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Reactive combinatorial synthesis and characterization of a gradient Ag–Ti oxide thin film with antibacterial properties
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)
Technical University of Catalonia.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)
2015 (English)In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 11, 503-510 p.Article in journal (Refereed) Published
Abstract [en]

The growing demand for orthopedic and dental implants has spurred researchers to develop multifunc- tional coatings, combining tissue integration with antibacterial features. A possible strategy to endow titanium (Ti) with antibacterial properties is by incorporating silver (Ag), but designing a structure with adequate Ag+ release while maintaining biocompatibility has been shown difficult. To further explore the composition–structure–property relationships between Ag and Ti, and its effects against bacteria, this study utilized a combinatorial approach to manufacture and test a single sample containing a binary Ag–Ti oxide gradient. The sample, sputter-deposited in a reactive (O2) environment using a custom-built combinatorial physical vapor deposition system, was shown to be effective against Staphylococcus aureus with viability reductions ranging from 17 to above 99%, depending on the amount of Ag+ released from its different parts. The Ag content along the gradient ranged from 35 to 62 wt.%, but it was found that structural properties such as varied porosity and degree of crystallinity, rather than the amount of incor- porated Ag, governed the Ag+ release and resulting antibacterial activity. The coating also demonstrated in vitro apatite-forming abilities, where structural variety along the sample was shown to alter the hydrophilic behavior, with the degree of hydroxyapatite deposition varying accordingly. By means of combinatorial synthesis, a single gradient sample was able to display intricate compositional and structural features affecting its biological response, which would otherwise require a series of coatings. The current findings suggest that future implant coatings incorporating Ag as an antibacterial agent could be structurally enhanced to better suit clinical requirements. 

Place, publisher, year, edition, pages
2015. Vol. 11, 503-510 p.
Keyword [en]
Combinatorial materials science, Physical vapor deposition, Antibacterial, Silver, Titanium
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Materials Science; Engineering Science with specialization in Nanotechnology and Functional Materials
URN: urn:nbn:se:uu:diva-236382DOI: 10.1016/j.actbio.2014.09.048ISI: 000347747900048PubMedID: 25281786OAI: oai:DiVA.org:uu-236382DiVA: diva2:764603
Swedish Foundation for Strategic Research

Epub 2014 Oct 02

Available from: 2014-11-19 Created: 2014-11-19 Last updated: 2015-06-30Bibliographically approved
In thesis
1. Antibacterial Strategies for Titanium Biomaterials
Open this publication in new window or tab >>Antibacterial Strategies for Titanium Biomaterials
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Titanium and titanium based alloys are widely used in dentistry and orthopedics to replace hard tissue and to mend broken bones. It has become a material of choice due to its low density, high strength, good biocompatibility and its capacity to integrate closely with the bone. Today, modern materials and surgical techniques can enable patients to live longer, and aid in maintaining or regaining mobility for a more fulfilling life. There are, however, instances where implants fail, and one of the primary causes for implant failure is infection.

This thesis deals with two possible ways of reducing or eliminating implant associated infections; TiO2 photocatalysis, where a surface can become antibacterial upon irradiation with UV light; and incorporation of silver, where a subsequent release of silver metal ions result in an antibacterial effect.

For the TiO2 photocatalysis strategy, a simple and cost effective chemical oxidation technique, using hydrogen peroxide (H2O2) and water, was used to create an active TiO2 surface on titanium substrates. This surface was shown to effectively degrade an organic model substance (rhodamine B) by generating reactive oxygen species (ROS) under UV illumination. However, it was shown that Ti-peroxy radical species remaining in the surface after the H2O2-oxidation process, rather than generation of ROS from a heterogeneous photocatalytic process, was responsible for the effect. This discovery was further exploited in a TiO2/H2O2/UV system, which demonstrated synergy effects in both rhodamine B degradation tests and in antibacterial assays.

For the silver ion release strategy, a combinatorial materials science approach was employed. Binary Ag-Ti oxide gradients were co-deposited in a reactive (O2) environment using a custom built physical vapor deposition system, and evaluated for antibacterial properties. The approach enabled synthesis and composition-structure-property evaluation unlikely to have been achieved by traditional means, and the gradient coatings demonstrated antibacterial properties against both S. aureus and S. epidermidis according to silver ion release. The release was shown to depend more on structural features, such as surface area, crystallinity and oxidation state, than on composition.

Ag-Ti oxide gradients were also evaluated under UV illumination, as Ag deposits on crystalline TiO2 can enhance photocatalytic properties. In this work, however, the TiO2 was amorphous and UV illumination caused a slight reduction in the antibacterial effect of silver ions. This was attributed to a UV-induced SOS response in the S. epidermidis bacteria.

The results of this thesis demonstrate that both TiO2 photocatalysis, or UV induced activation of Ti-peroxy radical species, as well as incorporation of silver are viable antibacterial strategies for titanium biomaterials. However, their clinical applications are still pending risk-benefit analyses of potential adverse host tissue responses. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 72 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1250
Titanium, silver, biomaterial, antibacterial, photocatalysis, hydrogen peroxide, reactive oxygen species, combinatorial materials science
National Category
Materials Engineering Medical Materials
Research subject
Engineering Science with specialization in Materials Science
urn:nbn:se:uu:diva-249181 (URN)978-91-554-9241-0 (ISBN)
Public defence
2015-06-05, Siegbahn Hall, The Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Swedish Foundation for Strategic Research
Available from: 2015-05-12 Created: 2015-04-12 Last updated: 2015-07-07

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