Tissue engineering, polyesters

In order to develop a tissue-engineered heart valve, a group at Children s Hospital in Boston evaluated several synthetic absorbable polyesters as potential scaffolding materials for heart valves. Unfoitu-nately, the most synthetic polyesters proved to be too stiff to be function as flexible leaflets inside a tri-leaflet valve. " In the late 1990s, a much more flexible PHAs called poly-3-hydroxyoctanoate-co-3-hydroxyhexanoate (PHO) was used as the scaffold material for the valve leaflet, and then the entire heart valve. ... 

Webb A, Yang J, and Ameer G. Biodegradable polyester elastomers for tissue engineering. Exp Opin Biol Ther, 2004, 4(6), 801-812. 

To minimize or eliminate reliance on ethylene oxide and exploit reliability of assured sterility using radiation for absorbable polymers and particularly those used in tissue engineering, Shalaby and co-workers developed the radiochemical sterilization (RC-S) process. The RC-S process represents a novel approach to the sterilization of certain mechanical devices, such as those made of absorbable polyesters, that are sensitive to high-energy radiation delivered at the traditional dose of 25 kGy. RC-S is a hybrid process encompassing the attributes of chemical high-energy radiation sterilization without the drawbacks associated with the use of the parent processes. RC-... 

Selection of a tissue engineering substrate includes a choice between absorbable and nonabsorbable material, as well as a choice between synthetic and naturally derived materials. The most common synthetic polymers used for fibrous meshes and porous scaffolds include polyesters such as polylactide and polyglycolide and their copolymers, polycaprolactone, and polyethylene glycol. Synthetic polymers have advantages over natural polymers in select instances, such as the following i... 

Polyesters have also been processed into tubular form for orthopedic and cardiovascular tissue engineering applications. Meinig and co-workers evaluated bone regeneration using tubular PLLA membranes in mid-diaphyseal defects in rabbit radii. The membrane prevented soft tissue formation in the defect area, and it allowed woven bone to fill the defect. Local inflammation or systemic intolerance was not observed, and the membranes remained intact for the entire 64-week study. 

In addition to the release of acidic degradation products, another deficiency of polyesters used in tissue engineering is their lack of functional groups. To improve biocompatibility of PLLA and PGA, some researchers have processed these polyesters with amino acids such as glycine and lysine. - ... 

Aliphatic polyesters (such as PLA, polyglycolic acid and their copolymers) are the most important class of biocompatible polymers used in biomedical applications. This class of polymers has shown superior properties over conventional polymers, such as excellent biocompatibility, biodegradation, and thermal, physical and mechanical properties, which make them suitable for applications in drug delivery and tissue engineering [19-21]. 

The Role of Linear Aliphatic Biodegradable Polyesters in Tissue Engineering and Regeneration... 

Electrospinning of PHA is still relatively new in scaffold fabrication. To date, P(3HB) and P(3HB-co-3HV) are the most common microbial polyesters to be electrospun into tissue-engineering scaffolds. Suwantong et al. (2007) prepared ultrafine electrospun fiber mats of P(3HB) and P(3HB-co-3HV) as scaffolding materials for skin and nerve generation, hi their study, they evaluated the in vitro biocompatibility of these fibers using mouse fibroblasts and Schwann cells... 

Several types of bacterial polyesters that are produced by biosynthesis are poly-3-hydroxybutyrate, poly-4-hydroxybutyrate, poly-3-hydroxyvalerate, poly-3-hydroxyhexanoate, poly-3-hydroxy-heptanoate, etc., and their respective copolymer combinations. Due to their ability to degrade naturally in variety of environments, they will find a lot of applications in disposal items, short-term packaging, and also considered biocompatible in contact with living tissues and can be used for biomedical applications (e.g., drug encapsulation, tissue engineering) (Chauhan, 2012). 

As non-degradable polyesters are quite common as textile materials, it comes as no surprise that their degradable counterparts are also readily processable into fibres. Polymer fibres are particularly interesting for biomedical applications, including wound dressings, controlled-release formulations and tissue engineering. Several spinning techniques result in the formation of polymer fibres. 

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