Biodegradable elastomeric materials have gained much recent attention in the field of soft tissue engineering. Poly(glycerol sebacate) (PGS) is one of a new family of elastomers which are promising candidates used for soft tissue engineering. However, PGS has a limited range of mechanical properties and has drawbacks, such as cytotoxicity caused by the acidic degradation products of very soft PGS and degradation kinetics that are too fast in vivo to provide sufficient mechanical support to the tissue. However, the development of PGS/based elastomeric composites containing alkaline bioactive fillers could be a method for addressing these drawbacks and thus may pave the way towards wide clinical applications. In this study, we synthesized a new PGS composite system consisting of a micron-sized Bioglass filler. In addition to much improved cytocompatibility, the PGS/Bioglass composites demonstrated three remarkable mechanical properties. First, contrary to previous reports, the addition of microsized Bioglass increases the elongation at break from 160 to 550%, while enhancing the Young's modulus of the composites by up to a factor of four. Second, the modulus of the PGS/Bioglass composites drops abruptly in a physiological environment (culture medium), and the level of drop can be tuned such that the addition of Bioglass does not harden the composite in vivo and thus the desired compliance required for soft tissue engineering are maintained. Third, after the abrupt drop in modulus, the composites exhibited mechanical stability over an extended period. This latter observation is an important feature of the new composites, because they can provide reliable mechanical support to damaged tissues during the lag phase of the healing process. These mechanical properties, together with improved biocompatibility, make this family of composites better candidates than plastic and related composite biomaterials for the applications of tissue engineering.
"To overcome these limitations, making a composite with bioceramics of PGS could be a potential strategy. For example, the investigation of PGS- Bioglass Ò composites developed by Liang et al. (2010) showed that the addition of Bioglass Ò filler to PGS could be a control of degradation kinetics, which is independent of the mechanical properties of the composites. In addition, the composites have significantly improved biocompatibility compared with pure PGS. "
[Show abstract][Hide abstract] ABSTRACT: Tissue engineering is essentially a technique for imitating nature. Natural tissues consist of three components: cells, signalling systems (e.g. growth factors) and extracellular matrix (ECM). The ECM forms a scaffold for its cells. Hence, the engineered tissue construct is an artificial scaffold populated with living cells and signalling molecules. A huge effort has been invested in bone tissue engineering, in which a highly porous scaffold plays a critical role in guiding bone and vascular tissue growth and regeneration in three dimensions. In the last two decades, numerous scaffolding techniques have been developed to fabricate highly interconnective, porous scaffolds for bone tissue engineering applications. This review provides an update on the progress of foaming technology of biomaterials, with a special attention being focused on computer-aided manufacturing (Andrade et al. 2002) techniques. This article starts with a brief introduction of tissue engineering (Bone tissue engineering and scaffolds) and scaffolding materials (Biomaterials used in bone tissue engineering). After a brief reviews on conventional scaffolding techniques (Conventional scaffolding techniques), a number of CAM techniques are reviewed in great detail. For each technique, the structure and mechanical integrity of fabricated scaffolds are discussed in detail. Finally, the advantaged and disadvantage of these techniques are compared (Comparison of scaffolding techniques) and summarised (Summary).
"A standard cytotoxicity assessment method set by the International Organization of Standardization (ISO 10993) was used. Similar procedures have been published elsewhere  . Briefly, extractant media are prepared by soaking the test or control materials in standard cell culture media (10% foetal calf serum, 1% L-glutamine and 0.5% penicillin/streptomycin) at a concentration of 0.2 g of material per ml of culture medium for 24 h at 37 • C and 5% CO 2 conditions in an incubator. "
[Show abstract][Hide abstract] ABSTRACT: In order to develop degradable elastomers with a satisfactory combination of flexibility and enzyme-mediated degradation rate, the mechanical properties, enzymatic degradation kinetics and biocompatibility of poly(xylitol sebcate) (PXS) has been systematically investigated in comparison with poly(glycerol sebacate) (PGS). Under the same level of crosslinked density, the PXS elastomer networks have approximately twice the stretchability (elongation at break) of their PGS counterparts. This observation is attributable to the relatively longer and more orientable xylitol monomers, compared with glycerol molecules. Although xylitol monomers have two more hydroxyl groups, we, surprisingly, found that the hydrophilic side chains did not accelerate the water attack on the ester bonds of the PXS network, compared with their PGS counterpart. This observation was attributed to a steric hindrance effect, i.e. the large-sized hydroxyl groups can shield ester bonds from the attack of water molecules. In conclusion, the use of polyols of more than three -OH groups is an effective approach enhancing flexibility, whilst maintaining the degradation rate of polyester elastomers. Further development could be seen in the copolymerization of PPS with appropriate thermoplastic polyesters, such as poly(lactic acid) and polyhydroxyalkanoate.
"Manufacture of binary or more complex biocompatible hybrid materials requires a compromise between specific mechanical performance, integrity and biological properties   . In particular , synthesis of enzymatic-cleavable material of an enhanced filler-matrix interaction is an important aspect of the biocomposites science    . "
[Show abstract][Hide abstract] ABSTRACT: Oxidised multi-wall carbon nanotubes (MWCNTs)–(R)-polylactide (PLA) composite was prepared in 85% yield via in-bulk Ring Opening Polymerisation (ROP) of (R,R)-lactide at elevated temperature using a ‘grafting-from’ technique. Outer nanotube walls were firstly covalently functionalised with a β-d-uridine linker—through the more reactive hydroxyl group (5′-OH)—enabling further a direct growth of the polymer from the free secondary hydroxyl groups (2′- and 3′-OH) present in the β-d-ribofuranose moiety. The morphology and chemical structure of the composite were comprehensively studied revealing a high-quality MWCNT-filler dispersion and loading of ca. 7 wt%, accompanied by a high molecular weight (Mw) of the (R)-PLA matrix equal to 116,700 Da. The presence of nanotube-filler affected the alignment of polymer fibrils in the composite. The elaborated approach may be implemented to a larger scale fabrication of biodegradable composites for medicinal applications or other functional materials where an enhanced matrix-filler interaction is required.
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