Bioactive Glass-Based Scaffolds for Bone Tissue Engineering - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 209

Fig. 7 Histology of porous BG scaffolds after 5 weeks of implantation in New Zealand rabbits
[ 137 ]. a New vasularization formed with the fibrous tissue band of the capsule (arrow).
b Collagen fiber strands (asterisk) are distributed throughout the scaffold material showing new
blood vessel formation (arrow). (Figures reprinted with permission of Springer)

made from porous glass, they are normally inherently brittle and have poor
fracture toughness (Table 2 ).
Fracture toughness values in the range reported for cortical bone (2-12 MPa m 1/2 )
are required for load-bearing applications and therefore toughening effects must
be introduced into this type of scaffold, which can be achieved by producing
composites [ 34 ]. Polymer/bioceramic composite scaffolds thus represent a
convenient alternative due to the possibility of tailoring their various properties
(e.g., mechanical and structural behavior, degradation kinetics and bioactivity)
[ 34 , 139 ]. Composites made of polymers and bioceramics combine the advantages
of their individual components [ 3 , 34 , 109 ]. Polymers exhibit generally high
ductility, flexibility and favorable formability as well as processibility and plas-
ticity. The glass or glass-ceramic phase adds stiffness and adequate mechanical
strength to the composite. In particular, composites based on biodegradable
polymers and bioactive glasses are being increasingly studied as bone TE materials
because this particular combination does not require a revision surgery for their
removal, since newly formed bone gradually substitutes the implanted scaffold
during degradation [ 34 , 37 ]. Much current research is therefore focused on the
fabrication of bioactive composite materials with bioactive glass incorporated either
as filler or coating (or both) into the bioresorbable polymer matrix [ 34 ]. Effort is
devoted in particular to the development of porous, high-strength composite struc-
tures for the regeneration of human bone at load-bearing sites. A comprehensive
general review on bone TE scaffolds based on composites with inorganic bioactive
fillers has been published by Rezwan et al. [ 34 ]. The state of knowledge on polymer-
bioceramic composites with focus on polymer coatings and interpenetrating poly-
mer-bioceramic structures for bone TE has been summarized by Yunos et al. [ 140 ].
Polymer/bioactive glass nanocomposites, based on bioactive glass nanoparticles and
nanofibres, have been reviewed by Boccaccini et al. [ 42 ].
Many studies have been carried out in the last 10 years to optimize and
investigate

bone TE composite scaffolds concerning material combinations,