Bioactive Glass-Based Scaffolds for Bone Tissue Engineering - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 213

(5 lm) BG-containing composites. The addition of bioactive glass nanoparticles
(n-BG) enhanced the Young's modulus by 50-100% to values of 1.2 and 1.6 GPa,
compared to both pure polymer films and the corresponding micro-sized BG
(m-BG)-containing films (10, 20, 30 wt%). The nanostructured surface topography
induced by n-BG considerably improved protein adsorption on the n-BG com-
posites compared to the unfilled polymer and the m-BG composites, whereas no
substantial differences in the proliferation of MG-63 osteoblasts were observed
between the different surfaces. It was thus confirmed that the addition of nanosized
bioactive glass particles had a more significant effect on the mechanical and
structural properties of a composite system in comparison with microparticles. The
addition of nanoparticles also enhanced protein adsorption, a desirable effect for
the application of composites in bone TE.
It has been also reported that tailoring porosity (e.g., nano- or mesoporosity)
and surface topography (e.g., by the incorporation of nanophase bioactive glass
particles into degradable polymer matrices) can favor protein adsorption and
cellular interactions [ 45 , 155 ], as well as improve the bioactive behavior [ 43 ],
antimicrobial/antibacterial effect [ 164 - 166 ] and mechanical properties [ 45 ]of
bioactive glass and related (composite) scaffolds.
6 Effect of Bioactive Glass on Angiogenesis
The ability of BG to stimulate the release of pro-angiogenic factors (e.g., VEGF)
from transplanted and/or host cells that have migrated into the scaffold might be
extremely beneficial in inducing neo-vascularization and rapid vascular in-growth
sufficient to meet the metabolic requirements of new bone. Enhancement of the
angiogenic potential of implantable biomaterials and scaffolds is crucial for the
success of tissue engineering approaches.
Despite increased evidence relating bioactive glass to angiogenic effects both
in vitro and in vivo [ 49 - 53 ], there has been limited research to date on under-
standing the specific role of bioactive glass in vascularization of bone scaffolds.
There is for example limited quantitative data regarding how the shape, size and
concentration of BG particles (e.g., as inclusion in polymer matrices) affect
angiogenesis. In addition, the influence of specific ions (as dissolution products of
bioactive glasses) on dissolution products of bioactive glasses on angiogenesis has
not been widely investigated. Moreover, the design criteria and the specific
requirements of the geometry and morphology of the scaffold (pore size distri-
bution, shape, interconnectivity) to achieve tailored scaffolds with angiogenic
properties are unknown [ 128 ]. A detailed overview of the available literature
investigating bioactive glasses with respect to angiogenesis has been published by
Gorustovich et al. [ 49 ], and the effect of ion release products concerning angiogenic
response has been reviewed by Hoppe et al. [ 9 ]. An important conclusion of the
literature analyzed is that cell culture studies demonstrated the pro-angiogenic potential
of BG over a limited range of BG concentrations, implying that dose-dependent effects