Biomedical Engineering Reference
In-Depth Information
(a)
(a)
PAH/PSS
(b)
pH = 2
(c)
pH = 8
(e)
Low pH
(d)
Wa shing
100
(b)
(c)
80
Mesoporous shell
60
Hollow core
40
20
pH = 8.0
pH = 2.0
PAH/PSS multilayers
50 nm
0
0
10
20
30
Time (h)
40
50
60
FIGURE 3.3
(a) Scheme of polyelectrolyte multilayers (PEM) (consisting of PSS and PAH layers) coating on
HMS nanoparticles and pH-controlled loading and release of drug molecules. (b) TEM image
of PEM/HMS nanoparticles. (c) pH-controlled release switching of gentamicin molecules from
PEM/HMS system. (Reprinted from Zhu Y. and Shi J., Micropor. Mesopor. Mater. 103: 243-249,
2007, with permission from Elsevier Ltd.)
(PAH)] for controlling the drug release behavior. As shown in FigureĀ  3.3,
HMS nanoparticles are coated by a layer-by-layer (LbL) technique with
oppositely charged PAH and PSS alternatively. When this system is put in a
medium of low pH value, the PAH/PSS multilayers will open the pathways
for drug molecule diffusion into HMS nanoparticles. As the pH value of the
medium increases, PAH/PSS multilayers will close the pathways, and drug
molecules are loaded in HMS nanoparticles. To obtain the controlled drug
release, one simply puts the system loaded with drug molecules in a medium
of low pH value. In this way, the system not only has high drug-loading
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