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      Fabrication of Porous Scaffolds with a Controllable Microstructure and Mechanical Properties by Porogen Fusion Technique

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          Abstract

          Macroporous scaffolds with controllable pore structure and mechanical properties were fabricated by a porogen fusion technique. Biodegradable material poly ( d, l-lactide) (PDLLA) was used as the scaffold matrix. The effects of porogen size, PDLLA concentration and hydroxyapatite (HA) content on the scaffold morphology, porosity and mechanical properties were investigated. High porosity (90% and above) and highly interconnected structures were easily obtained and the pore size could be adjusted by varying the porogen size. With the increasing porogen size and PDLLA concentration, the porosity of scaffolds decreases, while its mechanical properties increase. The introduction of HA greatly increases the impact on pore structure, mechanical properties and water absorption ability of scaffolds, while it has comparatively little influence on its porosity under low HA contents. These results show that by adjusting processing parameters, scaffolds could afford a controllable pore size, exhibit suitable pore structure and high porosity, as well as good mechanical properties, and may serve as an excellent substrate for bone tissue engineering.

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          Most cited references34

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          Review: tissue engineering for regeneration of articular cartilage.

          Joint pain due to cartilage degeneration is a serious problem, affecting people of all ages. Although many techniques, often surgical, are currently employed to treat this affliction, none have had complete success. Recent advances in biology and materials science have pushed tissue engineering to the forefront of new cartilage repair techniques. This review seeks to condense information for the biomaterialist interested in developing materials for this application. Articular cartilage anatomy, types of injury, and current repair methods are explained. The need for biomaterials, current commonly used materials for tissue-engineered cartilage, and considerations in scale-up of cell-biomaterial constructs are summarized.
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            Novel approach to fabricate porous sponges of poly(D,L-lactic-co-glycolic acid) without the use of organic solvents.

            A novel method was developed to produce highly porous sponges for potential use in tissue engineering, without the use of organic solvents. Highly porous sponges of biodegradable polymers are frequently utilized in tissue engineering both to transplant cells or growth factors, and to serve as a template for tissue regeneration. The processes utilized to fabricate sponges typically use organic solvents, but organic residues remaining in the sponges may be harmful to adherent cells, protein growth factors or nearby tissues. This report describes a technique to fabricate macroporous sponges from synthetic biodegradable polymers using high pressure carbon dioxide processing at room temperature. Solid discs of poly (D,L-lactic-co-glycolic acid) were saturated with CO2 by exposure to high pressure CO2 gas (5.5 MPa) for 72 h at room temperature. The solubility of the gas in the polymer was then rapidly decreased by reducing the CO2 gas pressure to atmospheric levels. This created a thermodynamic instability for the CO2 dissolved in the polymer discs, and resulted in the nucleation and growth of gas cells within the polymer matrix. Polymer sponges with large pores (approximately 100 microns) and porosities of up to 93% could be fabricated with this technique. The porosity of the sponges could be controlled by the perform production technique, and mixing crystalline and amorphous polymers. Fibre-reinforced foams could also be produced by placing polymer fibres within the polymer matrix before CO2 gas processing.
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              Poly(lactide-co-glycolide)/hydroxyapatite composite scaffolds for bone tissue engineering.

              Biodegradable polymer/bioceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes such as brittleness and difficulty in shaping. However, conventional methods for fabricating polymer/bioceramic composite scaffolds often use organic solvents (e.g., the solvent casting and particulate leaching (SC/PL) method), which might be harmful to cells or tissues. Furthermore, the polymer solutions may coat the ceramics and hinder their exposure to the scaffold surface, which may decrease the likelihood that the seeded osteogenic cells will make contact with the bioactive ceramics. In this study, a novel method for fabricating a polymer/nano-bioceramic composite scaffold with high exposure of the bioceramics to the scaffold surface was developed for efficient bone tissue engineering. Poly(D,L-lactic-co-glycolic acid)/nano-hydroxyapatite (PLGA/HA) composite scaffolds were fabricated by the gas forming and particulate leaching (GF/PL) method without the use of organic solvents. The GF/PL method exposed HA nanoparticles at the scaffold surface significantly more than the conventional SC/PL method does. The GF/PL scaffolds showed interconnected porous structures without a skin layer and exhibited superior enhanced mechanical properties to those of scaffolds fabricated by the SC/PL method. Both types of scaffolds were seeded with rat calvarial osteoblasts and cultured in vitro or were subcutaneously implanted into athymic mice for eight weeks. The GF/PL scaffolds exhibited significantly higher cell growth, alkaline phosphatase activity, and mineralization compared to the SC/PL scaffolds in vitro. Histological analyses and calcium content quantification of the regenerated tissues five and eight weeks after implantation showed that bone formation was more extensive on the GF/PL scaffolds than on the SC/PL scaffolds. Compared to the SC/PL scaffolds, the enhanced bone formation on the GF/PL scaffolds may have resulted from the higher exposure of HA nanoparticles at the scaffold surface, which allowed for direct contact with the transplanted cells and stimulated the cell proliferation and osteogenic differentiation. These results show that the biodegradable polymer/bioceramic composite scaffolds fabricated by the novel GF/PL method enhance bone regeneration compared with those fabricated by the conventional SC/PL method.
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                Author and article information

                Journal
                Int J Mol Sci
                ijms
                International Journal of Molecular Sciences
                Molecular Diversity Preservation International (MDPI)
                1422-0067
                25 January 2011
                2011
                : 12
                : 2
                : 890-904
                Affiliations
                [1 ] Institute of Nano- and Bio-Polymeric Materials, School of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; E-Mails: renjie65@ 123456163.com (J.R.); yourchenchu@ 123456163.com (C.C.)
                [2 ] Key Laboratory Advanced Civil Engineering Materials, Ministry of Education, School of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
                [3 ] Department of General Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiaotong University, 1665 Kongjiang Road, Shanghai 200092, China; E-Mail: jxlisg@ 123456yahoo.cn
                Author notes
                [* ]Author to whom correspondence should be addressed; E-Mail: qgtan@ 123456tongji.edu.cn ; Tel.: +86-21-69580234; Fax: +86-21-69580234.
                Article
                ijms-12-00890
                10.3390/ijms12020890
                3083679
                21541032
                4c758496-35e2-47d6-8382-dbcb8e45bcda
                © 2011 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 2 November 2010
                : 4 January 2011
                : 24 January 2011
                Categories
                Article

                Molecular biology
                porogen fusion technique,composite scaffolds,mechanical property,tissue engineering

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