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Bioactive Coatings and Antibacterial Approaches for Titanium Medical Implants
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to characterize and manufacture coatings and surfaces with antibacterial properties and retained or enhanced bioactivity and biocompatibility. The aim was also to study the optimal composition and parameters of mixtures for debridement of bacterial biofilms on titanium surfaces. The mixtures contained TiO2 particles and H2O2 and were irradiated by light to activate reactive oxygen species (ROS) formation.

In the first part of the thesis, characterization of a thin, multifunctional hydroxyapatite (HA) coating was performed. The coating was applied to anodized cancellous bone screws with the purpose of stimulating local bone formation without bonding too firmly and providing local antibacterial effect. Specifications of the coating included a thickness of around 1 µm, high crystallinity, Ca/P ratio close to the theoretical value of 1.67 and comprise the functional groups of HA. Additionally, the adhesion of the coating to the substrate should be stronger than the cohesion of the coating. Characterization results showed that the coating met the specification for all criteria.        

In the second part of the thesis, titanium discs were soaked in H2O2 and subsequently in NaOH and Ca(OH)2 to acquire an antibacterial surface that at the same time is bioactive and biocompatible. The surface demonstrated bioactive properties, assessed by soaking in phosphate buffered saline for seven days in 37°C and examined in scanning electron microscopy and X-ray diffraction.

The third part of the thesis consisted of studying the ROS generation of TiO2/H2O2 mixtures irradiated with UV-Vis light, and to study the antibacterial effect of these mixtures on S. epidermidis Xen 43 and Pseudomonas aeruginosa biofilms on titanium surfaces. The generation of ROS from different TiO2 crystalline forms and different H2O2 concentrations under light UV-Vis irradiation was determined by rhodamine B degradation. It showed that rutile and 1-3.5 mM H2O2 resulted in the highest degradation of all combinations with almost 100% degradation under 365 nm light and 77% degradation under 405 nm light after 10 min.

The debridement of the S. epidermidis and P. aeruginosa biofilm discs showed that 0.95 M (3%) H2O2 was the most effective parameter for disinfection of the discs. The addition of TiO2 particles showed a significant extra effect in one of the three studies.

Place, publisher, year, edition, pages
Uppsala: Uppsala University, 2018. , p. 63
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1712
Keywords [en]
Bioactivity, antibacterial, titanium, hydrogen peroxide, hydroxyapatite, biomaterial
National Category
Other Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-358253ISBN: 978-91-513-0424-3 (print)OAI: oai:DiVA.org:uu-358253DiVA, id: diva2:1241945
Public defence
2018-10-12, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-09-20 Created: 2018-08-27 Last updated: 2018-10-15
List of papers
1. Development of a novel multifunctional hydroxyapatite coating for orthopedic implants
Open this publication in new window or tab >>Development of a novel multifunctional hydroxyapatite coating for orthopedic implants
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(English)Manuscript (preprint) (Other academic)
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-358028 (URN)
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-08-27
2. Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility
Open this publication in new window or tab >>Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility
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2019 (English)In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 96, p. 272-279Article in journal (Refereed) Published
Abstract [en]

Bacterial infections associated with metal implants are severe problems affecting a considerable amount of people with dental or orthopedic implants. This study aims to examine the antibacterial effect of a Titanium-peroxy gel layer on the modified surface of commercially pure titanium grade 2. Variations in a multi-step surface modification procedure were tested to determine the best combination that provided an antibacterial effect while enhancing bioactivity without compromising biocompatibility. Soaking the surfaces in 30 wt% hydrogen peroxide held at 80 °C provided antibacterial activity while subsequent surface treatments in concentrated sodium and calcium hydroxide solutions were preformed to enhance bioactivity. Staphylococcus epidermidis was used to determine the antibacterial effect through both direct contact and biofilm inhibition tests while human dermal fibroblast cells and MC3T3 pre osteoblast cells were utilized to test biocompatibility. The greatest antibacterial effect was observed with only hydrogen peroxide treatment, but the resulting surface was neither bioactive nor biocompatible. It was found that subsequent surface treatments with sodium hydroxide followed by calcium hydroxide provided a bioactive surface that was also biocompatible. Additionally, a final treatment with autoclaving showed positive effects with regards to enhanced bioactivity. This multi-step surface modification procedure offers a promising, non-antibiotic, solution for combatting infections associated with biomedical implants.

Keywords
Titanium, Antibacterial, Bioactivity, Cell viability, Sodium titanate, Calcium titanate
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-358023 (URN)10.1016/j.msec.2018.11.021 (DOI)000456760700027 ()30606532 (PubMedID)
Funder
Vinnova
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-03-15Bibliographically approved
3. Thromboinflammation as bioactivity assessment of H2O2-alkali modified titanium surfaces
Open this publication in new window or tab >>Thromboinflammation as bioactivity assessment of H2O2-alkali modified titanium surfaces
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2019 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 30, no 6, article id 66Article in journal (Refereed) Published
Abstract [en]

The release of growth factors from platelets, mediated by the coagulation and the complement system, plays an important role in the bone formation around implants. This study aimed at exploring the thromboinflammatory response of H2O2-alkali soaked commercially pure titanium grade 2 discs exposed to whole human blood, as a way to assess the bioactivity of the discs. Commercially pure titanium grade 2 discs were modified by soaking in H2O2, NaOH and Ca(OH)2. The platelet aggregation, coagulation activation and complement activation was assessed by exposing the discs to fresh whole blood from human donors. The platelet aggregation was examined by a cell counter and the coagulation and complement activation were assessed by ELISA-measurements of the concentration of thrombin-antithrombin complex, C3a and terminal complement complex. The modified surface showed a statistically significant increased platelet aggregation, coagulation activation and complement activation compared to unexposed blood. The surface also showed a statistically significant increase of coagulation activation compared to PVC. The results of this study showed that the H2O2-alkali soaked surfaces induced a thromboinflammatory response that indicates that the surfaces are bioactive.

