Special Issue "Physical Vapor Deposited Biomedical Coatings"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (30 December 2020).

Special Issue Editors

Dr. George E. Stan
E-Mail Website
Guest Editor
National Institute of Materials Physics, RO-077125, Magurele-Ilfov, Romania
Interests: biomaterials; magnetron sputtering deposition; thin films and protective coatings; thermal processing; in vitro and in vivo testing; structural characterization techniques
Dr. Bryan W. Stuart
E-Mail
Guest Editor
The University of Oxford, Department of Materials, Parks Road, OX1 3PH, Oxford, UK
Interests: material characterisation; biomaterials; phosphate glass; coatings; RF magnetron sputtering; wearable and flexible electronics; roll to roll/thermal evaporation

Special Issue Information

Dear Colleagues,

As research and development into medical devices reaches an all-time high, surface functionalisation through less invasive, low dimensional thin-film coatings is at the forefront of optimising bio-integration, bioactivation, and biomechanics. In the last decades, physical vapour deposition (PVD) technologies such as magnetron sputtering, evaporation, pulsed laser deposition, etc. have gained attraction for their diverse capabilities in blending and manufacturing highly adhesive, novel materials with minimally invasive thicknesses from angstroms to the micron scale. Medical devices of all kinds benefit from functional surface layers, including but not limited to lubricating coatings on wear-prone load-bearing implants, antimicrobial layers, wound dressings, bioresorbable smart pills, angiogenic surfaces, cardiovascular stents, or biomimetic orthopaedic integration layers. PVD modified implant surfaces benefit from enhanced bioactivity, leading to advantageous cell–surface interactions to assist in regenerating tissue.

It has long been the opinion of the industrial community that technologies based on thermal spray technologies (e.g., plasma spray, flame spray, detonation spray, cold spray, high-velocity atmospheric spray, high-velocity oxy-fuel spray, and high-velocity suspension flame spraying) and solution-based methods (e.g., sol–gel, solution castings) provide high through-put capabilities and low start-up costs suitable for commercial scale manufacturing. However, as the precision, versatility, scale, and accessibility of standardised PVD systems grows, the medical device industry will seek mature materials research for the next generation of functional layers with long-term reliability and high success rates.

This Special Issue will endeavour to present current and progressive research into PVD technologies applied to medical coatings with a distinct emphasis on the following scopes:

  • Medical devices based on sputtering, induction/thermal/e-beam evaporation, cathodic arc deposition, pulsed laser/electron beam deposition or other vapour deposition techniques;
  • Glasses and ceramics (bioactive, bioresorbable and wear-resistant coatings in orthopaedics, muscular and cardio-vascular applications);
  • Surface functionalisation using vapour deposition sources, including e-beam treatment or plasma treatment;
  • Mechanical and materials characterisation of PVD layers. Recent progression in methodologies and next generation testing standards;
  • PVD scale-up towards commercial manufacturing and coating applied to additive manufactured components and porous structures;
  • In vitro and in vivo studies of coated implant materials from polymers, metals and ceramics;
  • Modelling and/or theoretical understanding of atomic interactions fundamental to PVD processing as applied to deposition of medical coatings;
  • Presentation of experimental methodologies in thin-film composites via material blends or multilayers.

Dr. George E Stan
Dr. Bryan W. Stuart
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • physical vapour deposition
  • thin-films
  • medical devices
  • bioactivity
  • biomimicry

Published Papers (8 papers)

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Editorial

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Editorial
Physical Vapour Deposited Biomedical Coatings
Coatings 2021, 11(6), 619; https://doi.org/10.3390/coatings11060619 - 21 May 2021
Viewed by 313
Abstract
This Special Issue was devoted to developments made in Physical Vapour Deposited (PVD) biomedical coatings for various healthcare applications. The scrutinized PVD methods were Radio-Frequency Magnetron Sputtering (RF-MS), Cathodic Arc Evaporation, Pulsed Electron Deposition and its variants, Pulsed Laser Deposition, and Matrix Assisted [...] Read more.
This Special Issue was devoted to developments made in Physical Vapour Deposited (PVD) biomedical coatings for various healthcare applications. The scrutinized PVD methods were Radio-Frequency Magnetron Sputtering (RF-MS), Cathodic Arc Evaporation, Pulsed Electron Deposition and its variants, Pulsed Laser Deposition, and Matrix Assisted Pulsed Laser Evaporation (MAPLE), due to their great promise especially in the dentistry and orthopaedics. These methods have yet to gain traction for industrialization and large-scale application in biomedicine. A new generation of implant coatings can be made available by the (1) incorporation of organic moieties (e.g., proteins, peptides, enzymes) into thin films by innovative methods such as combinatorial MAPLE, (2) direct coupling of therapeutic agents with bioactive glasses or ceramics within substituted or composite layers via RF-MS, or (3) by innovation in high energy deposition methods such as arc evaporation or pulsed electron beam methods. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)

