Control of pore structure and size in freeze‐dried collagen sponges

Schoof, H.; Apel, Jörn; Heschel, I.; Rau, G.

doi:10.1002/jbm.1028

Cited by 380 publications

(218 citation statements)

References 23 publications

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“…Each fabrication method produces a different set of mechanical and biochemical properties. Methods that induce pore formation such as freeze-drying process result in greater porosity which allows greater cellular and soluble factor infiltration into the materials whilst decreases the inherent biomechanical strength of the material [75]. Collagen hydrogels are easy to make and forms a gel that can absorb large amounts of fluid which aids in cellular infiltration.…”

Section: Natural Materialsmentioning

confidence: 99%

Bioengineering of Articular Cartilage: Past, Present and Future

Felimban

Moulton

et al. 2013

Regen. Med.

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The treatment of cartilage defects poses a clinical challenge owing to the lack of intrinsic regenerative capacity of cartilage. The use of tissue engineering techniques to bioengineer articular cartilage is promising and may hold the key to the successful regeneration of cartilage tissue. Natural and synthetic biomaterials have been used to recreate the microarchitecture of articular cartilage through multilayered biomimetic scaffolds. Acellular scaffolds preserve the microarchitecture of articular cartilage through a process of decellularization of biological tissue. Although promising, this technique often results in poor biomechanical strength of the graft. However, biomechanical strength could be improved if biomaterials could be incorporated back into the decellularized tissue to overcome this limitation.

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Section: Natural Materialsmentioning

confidence: 99%

Bioengineering of Articular Cartilage: Past, Present and Future

Felimban

Moulton

et al. 2013

Regen. Med.

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“…Fig. 8 displays the ESEM image of the graded composite: it is possible to distinguish a disordered lower layer that corresponds to the mineralized one, a second layer, with lower mineralization extent, which corresponds to the tidemark and a third layer in which the propagation of a planar ice front [33] during a freeze-dry cycle, causes the formation of a columnar-like structure converging towards the external surface where it forms horizontal flat ribbons, resembling the morphology of the lamina splendens. In the lower layer, the higher density and scarce flexibility of the mineralized fibers hamper the formation of a directionally ordered structure during freeze-drying.…”

Section: Development and Test Of The Three-layered Scaffoldmentioning

confidence: 99%

Design of graded biomimetic osteochondral composite scaffolds

et al. 2008

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With the ultimate goal to generate suitable materials for the repair of osteochondral defects, in this work we aimed at developing composite osteochondral scaffolds organized in different integrated layers, with features which are biomimetic for articular cartilage and subchondral bone and can differentially support formation of such tissues.A biologically inspired mineralization process was first developed to nucleate Mg-doped hydroxyapatite crystals on type I collagen fibers during their self assembling. The resulting mineral phase was non-stoichiometric and amorphous, resembling chemico-physical features of newly deposited, natural bone matrix. A graded material was then generated, consisting of (i) a lower layer of the developed biomineralized collagen, corresponding to the subchondral bone, (ii) an upper layer of hyaluronic acid-charged collagen, mimicking the cartilaginous region, and (iii) an intermediate layer of the same nature as the biomineralized collagen, but with a lower extent of mineral, resembling the tidemark. The layers were stacked and freeze-dried, to obtain an integrated, monolithic composite. Culture of the material for 2 weeks after loading with articular chondrocytes yielded cartilaginous tissue formation selectively in the upper layer. Conversely, ectopic implantation in nude mice of the material after loading with bone marrow stromal cells resulted in bone formation which remained confined within the lower layer.In conclusion, we developed a composite material with cues which are biomimetic of an osteochondral tissue and with the capacity to differentially support cartilage and bone tissue generation. The results warrant test of the material as a substitute for the repair of osteochondral lesions in orthotopic animal models. Response to Reviewer #1:1) results and discussion should be separated We would prefer to maintain Results and Discussion combined, in order to avoid possible redundancies and improve readability. 2) figures should be detailed with arrows and information about specific orientations. Details and arrows have been included in the Figures3) collagen type 1 was used for the creation of the construct -in every layer? Usually collagen type 1 does not play a role in articular cartilage. This should be addressed in the discussion. According to the Reviewer's comment, a rationale for the use of type I collagen has been included in the text, as follows: "Type I collagen was selected for the synthesis of the composite layers, including the cartilaginous one, due to (i) its good physico-chemical stability and processability and (ii) high safety and biocompatibility profile, related to the removal of all Reply Letter to Editor and referee's comments telopeptides, which are potentially responsible for immunological reactions." (Section 2.1, Page 2, 1 st paragraph). Indeed, type II collagen is normally extracted porcine derivative, and is still not available either in bulk for processing or for clinical use. Nowadays there are only few papers on experimental studies desc...

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“…12,13 As the pore structure of the scaffold mirrors the ice crystal structure formed during freezing, pore structure can be effectively controlled by altering the freezing process used during freeze-drying. 14 Accordingly, modifications to this process are the key to creating a range of scaffolds with different pore structures.…”

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confidence: 99%

Novel Freeze-Drying Methods to Produce a Range of Collagen–Glycosaminoglycan Scaffolds with Tailored Mean Pore Sizes

Haugh

Murphy

O’Brien

2010

Tissue Engineering Part C: Methods

223

196

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• to copy, distribute, display, and perform the work.• to make derivative works. Under the following conditions:• Attribution -You must give the original author credit.• Non-Commercial -You may not use this work for commercial purposes.• The pore structure of three-dimensional scaffolds used in tissue engineering has been shown to significantly influence cellular activity. As the optimal pore size is dependant on the specifics of the tissue engineering application, the ability to alter the pore size over a wide range is essential for a particular scaffold to be suitable for multiple applications. With this in mind, the aim of this study was to develop methodologies to produce a range of collagen-glycosaminoglycan (CG) scaffolds with tailored mean pore sizes. The pore size of CG scaffolds is established during the freeze-drying fabrication process. In this study, freezing temperature was varied (À108C to À708C) and an annealing step was introduced to the process to determine their effects on pore size. Annealing is an additional step in the freeze-drying cycle that involves raising the temperature of the frozen suspension to increase the rate of ice crystal growth. The results show that the pore size of the scaffolds decreased as the freezing temperature was reduced. Additionally, the introduction of an annealing step during freeze-drying was found to result in a significant increase (40%) in pore size. Taken together, these results demonstrate that the methodologies developed in this study can be used to produce a range of CG scaffolds with mean pore sizes from 85 to 325 mm. This is a substantial improvement on the range of pore sizes that were possible to produce previously (96-150 mm). The methods developed in this study provide a basis for the investigation of the effects of pore size on both in vitro and in vivo performance and for the determination of the optimal pore structure for specific tissue engineering applications.

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Control of pore structure and size in freeze‐dried collagen sponges

Cited by 380 publications

References 23 publications

Bioengineering of Articular Cartilage: Past, Present and Future

Bioengineering of Articular Cartilage: Past, Present and Future

Design of graded biomimetic osteochondral composite scaffolds

Novel Freeze-Drying Methods to Produce a Range of Collagen–Glycosaminoglycan Scaffolds with Tailored Mean Pore Sizes

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