Biomedical Engineering Reference
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were not surrounded by fibrous connective tissue and no inflammation was
observed in vivo. They exhibit biologically stimulating properties. Below 10 μm, in
vitro phagocytosis and in vivo tissue inflammation was observed. Below 200 nm,
bioactivity decreased and particles diffused into internal organs of an animal
model and collected in both the respiratory and digestive systems.
Bioactive glass-ceramic nanoparticles (nBGC) have been prepared by the sol-gel tech-
nique based on polymerization reactions of metal alkoxide precursors (TEOS and/or TEP
mixture). The precursors are dissolved in a solvent, and a gel is formed by hydrolysis
and condensation reactions. Prior to hydrolysis calcium phosphate and/or antibacterial
compounds (e.g., silver nitrate) are added. The gel is subjected to a controlled thermal
process  to strengthen the gel by drying (aging temperature of 120ºC for 24 h) any liq-
uid by-products followed by thermal stabilization (500-800ºC for less than 6 h) to remove
any organic species from the surface of the material. Attractive forces between nano-
particles can cause agglomeration of particles, resulting in porosity among the particles
(Figure 9.19).
Nanofibers
Nanofiber-based scaffolds show great promise for tissue engineering applications due to
their inherent high porosities and surface-area-to-volume ratios. In addition, fiber diameters
(a)
(b)
×40.000 0.5 µm DFI/UFMS
×40.000 0.5 µm DFI/UFMS
(c)
(d)
×40.000 0.5 µm DFI/UFMS
×40.000 0.5 µm DFI/UFMS
FIGURE 9.19
Coatings composed of bioactive glass nanoparticles doped with (a) 0%, (b) 1%, (c) 3%, and (d) 5% silver to make
them antibacterial. (From Delben et al., J. Therm. Anal. Calorim. , 97(2), 433-436, 2009. With permission [59].)
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