Research

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Article
The Beneficial Mechanical and Biological Outcomes of Thin Copper-Gallium Doped Silica-Rich Bio-Active Glass Implant-Type Coatings
Coatings 2020, 10(11), 1119; https://doi.org/10.3390/coatings10111119 - 20 Nov 2020
Cited by 3 | Viewed by 623
Abstract
Silica-based bioactive glasses (SBG) hold great promise as bio-functional coatings of metallic endo-osseous implants, due to their osteoproductive potential, and, in the case of designed formulations, suitable mechanical properties and antibacterial efficacy. In the framework of this study, the FastOs®BG alkali-free [...] Read more.
Silica-based bioactive glasses (SBG) hold great promise as bio-functional coatings of metallic endo-osseous implants, due to their osteoproductive potential, and, in the case of designed formulations, suitable mechanical properties and antibacterial efficacy. In the framework of this study, the FastOs®BG alkali-free SBG system (mol%: SiO2—38.49, CaO—36.07, P2O5—5.61, MgO—19.24, CaF2—0.59), with CuO (2 mol%) and Ga2O3 (3 mol%) antimicrobial agents, partially substituting in the parent system CaO and MgO, respectively, was used as source material for the fabrication of intentionally silica-enriched implant-type thin coatings (~600 nm) onto titanium (Ti) substrates by radio-frequency magnetron sputtering. The physico-chemical and mechanical characteristics, as well as the in vitro preliminary cytocompatibility and antibacterial performance of an alkali-free silica-rich bio-active glass coating designs was further explored. The films were smooth (RRMS < 1 nm) and hydrophilic (water contact angle of ~65°). The SBG coatings deposited from alkali-free copper-gallium co-doped FastOs®BG-derived exhibited improved wear performance, with the coatings eliciting a bonding strength value of ~53 MPa, Lc3 critical load value of ~4.9 N, hardness of ~6.1 GPa and an elastic modulus of ~127 GPa. The Cu and Ga co-doped SBG layers had excellent cytocompatibility, while reducing after 24 h the Staphylococcus aureus bacterial development with 4 orders of magnitude with respect to the control situations (i.e., nutritive broth and Ti substrate). Thereby, such SBG constructs could pave the road towards high-performance bio-functional coatings with excellent mechanical properties and enhanced biological features (e.g., by coupling cytocompatibility with antimicrobial properties), which are in great demand nowadays. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Article
The Surface Characterisation of Polyetheretherketone (PEEK) Modified via the Direct Sputter Deposition of Calcium Phosphate Thin Films
Coatings 2020, 10(11), 1088; https://doi.org/10.3390/coatings10111088 - 13 Nov 2020
Cited by 1 | Viewed by 716
Abstract
Polyetheretherketone (PEEK) has emerged as the material of choice for spinal fusion devices, replacing conventional materials such as titanium and its alloys due to its ability to easily overcome a lot of the limitations of traditional metallic biomaterials. However, one of the major [...] Read more.
Polyetheretherketone (PEEK) has emerged as the material of choice for spinal fusion devices, replacing conventional materials such as titanium and its alloys due to its ability to easily overcome a lot of the limitations of traditional metallic biomaterials. However, one of the major drawbacks of this material is that it is not osteoinductive, nor osteoconductive, preventing direct bone apposition. One way to overcome this is through the modification of the PEEK with bioactive calcium phosphate (CaP) materials, such as hydroxyapatite (HA–Ca10(PO4)6(OH)2). RF magnetron sputtering has been shown to be a particularly useful technique for the deposition of CaP coatings due to the ability of the technique to provide greater control of the coating’s properties. The work undertaken here involved the deposition of HA directly onto PEEK via RF magnetron at a range of deposition times between 10–600 min to provide more bioactive surfaces. The surfaces produced have been extensively characterised using X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), stylus profilometry, and Time of Flight Secondary Ion Mass Spectrometry (ToFSIMS). XPS results indicated that both Ca and P had successfully deposited onto the surface, albeit with low Ca/P ratios of around 0.85. ToFSIMS analysis indicated that Ca and P had been homogeneously deposited across all the surfaces. The SEM results showed that the CaP surfaces produced were a porous micro-/nano-structured lattice network and that the deposition rate influenced the pore area, pore diameter and number of pores. Depth profiling, using ToFSIMS, highlighted that Ca and P were embedded into the PEEK matrix up to a depth of around 1.21 µm and that the interface between the CaP surface and PEEK substrate was an intermixed layer. In summary, the results highlighted that RF magnetron sputtering can deliver homogenous CaP lattice-like surfaces onto PEEK in a direct, one-step process, without the need for any interlayers, and provides a basis for enhancing the potential bioactivity of PEEK. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Article
In Vivo Assessment of Bone Enhancement in the Case of 3D-Printed Implants Functionalized with Lithium-Doped Biological-Derived Hydroxyapatite Coatings: A Preliminary Study on Rabbits
Coatings 2020, 10(10), 992; https://doi.org/10.3390/coatings10100992 - 17 Oct 2020
Cited by 2 | Viewed by 804
Abstract
We report on biological-derived hydroxyapatite (HA, of animal bone origin) doped with lithium carbonate (Li-C) and phosphate (Li-P) coatings synthesized by pulsed laser deposition (PLD) onto Ti6Al4V implants, fabricated by the additive manufacturing (AM) technique. After being previously validated by in vitro cytotoxicity [...] Read more.
