Special Issue "Physical Vapor Deposited Biomedical Coatings"

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

Deadline for manuscript submissions: 30 December 2020.

Special Issue Editors

Dr. George E. Stan
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

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 1600 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 (4 papers)

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Research

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Open AccessArticle
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
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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Open AccessFeature PaperArticle
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
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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Open AccessReview
Biomimetic Coatings Obtained by Combinatorial Laser Technologies
Coatings 2020, 10(5), 463; https://doi.org/10.3390/coatings10050463 - 09 May 2020
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)
Open AccessFeature PaperReview
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 1
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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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.

Planned paper 1:

The Surface Characterisation of Polyetheretherketone (Peek) Modified Via The Sputter Deposition of Calcium Phosphate Thin Films

L. Robinson, J. Acheson, B.J. Meenan and A.R. Boyd*

Nanotechnology and Integrated Bioengineering Centre (NIBEC), School of Engineering, University of Ulster, Shore Road, Newtownabbey, Co. Antrim, BT37 0QB. Northern Ireland (UK)

Abstract: In recent year’s synthetic polymers, such as Polyether ether ketone (PEEK) has emerged as the material of choice for spinal fusion devices, replacing conventional materials such as titanium and its alloys. This is due to the fact that PEEK can easily overcome a lot of the limitations of traditional metallic biomaterials due to its elastic modulus being very close to that of bone, it does not cause imaging artefacts, it can be more easily processed (such as by additive manufacturing approaches, namely 3D printing), it doesn’t degrade in vivo, and is biocompatible. However, the major limitations of this material, especially within orthopaedics, is that it is not osteoinductive nor osteoconductive, leading to delayed or weak bone-to-implant integration.

One way to overcome these limitations is through the modification of the PEEK implant with bioactive calcium phosphate (CaP) materials, such as hydroxyapatite (HA - Ca10(PO4)6(OH)2). Several methods have also been investigated as a means to deposit a bioactive HA coating onto PEEK, namely plasma spraying, ion bean assisted deposition (IBAD), and radio frequency (RF) magnetron sputtering. Of these techniques, 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 and improved biological performance.

The work undertaken here involved the deposition of HA onto PEEK via RF magnetron sputtering using at a low discharge power level (<200 Watts), in order to provide a bioactive surface that would not damage the underlying substrate, provided coatings of a consistent quality and didn’t require any additional post deposition processing steps, such as annealing. 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).

 

Planned paper 2:

Combinatorial Laser Technologies for Controlled Growth of Blended and Multilayered Biocoatings

 E. Axente1, L.E. Sima2, F. Sima1*

1Center for Advanced Laser Technologies (CETAL), National Institute for Laser, Plasma and Radiation Physics (INFLPR), 409 Atomistilor, Magurele 077125, Romania

2Institute of Biochemistry of the Romanian Academy, 296 Splaiul Independentei, Bucharest 060031, Romania

Abstract: The need to modify implant devices with biocompatible coatings has emerged following observed premature loosening of prosthesis caused mainly by chronic inflammation or allergies. These are triggered by implant wear, production of abrasion particles and/or release of metallic ions from the implantable device surface. Function of 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 vapour deposition technology that has been successfully applied for a large variety of biocompatible inorganic coatings for biomedical prosthetic applications. In particular, materials with complex stoichiometry can be ablated in vacuum from solid targets by high energetic pulsed laser beams and deposited on front facing collectors as a thin coating. The process is additive and the coating thickness is precisely controlled by number of applied laser pulses. Matrix assisted pulsed laser evaporation (MAPLE) is a PLD-derived technology applied for organic materials. To the difference of PLD, the laser beam, used at very low energies, interacts with a cryogenic target obtained from solution of a solute compound dissolved in appropriate solvent. During irradiation in a vacuum chamber, the solvent is vaporised and removed while the solute, as delicate as a protein, is transferred on the collector, preserving conformation and biological activity. During MAPLE deposition the biomolecules are protected from laser irradiation within molecular cages formed by the frozen solvent. More recently, the two laser based techniques, PLD and MAPLE, have been employed together in a two-step process for growing inorganic-organic layers in order to increase functionality of surfaces proposed for implant coatings. In an attempt to surpass solvent related difficulties that chemical methods meet, when different solvents are used for blending various organic materials in thin coating configurations, combinatorial MAPLE (C-MAPLE) was proposed and applied to grow thin blended coatings of controllable thicknesses, in a precise geometrical configuration. Specifically, by employing two synchronised laser beams, two different targets are simultaneously vaporised and the blended materials assembled in a gradient of composition tailored by the target-collector distance. We review herein the laser process capabilities of growing thin biocoatings with emphasis on blended or multilayered biomimetic combinations that can be used as implant surfaces with enhanced bioactivity for accelerating orthopaedic integration and tissue regeneration.

Planned paper 3:

Improvement of CoCr alloy characteristics by Ti based carbonitrides coatings used in orthopaedic applications 

Alina Vladescu

National Institute for Optoelectronics (INOE2000)

 

 

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