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Sol-gel derived titania coating with immobilized bisphosphonate enhances screw fixation in rat tibia
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
University of Turku.
Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Orthopaedic Centre, Department of Orthopaedics Linköping.
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
2010 (English)In: JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, ISSN 1549-3296, Vol. 94A, no 2, 389-395 p.Article in journal (Refereed) Published
Abstract [en]

A variety of surface modifications have been tested for the enhancement of screw fixation in bone, and locally delivered anti-osteoporosis drugs such as bisphosphonates (BP) are then of interest. In this in vivo study, the impact of surface immobilized BP was compared with systemic BP delivery and screws with no BP. After due in vitro characterization, differently treated stainless steel (SS) screws were divided into four groups with 10 rats each. Three of the groups received screws coated with sol gel derived TiO2 and calcium phosphate (SS+TiO2+CaP). One of these had no further treatment, one had alendronate (BP) adsorbed to calcium phosphate mineral, and one received systemic BP treatment. The fourth group received uncoated SS screws and no BP (control). The screw pullout force was measured after 4 weeks of implantation in rat tibiae. The immobilized amount and release rate of alendronate could be controlled by different immersion times. The SS+TiO2+CaP coating did not increase the pullout force compared to SS alone. Surface delivered alendronate enhanced the pullout force by 93% [p = 0.000; 95% Confidence Interval (CI): 67-118%] compared to SS, and by 39% (p = 0.044; 95% CI: 7-71%) compared to systemic alendronate delivery. Both surface immobilized and systemically delivered alendronate improved implant fixation. Also, locally delivered, that is, surface immobilized alendronate showed a better fixation than systemically delivered. Using sot gel derived TiO2 as a platform, it is possible to administer controllable amounts of a variety of BPs.

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd , 2010. Vol. 94A, no 2, 389-395 p.
Keyword [en]
screw; bone; bisphosphonates; sol-gel; rat
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-58262DOI: 10.1002/jbm.a.32708ISI: 000279482600006OAI: diva2:337958
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2011-10-10
In thesis
1. Improved titanium and steel implants: Studies on bisphosphonate, strontium and surface treatments
Open this publication in new window or tab >>Improved titanium and steel implants: Studies on bisphosphonate, strontium and surface treatments
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Purpose: The general aim of this thesis was to increase the understanding of biomaterial surface modifications and local delivery of osteoporosis drugs for bone integration. We therefore (i) characterised and investigated model surface coatings for controlled drug delivery in a rat tibia screw model (ii) elucidated the effect of surface treatment for activation of complement system in vitro.

Materials and methods: Bisphosphonate was immobilised directly to implant surfaces by two methods. In the first method, bisphosphonate was bound via a crosslinked fibrinogen layer to titanium surfaces. In the second method, stainless steel screws were first dip coated in a TiO2 solgel, and thereafter incubated in simulated body fluid (SBF). The so prepared thin calcium phosphate layer on titania bound then bisphosphonate directly with high affinity. The drug release kinetics was determined in vitro by 14C marked alendronate that was quantified with scintillation techniques. The screws were inserted in the metaphysis of rat tibia and the mechanical fixation monitored by screw pullout measurements after 2 or 4 weeks of implantation. In order to compare two different osteoporosis drugs, bisphosphonate and strontium ranelate, stainless steel and PMMA screws were inserted in the tibial metaphysis of rat for 4 and 8 weeks. Bisphosphonate was then delivered subcutaneously and strontium ranelate orally during the whole implantation period. The mechanical fixation was analysed by pullout force measurements, and bone architecture studied by micro-computed tomography (μCT). The immune complement activation on sol-gel- and smooth titanium surfaces was analysed in human blood plasma before and after annealing of titanium at 100-500ºC or upon UVO-treatment for up to 96 hours.

Results: Bisphosphonate coated screws enhanced the screw pull out force after 2 weeks of implantation by more than 30% (fibrinogen coating) and by 93% after 4 weeks (sol-gel derived TiO2 coating). Systemically administered bisphosphonate enhanced the mechanical screw fixation after 4 weeks by more than 96% and after 8 weeks by more than 55% as compared to strontium ranelate treated animals (p = 0.00). Strontium ranelate treatment did not show significant improvement of screw pullout force after 4 and 8 weeks, compared to control. The immune complement surface deposition from blood plasma vanished irreversibly after Ti heat treatment at 250-300 ºC during 30 minutes or after UVO exposure for 24 hours or longer. Tentatively, changes in surface water/hydroxyl binding upon heat- and UVO treatments were observed by XPS and infrared spectroscopy.

Conclusions: The results show that fixation at short implantation time (weeks) of orthopaedic implant can be enhanced by immobilised bisphosphonate on stainless steel or titanium implants. Systemic delivery of strontium ranelate showed no significant effect on implant fixation in rat tibia, and we hypothesise therefore that strontium ranelate will not become a power tool to increase the early implant fixation, but may be beneficial at longer times. Heat annealing or UVO-treatment of titanium surfaces change the surface hydroxylation, leading to decreased immune complement deposition from blood plasma.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 75 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1391
National Category
Natural Sciences
urn:nbn:se:liu:diva-71289 (URN)978-91-7393-085-7 (ISBN)
Public defence
2011-10-07, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Available from: 2011-10-10 Created: 2011-10-10 Last updated: 2011-10-10Bibliographically approved

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Linderbäck, PaulaAspenberg, PerTengvall, Pentti
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Department of Physics, Chemistry and BiologyThe Institute of TechnologyOrthopaedics and Sports MedicineFaculty of Health SciencesDepartment of Orthopaedics LinköpingApplied Physics
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