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Stability and prospect of UV/H2O2 activated titania films for biomedical use
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)
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)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)
2013 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 285, no Part B, 317-323 p.Article in journal (Refereed) Published
Abstract [en]

Biomedical implants and devices that penetrate soft tissue are highly susceptible to infection, but also accessible for UV induced decontamination through photocatalysis if coated with suitable surfaces. As an on-demand antibacterial strategy, photocatalytic surfaces should be able to maintain their antibacterial properties over repeated activation. This study evaluates the surface properties and photocatalytic performance of titania films obtained by H2O2-oxidation and heat treatment of Ti and Ti-6Al-4V substrates, as well as the prospect of assisting photocatalytic reactions with H2O2 for improved efficiency. H2O2-oxidation generated a nanoporous coating, and subsequent heat treatment above 500 °C resulted in anatase formation. Tests using photo-assisted degradation of rhodamine B showed that prior to heat treatment, an initially high photocatalytic activity (PCA) of H2O2-oxidized substrates decayed significantly with repeated testing. Heat treating the samples at 600 °C resulted in stable yet lower PCA. Addition of 3% H2O2 during the photo-assisted reaction led to a substantial increase in PCA due to synergetic effects at the surface and H2O2 photolysis, the effect being most notable for non-heat treated samples. Both heat treated and non-heat treated samples showed stable PCA through repeated tests with H2O2-assisted photocatalysis, indicating that the combination of H2O2-oxidized titania films, UV light and added H2O2 can improve efficiency of these photocatalytic surfaces.

Place, publisher, year, edition, pages
2013. Vol. 285, no Part B, 317-323 p.
Keyword [en]
TiO2, Heat treatment, Photocatalysis, Hydrogen peroxide photolysis, Synergy
National Category
Biomaterials Science Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
URN: urn:nbn:se:uu:diva-211548DOI: 10.1016/j.apsusc.2013.08.057ISI: 000326579400032OAI: oai:DiVA.org:uu-211548DiVA: diva2:667501
Funder
Swedish Foundation for Strategic Research
Available from: 2013-11-26 Created: 2013-11-26 Last updated: 2017-12-06Bibliographically 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1250
Keyword
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
Identifiers
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)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research
Available from: 2015-05-12 Created: 2015-04-12 Last updated: 2015-07-07

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Publisher's full texthttp://dx.doi.org/10.1016/j.apsusc.2013.08.057

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