National Category
Other Materials Engineering Biomaterials Science
Identifiers
urn:nbn:se:uu:diva-358034 (URN)10.1007/s10856-019-6248-4 (DOI)000468976700001 ()31127371 (PubMedID)
Funder
Swedish Research Council, 2016-2075-5.1; 2016-04519Vinnova
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-06-25Bibliographically approved
4. Organic degradation potential of a TiO2/H2O2/UV-Vis system for dental applications
Open this publication in new window or tab >>Organic degradation potential of a TiO2/H2O2/UV-Vis system for dental applications
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2017 (English)In: Journal of Dentistry, ISSN 0300-5712, E-ISSN 1879-176X, Vol. 67, p. 53-57Article in journal (Refereed) Published
Abstract [en]

Objectives

The combination of TiO2 and H2O2 under light activation constitutes a promising method for disinfection of dental prosthetics and implants, due to production of reactive oxygen species (ROS). The aim of this work was to investigate the organic degradation ability of TiO2 particles in combination with H2O2 and under light activation utilizing the organic dye rhodamine B (RhB).

Methods

Five different types of TiO2 particles, consisting of anatase, rutile, or a mixture of these crystalline phases, were combined with H2O2 and RhB, and subsequently exposed to UV (365 nm) or visible (405 nm) light at an irradiance of 2.1 mW/cm2.

Results

It was found that rutile in combination with low concentrations of H2O2 (1.0–3.5 mM) resulted in a degradation of RhB of 96% and 77% after 10 min exposure to 365 nm and 405 nm light, respectively, which was the highest degradation of all test groups. Control measurements performed without light irradiation or irradiation at 470 nm, or without TiO2 particles resulted in little or no degradation of RhB.

Conclusions

Low H2O2 concentrations (1.0 mM–3.5 mM) and visible light (405 nm) used in combination with rutile TiO2 particles showed the highest RhB degradation capacity.

Clinical significance

A combination of TiO2 particles and H2O2 exposed to low energy UV or high energy visible light has an organic degradation capability that could be utilized in applications to kill or inactivate bacteria on medical devices such as dental implants for treatment against, e.g., peri-implantitis.

Keywords
TiO, HO, Reactive oxygen species, Rhodamine B, Rutile
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-330202 (URN)10.1016/j.jdent.2017.09.001 (DOI)000417204800007 ()28886983 (PubMedID)
Funder
VINNOVA, E!8320
Available from: 2017-09-27 Created: 2017-09-27 Last updated: 2018-08-27Bibliographically approved
5. Debridement of Bacterial Biofilms with TiO2/H2O2 Solutions and Visible Light Irradiation
Open this publication in new window or tab >>Debridement of Bacterial Biofilms with TiO2/H2O2 Solutions and Visible Light Irradiation
2018 (English)In: International Journal of Biomaterials, ISSN 1687-8787, E-ISSN 1687-8795, Vol. 2018, article id 5361632Article in journal (Refereed) Published
Abstract [en]

Objectives. The aim of the study was to explore the debridement efficacy of different solutions of H2O2 and rutile particles against Staphylococcus epidermidis and Pseudomonas aeruginosa biofilms attached to titanium surfaces when exposed to visible light. Materials and Methods. Titanium discs cultivated with biofilms of Staphylococcus epidermidis or Pseudomonas aeruginosa were subjected for 1 min to suspensions consisting of rutile particles mixed with high (950 mM) or low (2 mM) concentrations of H2O2 under visible light irradiation (405 nm; 2.1 mW/cm2). Discs were rinsed and the degree of debridement was determined through scanning electron microscopy and viability assessment of the remaining bacteria using luminescence measurements and/or a metabolic activity assay. Results. Cleaning mixtures containing the higher concentration of H2O2 showed a significantly improved debridement compared to the negative control in all experiments. The addition of rutile particles was shown to have a statistically significant effect in one test with S. epidermidis. Limited evidence of the catalytic effect of visible light irradiation was seen, but effects were relatively small and statistically insignificant. Conclusions. H2O2 at a concentration of 950 mM proved to be the strongest contribution to the debridement and bactericidal effect of the cleaning techniques tested in this study.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2018
National Category
Nano Technology Biomaterials Science
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials; Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-355674 (URN)10.1155/2018/5361632 (DOI)000438846900001 ()30057613 (PubMedID)
Funder
VINNOVA, E!8320
Available from: 2018-07-03 Created: 2018-07-03 Last updated: 2018-09-26Bibliographically approved

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