viewed by 1979
Abstract
Considering the requirements of medical implantable devices, it is pointed out that biomaterials should play a more sophisticated, longer-term role in the customization and optimization of the material–tissue interface in order to ensure the best long-term clinical outcomes. The aim of this contribution [...] Read more.
Considering the requirements of medical implantable devices, it is pointed out that biomaterials should play a more sophisticated, longer-term role in the customization and optimization of the material–tissue interface in order to ensure the best long-term clinical outcomes. The aim of this contribution was to assess the performance of silicon carbide–hydroxyapatite in various simulated biological fluids (Dulbecco’s modified Eagle’s medium (DMEM), simulated body fluid (SBF), and phosphate buffer solution (PBS)) through immersion assays for 21 days at 37 ± 0.5 °C and to evaluate the electrochemical behavior. The coatings were prepared on Ti6Al4V alloy substrates by magnetron sputtering method using two cathodes made of hydroxyapatite and silicon carbide (SiC). After immersion assays the coating’s surface was analyzed in terms of morphology, chemical and phase composition, and chemical bonds. According to the electrochemical behavior in the media investigated at 37 ± 0.5 °C, SiC addition inhibits the dissolution of the hydroxyapatite in DMEM acellular media. Furthermore, after adding SiC, the slow degradation of hydroxyapatite in PBS and SBF media as well as biomineralization in DMEM were observed. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Other

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Systematic Review
Role of Stem Cells in Augmenting Dental Implant Osseointegration: A Systematic Review
Coatings 2021, 11(9), 1035; https://doi.org/10.3390/coatings11091035 - 27 Aug 2021
Cited by 5 | Viewed by 702
Abstract
Dental implants are a widely used treatment modality for oral rehabilitation. Implant failures can be a result of many factors, with poor osseointegration being the main culprit. The present systematic review aimed to assess the effect of stem cells on the osseointegration of [...] Read more.
Dental implants are a widely used treatment modality for oral rehabilitation. Implant failures can be a result of many factors, with poor osseointegration being the main culprit. The present systematic review aimed to assess the effect of stem cells on the osseointegration of dental implants. An electronic search of the MEDLINE, LILACS, and EMBASE databases was conducted. We examined quantitative preclinical studies that reported on the effect of mesenchymal stem cells on bone healing after implant insertion. Eighteen studies that fulfilled the inclusion criteria were included. Various surface modification strategies, sites of placement, and cell origins were analyzed. The majority of the selected studies showed a high risk of bias, indicating that caution must be exercised in their interpretation. All the included studies reported that the stem cells used with graft material and scaffolds promoted osseointegration with higher levels of new bone formation. The mesenchymal cells attached to the implant surface facilitated the expression of bio-functionalized biomaterial surfaces, to boost bone formation and osseointegration at the bone–implant interfaces. There was a promotion of osteogenic differentiation of human mesenchymal cells and osseointegration of biomaterial implants, both in vitro and in vivo. These results highlight the significance of biomodified implant surfaces that can enhance osseointegration. These innovations can improve the stability and success rate of the implants used for oral rehabilitation. Full article
(This article belongs to the Special Issue Surface Modification of Medical Implants)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Tentative Title:  Preparation and biofunctionalization of a novel biocompatible alloy used for bone implants
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