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Surfactant as a Critical Factor When Tuning the Hydrophilicity in Three-Dimensional Polyester-Based Scaffolds: Impact of Hydrophilicity on Their Mechanical Properties and the Cellular Response of Human Osteoblast-Like Cells
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
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2014 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 4, 1259-1268 p.Article in journal (Refereed) Published
Abstract [en]

In tissue engineering, the hydrophilicity of porous scaffolds is essential and influences protein and cell adhesion as well as nutrient diffusion into the scaffold. The relative low hydrophilicity of degradable polyesters, which limits diffusion of nutrients, is a major drawback in large porous scaffolds of these materials when used for bone tissue engineering and repair of critical size defects. Designing porous biodegradable polymer scaffolds with improved hydrophilicity, while maintaining their mechanical, thermal, and degradation properties is therefore of clinical interest. Here, surfactants were used to tune the hydrophilicity and material properties. A total of 3-20% (w/w) of surfactant, polysorbate 80 (Tween 80), was used as an additive in poly(L-lactide-co-1,5-diozepan-2-one) [poly(LLA-co-DXO)] and poly(L-lactide)-co-(epsilon-caprolactone) [poly(LLA-co-CL)] scaffolds. A significantly decreased water contact angle was recorded for all the blends and the crystallinity, glass transition temperature and crystallization temperature were reduced with increased amounts of surfactant. Copolymers with the addition of 3% Tween 80 had comparable mechanical properties as the pristine copolymers. However, the E-modulus and tensile stress of copolymers decreased significantly with the addition of 10 and 20% Tween 80. Initial cell response of the material was evaluated by seeding human osteoblast-like cells (HOB) on the scaffolds. The addition of 3% Tween 80 did not significantly influence cell attachment or proliferation, while 20% Tween 80 significantly inhibited osteoblast proliferation. RT-PCR results showed that 3% Tween 80 stimulated mRNA expression of alkaline phosphatase (ALP), osteoprotegerin (OPG), and bone morphogenetic protein-2 (BMP-2).

Place, publisher, year, edition, pages
2014. Vol. 15, no 4, 1259-1268 p.
Keyword [en]
Marrow Stromal Cells, Human-Endothelial Cells, Critical-Size Defects, In-Vitro, Bone, Differentiation, Wettability, Proteins, Adhesion, Proliferation
National Category
Biochemistry and Molecular Biology Polymer Technologies
URN: urn:nbn:se:kth:diva-145591DOI: 10.1021/bm401818eISI: 000334571600018ScopusID: 2-s2.0-84898669991OAI: diva2:723626
EU, FP7, Seventh Framework Programme, 242175

QC 20140611

Available from: 2014-06-11 Created: 2014-05-23 Last updated: 2014-09-29Bibliographically approved
In thesis
1. Engineering and Functionalization of Degradable Scaffolds for Medical Implant Applications
Open this publication in new window or tab >>Engineering and Functionalization of Degradable Scaffolds for Medical Implant Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The treatment of bone defects is facing the situation of lacking donations for autotransplantation. As a valid approach, scaffold-based tissue engineering combines the construction of well-defined porous scaffolds with advanced cell culturing technology to guide tissue regeneration. The role for the scaffold is to provide a suitable environment with a sufficient mechanical stiffness, supports for cell attachment, migration, nutrients and metabolite transport and space for cell remodeling and tissue regeneration. The random copolymers poly(L-lactide-co-ɛ-caprolactone) (poly(LLA-co-CL)) and poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) have been successfully incorporated into 3D porous scaffolds to induce specific interactions with cells and direct osteogenic cell differentiation. In this thesis, these scaffolds have been modified in chemical and physical ways to map and understand requirements for bone regeneration. Scaffold functionalities and properties, such as hydrophilicity, stiffness, size/shape, and reproducibility, were studied. The hydrophilicity was varied by adding 3–20 % (w/w) Tween 80 to poly(LLA-co-CL) and poly(LLA-co-DXO) respectively, which resulted in contact angles from 35° to 15°. With 3 % Tween 80, the resultant mechanical and thermal properties were similar to pristine polymer materials. Tween 80 did not significantly influence cell attachment or proliferation but did stimulate the mRNA expression of osteogenetic markers. The surface functionality and mechanical properties were altered by introducing nanodiamond particles (n-DP) into poly(LLA-co-CL) scaffolds by means of surface physisorption or hybrid blending. Scaffold with n-DP physisorbed showed improved cell attachment, differentiation, and bone reformation. Hybrid n-DP/poly(LLA-co-CL) composites were obtained by direct blending of polylactide modified n-DP (n-DP-PLA) with poly(LLA-coCL). The n-DP-PLA was prepared by sodium hydride-mediated anionic polymerization using n-DP as the initiator. Prepared n-DP-PLA could be dispersed homogenously in organic solvents and blended with poly(LLA-coCL) solution. The n-DP-PLA particles were homogenously distributed in the composite material, which significantly improved mechanical properties. For comparison, the addition of benzoquinone-modified n-DP (n-DP-BQ) did not reinforce poly(LLA-co-CL). This indicated the importance of specific surface grafting, which determined different particle-polymer interactions. For the treatment of critical size defects, a large porous poly(LLA-co-CL) scaffold (12.5 mm diameter × 25 mm thickness) was developed and produced by molding and salt-leaching methods. The large porous scaffolds were evaluated in a scaffold-customized perfusion-based bioreactor system. It was obvious that the scaffold could support improved cell distribution and support the stimulation of human mesenchymal stem cell (hMSC) especially with dynamic flow in a bioreactor. To improve the scaffolding technique, a three-dimensional fiber deposition (3DF) technique was employed to build layer-based scaffolds. Poly(LLA-coCL) scaffolds produced by the 3DF method showed enhanced mechanical properties and a homogeneous distribution of human osteoblasts (hOBs) in the scaffolds. Although poly(LLA-co-CL) was thermally degraded, the degradation did not influence the scaffold mechanical properties. Based on the computerized design, a 3DF scaffold of amorphous copolymer poly(LLAco-CL) provides high-precision control and reproducibility. In summary, the design of porous scaffolds is one of the essential factors in tissue engineering as to mimicking the intrinsic extracellular environment. For bone tissue engineering, an optimized scaffold can maintain a contact angle greater than 35 degrees. Pristine or modified n-DP, introduced as an additive by surface physisorption or direct blending, can improve scaffold mechanical properties and cell response. Various sizes of scaffolds can be easily produced by a mold-mediated salt-leaching method. However, when 100 % reproducibility is required, the 3DF method can be used to create customizable scaffolds.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 73 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:36
Tissue engineering, nanodiamond, scaffold, bioreactor
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
urn:nbn:se:kth:diva-152605 (URN)978-91-7595-256-7 (ISBN)
Public defence
2014-10-17, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:44 (English)
EU, FP7, Seventh Framework Programme, Vascubone

QC 20140929

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2014-09-29Bibliographically approved

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