Polyhydroxyalkanoates for tissue engineering

Polyhydroxyalkanoates (PHA), polyesters produced by microorganisms under unbalanced growth conditions (Doi 2002) have potential applications for medical and pharmaceutical purposes. The primary factor is because of their biodegradability. Nevertheless other favorable qualities such as their adaptability to suit the requirements of different applications, non-toxicity and thermoprocessibility properties have propelled their uses as tissue engineering biomaterials. Polyhydoxyalkanoates (PHA) and its composites include poly 3-hydroxybutyrate (PHB), copolymers of 3-hydroxybutyrate and 3-hydroxyvale-rate (PHBV), poly 4-hydroxybutyrate (P4HB), copolymers of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx) and poly 3-hydroxyoctanoate (PHO) (Hrabak 1992). PHA has been utilized to develop devices like sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples, screws (including interference screws), bone plates and bone plating systems, surgical mesh, repair patches, slings, cardiovascular patches, orthopedic pins (including bone.lling augmentation material),adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defectw1l1x repair devices, pericardial patches, bulking and .lling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, liga-ment and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, wound dressings, and hemostats (Chen & Wu 2005). As PHA composes of various hydroxyalkanoates that are synthesized by as many as 75 different genera of gram-positive and gram-negative bacteria, an extensive group of properties are available (Reddy et al 2003). Non-storage PHA, poly(3HB) have been found in the cytoplasmic membrane and cytoplasm of Escherichia coli, as well as in yeasts, plants and animals. The mechanical and biocompatibility of PHA can also be changed by blending, modifying the surface or combining PHA with other polymers, enzymes and inorganic materials, making it possible for a wider range of applications There are several different pathways for PHA formation. "Source":[ http://tissue.medicalengineer.co.uk/Polyhydroxyalkanoates+for+tissue+engineering.php?page=1].

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