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Comparative characterization of oligomeric precursors intended for injectable implants
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry. (Polymer Chemistry)
2013 (English)In: Polymers for Advanced Technologies, ISSN 1042-7147, E-ISSN 1099-1581, Vol. 24, no 1, 15-21 p.Article in journal (Refereed) Published
Abstract [en]

The use of injectable materials is a simple approach for drug delivery and tissue repair, in, e.g. minimally invasive surgery applications. If these materials are used past their glass transition temperature and have a low viscosity, they will be able to flow while delivered in situ. Whether these materials are to be used as low viscosity drug carriers or further crosslinked for tissue repair, there is a need for a better understanding of their handling properties. In this study, oligo(trimethylene carbonate) (oTMC) and oligo[D,L-lactide-co-(«-caprolactone)] (oDLLA-co-CL) of various molecular weights within a relevant injectability range were synthesized via ring-opening polymerization. The materials were comparatively characterized by 1H NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography, and rheological measurements. After comparing the viscosities and molecular weights of the materials, it was concluded that oDLLA-co-CLs were, gener- ally, better suited as an injectable in situ crosslinking network, whereas oTMCs were found to be better candidates as injectable drug carriers. This study provides useful data and guidelines on the use of these and other similar oligomers intended for injectable implants.

Place, publisher, year, edition, pages
John Wiley & Sons, 2013. Vol. 24, no 1, 15-21 p.
Keyword [en]
oligomer(s), polyester(s), polycarbonate(s), rheology, injectable implant(s)
National Category
Medical Materials Polymer Chemistry
Research subject
Engineering Science with specialization in Materials Science; Chemistry with specialization in Polymer Chemistry
URN: urn:nbn:se:uu:diva-174546DOI: 10.1002/pat.3042ISI: 000312887500005OAI: oai:DiVA.org:uu-174546DiVA: diva2:527684
Available from: 2012-05-25 Created: 2012-05-22 Last updated: 2014-02-10Bibliographically approved
In thesis
1. Injectable Biomaterials for Spinal Applications
Open this publication in new window or tab >>Injectable Biomaterials for Spinal Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of injectable biomaterials is growing as the demands for minimally invasive procedures, and more easily applicable implants become higher, but their availability is still limited due to the difficulties associated to their design.

Each year, more than 700,000 vertebral compression fractures (VCF’s) are reported in the US and 500,000 VCF’s in Europe due to primary osteoporosis only. VCF’s can compromise the delicacy of the spinal canal and also cause back pain, which affects the patient’s quality of life. Vertebroplasty was developed in the 80’s, and has proven to be a safe minimally invasive procedure that can, quickly and sustainably, relieve the pain in patients experiencing VCF’s. However, biomaterials for vertebroplasty still have limitations. For instance, ceramic bone cements are difficult to distinguish from the bone using X-ray techniques. On the other hand, acrylic bone cements may cause adjacent vertebral fractures (AVF’s). Large clinical studies have indicated that 12 to 20% vertebroplasty recipients developed subsequent vertebral fractures, and that 41 to 67% of these, were AVF’s. This may be attributed to the load shifting and increased pressure on the adjacent endplates reached after vertebroplasty with stiff cements.

The primary aim of this thesis was to develop better injectable biomaterials for spinal applications, particularly, bone cements for vertebroplasty. Water-soluble radiopacifiers were first investigated to enhance the radiopacity of resorbable ceramic cements. Additionally, different strategies to produce materials that mechanically comply with the surrounding tissues (low-modulus bone cements) were investigated. When a suitable low-modulus cement was produced, its performance was evaluated in both bovine bone, and human vertebra ex vivo models.

In summary, strontium halides showed potential as water-soluble radiocontrast agents and could be used in resorbable calcium phosphates and other types of resorbable biomaterials. Conversely, linoleic acid-modified (low-modulus) cements appeared to be a promising alternative to currently available high-modulus cements. It was also shown that the influence of the cement properties on the strength and stiffness of a single vertebra depend upon the initial bone volume fraction, and that at low bone volume fractions, the initial mechanical properties of the vertebroplasty cement become more relevant. Finally, it was shown that vertebroplasty with low-modulus cements is biomechanically safe, and could become a recommended minimally invasive therapy in selected cases, especially for patients suffering from vertebral compression fractures due to osteoporosis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 66 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1114
injectable, biomaterials, bone cement, vertebral compression fractures, spine, radiopacity, minimally invasive treatment, low-modulus cement, oligomer, PMMA, calcium phosphate, vertebroplasty, bone
National Category
Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
urn:nbn:se:uu:diva-215606 (URN)978-91-554-8854-3 (ISBN)
Public defence
2014-02-28, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Available from: 2014-02-05 Created: 2014-01-15 Last updated: 2014-02-10

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