Biomedical Engineering Reference
In-Depth Information
making it a candidate for fracture fixation [228]. Composites for cortico-
cancellous bone grafts were also made from P3HB-7%3HV and HA [229].
Composites made from P3HB-7%3HVandTCPshowedagoodbiocom-
patibility in the femur of rabbits. However, PLLA/TCP was regarded as more
suitable for fracture support due to accelerated degradation, thereby main-
taining the required strength for a bone healing time of about 6 weeks [184].
In vitro studies have shown the formation of bone-like apatite on the surface
of P3HB/HA [230] and P3HB-12%HV/TCP [231] composites. Recently, the
fabrication and properties of P3HB-3%3HV/wollastonite composite scaffolds
have been reported [189, 232].
In vitro studies using bone marrow cells have shown the potential of
P3HB and P3HB-8%3HV matrices for bone tissue engineering (see Sect. 3.2).
A chemically synthesized degradable polyesterurethane foam containing
crystalline domains of short-chain P3HB and amorphous domains of PCL
exhibits good osteoblast compatibility and is being considered as scaffold
material for bone repair [233].
The potential of P3HB films and scaffolds as matrices for cartilage regener-
ation have been extensively studied in vitro (see Sects. 3.2 and 5.2). Thus for
example, nanofibrous polymer mats have been fabricated by electrospinning
of P3HB-5%3HV solution and tested as potential scaffolds for chondrocyte
attachment [133]. However, animal studies have not yet been reported.
Other Tissue Engineering Applications
P3HB films [234] and P3HB-coated textiles [235] have been described as ma-
terials for wound covering. Nonwoven P3HB “wool” has been developed as an
internal wound scaffolding device that supports reepithelialization [236].
P3HB surface-modified by ammonia plasma has been examined as a re-
placement material for respiratory mucosa after surgical resections in the
trachea, nasal septum, or sinus maxillaris [136]. P3HB-8%3HV modified by
oxygen plasma has been tested as a temporary substrate for retinal pigment
epithelium cells, to treat retinal disorders caused by retinal pigment epithe-
lium degeneration [137].
4
Poly(4-hydroxybutyrate)
and Poly(3-hydroxybutyrate- co -4-hydroxybutyrate)
P4HB is a thermoplastic polyester that can be produced by a number
of microorganisms, including Alcaligenes eutrophus strains [237-239], Co-
mamonas acidovorans [240], Hydrogenophaga pseudoflava [241], and re-
combinant Escherichia coli [47, 242, 243], using substrates such as 4-hy-
droxybutyrate, 4-hydroxybutyrolactone, or 1,4-butanediol. P3HB-4HB can be
obtained by fermentation using microorganisms such as Alcaligenes eutro-
 
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