TUTCRIS - Tampereen teknillinen yliopisto


Highly Porous Freeze-Dried Composite Scaffolds for Cartilage and Osteochondral Tissue Engineering



KustantajaTampere University of Technology
ISBN (elektroninen)978-952-15-3491-1
ISBN (painettu)978-952-15-3484-3
TilaJulkaistu - 17 huhtikuuta 2015
OKM-julkaisutyyppiG5 Artikkeliväitöskirja


NimiTampere University of Technology. Publication
KustantajaTampere University of Technology
ISSN (painettu)1459-2045


Cartilage lesions are known to heal poorly and their tissue engineering with optimal scaffolds are widely studied. If the cartilage lesion is deep, there is a need to also repair the underlying bone (i.e. subchondral bone) and the lesion is called an osteochondral lesion. There are several methods used for osteochondral tissue engineering and various scaffold compositions are being studied. The studied scaffold compositions include the one scaffold method, where only one scaffold is used for the osteochondral lesion, or independent structures for cartilage and bone. These two scaffolds could be combined during processing, before surgery or in surgery to obtain osteochondral solutions for cartilage repair. In this thesis, freeze-drying was used to manufacture highly porous scaffolds with an interconnected pore structure. Natural polymer-based scaffolds often lack the required mechanical stability. Therefore, natural polymer-based hybrids with improved stiffness were manufactured for cartilage tissue engineering scaffolds. Synthetic polymer-based composites with improved osteoconductivity were manufactured for bone or osteochondral tissue engineering scaffolds. The scaffolds were studied to determine the structure of the scaffolds, the effect of the fibrous filler mesh or filler particles on the characteristics of the hybrids or composites, and the suitability of the hybrids for cartilage tissue engineering and the composites for bone or osteochondral tissue engineering. The majority of the studied scaffolds were also cultured with cells in vitro to define the suitability of the scaffolds for tissue engineering. The results show the freeze-drying method to be useful for manufacturing highly porous hybrid and composite scaffolds with improved properties compared with plain polymer scaffolds. Also, all the studied scaffolds had an interconnected porous structure. Improved wettability characteristics showed the method of cross-linking collagen post freeze-drying to be more effective way of cross-linking collagen compared to crosslinking collagen prior to freeze-drying. Synthetic polymer-based composites with an inhomogeneous scaffold structure with β-tricalcium phosphate (TCP) or bioactive glass (BG) filler particles showed improved osteoconductivity. TCP was found to improve the cell proliferation and alkaline phosphatase (ALP) activity of adipose stem cells (ASCs) over plain poly(L/D,L)lactide 70/30 (PLA70) scaffolds or PLA70+BG composites. A porous polymer matrix with a highly porous fibrous filler was successfully combined into highly porous freeze-dried hybrids with a natural polymer matrix (collagen/ chitosan and poly(L/D)lactide 96/4 fibres (PLA96)) and composites with a synthetic polymer matrix (poly(D,L-lactide-co-glycolide)70/30 (PLGA)) with bioactive glass fibres (BGf). The PLA96 fibrous mesh improved the penetration of the chondrocytes into the hybrids compared with plain natural polymer scaffolds. The manufactured scaffolds were found to be applicable for cartilage, bone and osteochondral tissue engineering applications. Based on the structures developed in this thesis, more optimal scaffold structures are currently being studied.

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