Biomedical Engineering Reference
In-Depth Information
100
80
60
40
20
0
0
10
20
30
40
50
Time (h)
FIGURE 9.5
Cumulative ibuprofen release from the two systems in the release media of different pH values.
■
and
▲
: pH 1.4 and 8.0 from hollow mesoporous silica spheres, respectively;
●
and
▼
: pH 1.4 and 8.0 from
PAH/PSS coated hollow mesoporous silica spheres, respectively. (Reprinted from Zhu, Y.F. et al.,
Angew.
Chem. Int. Ed.
, 44, 5083, 2005.)
increased to 8.0, the drug release rates from both systems were apparently different. The release
rate in pH 8.0 release medium was higher than that in the pH 1.4 medium because of the different
solubility of IBU in the release media of different pH values. IBU had a lower solubility in low
pH (
7) solutions. These results show the good
storage and sealing effect of the PAH/PSS multilayer coating on hollow mesoporous spheres in
pH 8.0 solution.
Wen and Chen et al. [26] prepared porous hollow silica nanoparticles (PHSNs) with various
shell thicknesses in the range of 5-45 nm and a pore diameter of 4-5 nm by a sol-gel route with two
different structure-directing templates. The shell thickness was controlled by adjusting the reactant
ratio of Na
2
SiO
3
·9H
2
O/CaCO
3
. These researchers investigated the loading and release properties
of avermectin in PHSNs and the UV-shielding property. PHSNs carriers had a remarkable loading
ability for avermectin (about 60.0% w/w); the amount of loaded avermectin decreased with increas-
ing shell thickness, while the UV-shielding property of PHSNs for avermectin improved as the shell
thickness increased. Increasing the shell thickness in the range of 5-45 nm led to a more sustained
release by decreasing the release rate of the pesticide from PHSNs, showing that the shell thickness
is one of the main controlling factors for the controlled drug release from such systems. Chen et al.
[27] prepared PHSNs with a diameter of 60-70 nm and wall thickness of approximately 10 nm by
using CaCO
3
nanoparticles as the inorganic template. The as-synthesized PHSNs were used as a
drug carrier to investigate
in vitro
release behavior of cefradine in simulated body fl uid. The experi-
ments showed that cefradine release behavior followed a three-stage pattern and exhibited a delayed
release effect.
Prasad et al. [28] reported a novel nanoparticle-based drug carrier for photodynamic therapy,
which could provide stable aqueous dispersion of hydrophobic photosensitizers, yet preserve the key
step of photogeneration of singlet oxygen, necessary for photodynamic action. Ultrafi ne organically
modifi ed silica-based nanoparticles (diameter of about 30 nm), entrapping water-insoluble photo-
sensitizing anticancer drug 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide, were synthesized in
the nonpolar core of micelles by hydrolysis of triethoxyvinylsilane. The entrapped drug was more
fl uorescent in aqueous medium than the free drug, permitting the use of fl uorescence bioimaging
<
7) solutions but was readily soluble in high pH (
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