We report on biological-derived hydroxyapatite (HA, of animal bone origin) doped with lithium carbonate (Li-C) and phosphate (Li-P) coatings synthesized by pulsed laser deposition (PLD) onto Ti6Al4V implants, fabricated by the additive manufacturing (AM) technique. After being previously validated by in vitro cytotoxicity tests, the Li-C and Li-P coatings synthesized onto 3D Ti implants were preliminarily investigated in vivo, by insertion into rabbits’ femoral condyles. The in vivo experimental model for testing the extraction force of 3D metallic implants was used for this study. After four and nine weeks of implantation, all structures were mechanically removed from bones, by tensile pull-out tests, and coatings’ surfaces were investigated by scanning electron microscopy. The inferred values of the extraction force corresponding to functionalized 3D implants were compared with controls. The obtained results demonstrated significant and highly significant improvement of functionalized implants’ attachment to bone (p-values ≤0.05 and ≤0.00001), with respect to controls. The correct placement and a good integration of all 3D-printed Ti implants into the surrounding bone was demonstrated by performing computed tomography scans. This is the first report in the dedicated literature on the in vivo assessment of Li-C and Li-P coatings synthesized by PLD onto Ti implants fabricated by the AM technique. Their improved mechanical characteristics, along with a low fabrication cost from natural, sustainable resources, should recommend lithium-doped biological-derived materials as viable substitutes of synthetic HA for the fabrication of a new generation of metallic implant coatings. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Article
Improvement of CoCr Alloy Characteristics by Ti-Based Carbonitride Coatings Used in Orthopedic Applications
Coatings 2020, 10(5), 495; https://doi.org/10.3390/coatings10050495 - 22 May 2020
Cited by 1 | Viewed by 947
Abstract
The response of the human body to implanted biomaterials involves several complex reactions. The potential success of implantation depends on the knowledge of the interaction between the biomaterials and the corrosive environment prior to the implantation. Thus, in the present study, the in [...] Read more.
The response of the human body to implanted biomaterials involves several complex reactions. The potential success of implantation depends on the knowledge of the interaction between the biomaterials and the corrosive environment prior to the implantation. Thus, in the present study, the in vitro corrosion behavior of biocompatible carbonitride-based coatings are discussed, based on microstructure, mechanical properties, roughness and morphology. TiCN and TiSiCN coatings were prepared by the cathodic arc deposition method and were analyzed as a possible solution for load bearing implants. It was found that both coatings have an almost stoichiometric structure, being solid solutions, which consist of a mixture of TiC and TiN, with a face-centered cubic (FCC) structure. The crystallite size decreased with the addition of Si into the TiCN matrix: the crystallite size of TiCN was 16.4 nm, while TiSiCN was 14.6 nm. The addition of Si into TiCN resulted in smaller Ra roughness values, indicating a beneficial effect of Si. All investigated surfaces have positive skewness, being adequate for the load bearing implants, which work in a corrosive environment. The hardness of the TiCN coating was 36.6 ± 2.9 GPa and was significantly increased to 47.4 ± 1 GPa when small amounts of Si were added into the TiCN layer structure. A sharp increase in resistance to plastic deformation (H3/E2 ratio) from 0.63 to 1.1 was found after the addition of Si into the TiCN matrix. The most electropositive value of corrosion potential was found for the TiSiCN coating (−14 mV), as well as the smallest value of corrosion current density (49.6 nA cm2), indicating good corrosion resistance in 90% DMEM + 10% FBS, at 37 ± 0.5 °C. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Article
Production of High Silicon-Doped Hydroxyapatite Thin Film Coatings via Magnetron Sputtering: Deposition, Characterisation, and In Vitro Biocompatibility
Coatings 2020, 10(2), 190; https://doi.org/10.3390/coatings10020190 - 23 Feb 2020
Cited by 3 | Viewed by 1601
Abstract
In recent years, it has been found that small weight percent additions of silicon to HA can be used to enhance the initial response between bone tissue and HA. A large amount of research has been concerned with bulk materials, however, only recently [...] Read more.
In recent years, it has been found that small weight percent additions of silicon to HA can be used to enhance the initial response between bone tissue and HA. A large amount of research has been concerned with bulk materials, however, only recently has the attention moved to the use of these doped materials as coatings. This paper focusses on the development of a co-RF and pulsed DC magnetron sputtering methodology to produce a high percentage Si containing HA (SiHA) thin films (from 1.8 to 13.4 wt.%; one of the highest recorded in the literature to date). As deposited thin films were found to be amorphous, but crystallised at different annealing temperatures employed, dependent on silicon content, which also lowered surface energy profiles destabilising the films. X-ray photoelectron spectroscopy (XPS) was used to explore the structure of silicon within the films which were found to be in a polymeric (SiO2; Q4) state. However, after annealing, the films transformed to a SiO44−, Q0, state, indicating that silicon had substituted into the HA lattice at higher concentrations than previously reported. A loss of hydroxyl groups and the maintenance of a single-phase HA crystal structure further provided evidence for silicon substitution. Furthermore, a human osteoblast cell (HOB) model was used to explore the in vitro cellular response. The cells appeared to prefer the HA surfaces compared to SiHA surfaces, which was thought to be due to the higher solubility of SiHA surfaces inhibiting protein mediated cell attachment. The extent of this effect was found to be dependent on film crystallinity and silicon content. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Review

