Biomedical Engineering Reference
In-Depth Information
possible mechanism of slow drug release kinetics of MBG is due to the exis-
tence of a large number of Si-OH groups in MBG, which plays an important
role in interacting with drugs and proteins (Xia and Chang 2006). Further
study has found that the drug release from MBG is mainly controlled by a
Fickian diffusion mechanism (Zhu and Kaskel 2009; Wu and Chang 2012).
Several methods were used to control drug and growth factor delivery in
MBG sphere and scaffold systems. In MBG sphere system, we harnessed their
apatite mineralization ability of MBG materials and coprecipitated bovine
serum albumin (BSA) with apatite on the surface of MBG spheres. It was
found that the BSA-loading efficiency of MBG was significantly enhanced
by coprecipitating with apatite, and the loading efficiency and release kinet-
ics of BSA could be controlled by controlling the density of apatite formed
on MBG microspheres (Wu, Zhang, Ke, et al. 2010). Drug delivery could be
controlled by using different bioactive materials with different degradation.
Three bioactive material powders—MBG, nonmesoporous bioglass (BG),
and hydroxyapatite (HAp)—were incorporated into alginate microspheres,
respectively, and loaded with drugs. Results showed that the drug-loading
capacity was enhanced with the incorporation of these materials into alginate
microspheres. The MBG/alginate composite microspheres had the highest
drug-loading capacity. Drug release from alginate microspheres correlated to
the dissolution of MBG, BG, and HAp in PBS, and pH was a key factor in con-
trolling the drug release; a high pH resulted in greater drug release, whereas
a low pH delayed drug release (Wu, Zhu, et al. 2010). To further control drug
delivery in MBG scaffold system, drugs were loaded into MBG scaffolds and
then modified scaffolds by using silk protein, which formed a thin silk layer
on the surface of pore walls. The silk layer can efficiently inhibit the burst
release of drugs from MBG scaffolds (Wu, Zhang, Zhu, et al. 2010).
MBG scaffolds have been investigated for the delivery of VEGF. It was
found that MBG scaffolds have significantly higher loading efficiency and
more sustained release of VEGF than nonmesoporous bioactive glass scaf-
folds. Our study suggests that the mesopore structures in MBG scaffolds
play an important role in improving the loading efficiency and decreasing
the burst release of VEGF (Wu, Fan, et al., forthcoming).
1.3.2 Drug and Growth Factor Delivery in MBG for
Antibacteria and Tissue-Stimulation Application
Although there are a great number of studies for the delivery of drugs by
MBG, there are few studies for the functional effect of drug and growth fac-
tor delivery from MBG. Our group has recently investigated the antibacte-
ria and cell-stimulating function of drug loaded MBG. Drug ampicillin was
loaded into MBG nanospheres and scaffolds and then exposed to
E. coli
(DH5α) for different time periods. It was found that the sustained release of
ampicillin from MBG revealed significant antibacteria effect (see Figure 1.6).
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