Biomedical Engineering Reference
In-Depth Information
MCM-48, and SBA-15 (Yan et al. 2007; Yang et al. 2008; Huang et al. 2010).
However, this method inevitably blocks the pores to some extent, resulting
in the influence on drug loading and release from the carriers.
Recently, more efforts have been made to form a core-shell structure by
coating phosphor core with mesoporous silica shell, which reduce the inter-
ference of the environment on the luminescent property of the phosphor core
and completely utilize the excellent advantages of mesoporous silica matrix.
Different RE-doped phosphor cores, such as Y
2
O
3
:Eu, CeF
3
:Tb, Gd
2
O
3
:Eu,
LaF
3
:Y b/E r, N aY F
4
:Yb/Er, and Gd
2
O
3
:Er, have been coated with mesopo-
rous silica shell (Kong et al. 2008; Gai, Yang, Hao, et al. 2010; Yang et al.
2010; Kang et al. 2011; Xu, Gao, et al. 2011; Xu, Li, et al. 2011). All the systems
exhibit sustained drug release profiles and excellent luminescent proper-
ties. For the core-shell structured up-conversion luminescent and mesopo-
rou s NaY F
4
:Y b
3+
/Er
3+
@nSiO
2
@mSiO
2
nanoparticles, they were successfully
prepared by coating nonporous and further mesoporous silica layers with
different thickness on NaYF
4
:Y b
3+
/Er
3+
nanoparticles via a facile two-step
sol-gel process as shown in FigureĀ 3.10 (Kang et al. 2011). The nanoparticles
exhibit little cytotoxicity, and the
in vitro
release of IBU from the core-shell
luminescent mesoporous silica nanoparticles shows a release profile in two
steps: an initial diffusion-controlled release, followed by a slower release rate.
Furthermore, upon excitation by a 980 nm near-infrared laser, the nanopar-
ticles emit green and red fluorescence of Er
3+
even after the loading of IBU.
Interestingly, the drug release amount and process can be monitored by the
change of the up-conversion emission intensity. Yang et al. (2010) fabricated
LaF
3
:Y b
3+
/Er
3+
@
n
SiO
2
@
m
SiO
2
nanoparticles with a uniform particle diam-
eter of 130 nm. The inner luminescence core endues the nanoparticles with
up-conversion properties. The outer mesoporous silica shell load IBU in the
channels, and most of the incorporated drug molecules can be released to the
SBF in 70 h. Therefore, these preliminary results indicate that the luminescent
mesoporous silica nanoparticles with a core-shell structure have potential
applications in the fields of drug delivery and disease therapy.
3.3.3 Multifunctional Magnetic-Luminescent Mesoporous
Silica Nanoparticles for Controllable Drug Delivery
As discussed earlier, both magnetic and luminescent mesoporous silica
nanoparticles are of great multifunctional platforms for smart biomedical
applications. It can be imagined that the combination of magnetism and
luminescence in one mesoporous silica nanoparticle provides a new gen-
eration mesoporous silica carrier with a broad range of functionalities. For
example, magnetic-luminescent mesoporous silica nanoparticles can serve
as an all-in-one diagnostic and therapeutic tool, which could be used to visu-
alize and simultaneously treat various diseases.
Yang et al. (2009; Gai, Yang, Li, et al. 2010) designed the core-shell magnetic-
luminescent mesoporous silica nanoparticles using nonporous silica-coated
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