Functional Mesoporous Silica Nanoparticles with a Core-Shell Structure for Controllable Drug Delivery - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 58

(a)

TEOS TEOS/C18TMS

Hematite

Calcined

Reduced

Magnetic core

Mesoporous shell

(b) (c)

90
80

70

60

50

40
30
20

0 0203040
t (h)

50 60 70 80

FIGURE 3.5
(a) Illustration of synthesis of Fe 3 O 4 /Fe@nSiO 2 @mSiO 2 nanoparticles. (b) TEM image of Fe 3 O 4 /
Fe@nSiO 2 @mSiO 2 nanoparticles. (c) IBU release profile from Fe 3 O 4 /Fe@nSiO 2 @mSiO 2 nanopar-
ticles. (Reprinted with permission from Zhao W., Gu J., Zhang L., et al., J. Am. Chem. Soc. 127:
8916-8917, Copyright 2005, American Chemical Society.)

However, the aforementioned techniques are limited to synthesize mag-
netic mesoporous silica nanoparticles with poor magnetic response due
to the difficulty in increasing the amount of magnetic nanocrystals in the
whole nanoparticles (Kim et al. 2006, 2008; Lin and Haynes 2009). Recently,
many efforts have been made to synthesize magnetic silica nanoparticles
with large magnetic nanoparticle cores (≈100-200 nm) and mesoporous sil-
ica shells in order to increase the mass fraction of magnetic nanocrystals
(Zhao et al. 2005; Deng et al. 2008; Fu et al. 2010; Gai et al. 2011; Rosenholm,
Sahlgren, et al. 2011). Zhao et al. (2005) reported a novel strategy to fabricate
uniform magnetic nanoparticles with a magnetic core/mesoporous silica
shell structure (see Figure 3.5). Herein, uniform α-Fe 2 O 3 nanoparticles were
employed as the initial cores, a thin and dense silica layer was deposited on
the surface of α-Fe 2 O 3 nanoparticles in order to protect α-Fe 2 O 3 core from
leaching into the mother system under acidic circumstances. Then, meso-
porous silica shell was formed from simultaneous sol-gel polymerization