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Review
Biomimetic Coatings Obtained by Combinatorial Laser Technologies
Coatings 2020, 10(5), 463; https://doi.org/10.3390/coatings10050463 - 09 May 2020
Cited by 4 | Viewed by 2178
Abstract
The modification of implant devices with biocompatible coatings has become necessary as a consequence of premature loosening of prosthesis. This is caused mainly by chronic inflammation or allergies that are triggered by implant wear, production of abrasion particles, and/or release of metallic ions [...] Read more.
The modification of implant devices with biocompatible coatings has become necessary as a consequence of premature loosening of prosthesis. This is caused mainly by chronic inflammation or allergies that are triggered by implant wear, production of abrasion particles, and/or release of metallic ions from the implantable device surface. Specific to the implant tissue destination, it could require coatings with specific features in order to provide optimal osseointegration. Pulsed laser deposition (PLD) became a well-known physical vapor deposition technology that has been successfully applied to a large variety of biocompatible inorganic coatings for biomedical prosthetic applications. Matrix assisted pulsed laser evaporation (MAPLE) is a PLD-derived technology used for depositions of thin organic material coatings. In an attempt to surpass solvent related difficulties, when different solvents are used for blending various organic materials, combinatorial MAPLE was proposed to grow thin hybrid coatings, assembled in a gradient of composition. We review herein the evolution of the laser technological process and capabilities of growing thin bio-coatings with emphasis on blended or multilayered biomimetic combinations. These can be used either as implant surfaces with enhanced bioactivity for accelerating orthopedic integration and tissue regeneration or combinatorial bio-platforms for cancer research. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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Review
The Pulsed Electron Deposition Technique for Biomedical Applications: A Review
Coatings 2020, 10(1), 16; https://doi.org/10.3390/coatings10010016 - 25 Dec 2019
Cited by 6 | Viewed by 1358
Abstract
The “pulsed electron deposition” (PED) technique, in which a solid target material is ablated by a fast, high-energy electron beam, was initially developed two decades ago for the deposition of thin films of metal oxides for photovoltaics, spintronics, memories, and superconductivity, and dielectric [...] Read more.
The “pulsed electron deposition” (PED) technique, in which a solid target material is ablated by a fast, high-energy electron beam, was initially developed two decades ago for the deposition of thin films of metal oxides for photovoltaics, spintronics, memories, and superconductivity, and dielectric polymer layers. Recently, PED has been proposed for use in the biomedical field for the fabrication of hard and soft coatings. The first biomedical application was the deposition of low wear zirconium oxide coatings on the bearing components in total joint replacement. Since then, several works have reported the manufacturing and characterization of coatings of hydroxyapatite, calcium phosphate substituted (CaP), biogenic CaP, bioglass, and antibacterial coatings on both hard (metallic or ceramic) and soft (plastic or elastomeric) substrates. Due to the growing interest in PED, the current maturity of the technology and the low cost compared to other commonly used physical vapor deposition techniques, the purpose of this work was to review the principles of operation, the main applications, and the future perspectives of PED technology in medicine. Full article
(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)
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