Functional Mesoporous Silica Nanoparticles with a Core-Shell Structure for Controllable Drug Delivery - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 64

Rattle-type magnetic mesoporous silica nanoparticles have also been pre-
pared through a sol-gel approach associated with water-in-oil microemul-
sions as templates (Lin et al. 2009; Liu et al. 2010; Tan et al. 2010; Zhang
et al. 2011). The nanoparticle morphology, the loading density of magnetic
nanocrystals, and the size of the pores can be controlled by adjusting the
experimental parameters. Zhang et al. (2008; Liu et al. 2010) reported the
preparation of rattle-type periodic mesoporous organosilica magnetic hol-
low sphere (PMO-MHS) by embedding monodisperse magnetic nanocrys-
tals or large magnetic particles (≈200 nm) into the cavities of highly ordered
PMO hollow spheres. In addition, uniform and well-dispersed rattle-type
Fe 3 O 4 @SiO 2 nanoparticles of around 50 nm can be prepared through a bio-
inspired silicification approach at room temperature and a near-neutral
pH aqueous environment (Tan et al. 2010). All these rattle-type magnetic
mesoporous silica nanoparticles show the potential for application in con-
trollable drug delivery.
3.3.2 Luminescent Mesoporous Silica Nanoparticles
for Controllable Drug Delivery
It is well known that luminescent labeling is a real-time, simple, and effective
way to monitor the route of drug-transport carriers in a living system. Drug
delivery systems with luminescent labels can easily evaluate the efficiency of
the drug release and disease therapy (Insin et al. 2008). As mentioned earlier,
mesoporous silica nanoparticles are promising carriers for drug delivery.
Therefore, the combination of mesoporous silica and luminescent labels to
design luminescent mesoporous silica nanoparticles for drug delivery sys-
tems has become a hot research topic.
Traditionally, organic dyes, such as fluorescein isothiocyanate (FITC), rho-
damine, and cyanine dyes, are the most common used biological lumines-
cent labels. However, dye molecules usually suffer from photobleaching and
quenching when exposed to harsh environments due to interactions with
solvent molecules and reactive species such as oxygen or ions dissolved in
solution (Wang et al. 2006). Therefore, they are limited for sensitive detec-
tion and real-time monitoring. Many efforts have been made to overcome
the drawbacks. One of the most promising strategies is to form a core-shell
structure that contains a nonporous dye-doped silica core and a mesoporous
silica shell, which also processes sustained drug release property and good
compatibility (Wang et al. 2009; Lei et al. 2011). As shown in Figure 3.9, Lei et
al. (2011) reported a monodisperse multicolor core-shell nanoparticle, using a
triple-dye-doped silica nanoparticle as the core and mesoporous silica as the
shell. The preparation of multicolor core-shell nanoparticles includes (1) the
premodification of the dye molecules: 3-aminopropyltriethoxysilane (APTS)
reacts with fluorescein isothiocyanate (FITC), rhodamine B isothiocyanate
(RBITC), and rhodamine 101 succinimide (R101-SE) to form three types of
dye-APTS conjugates; (2) the hydrolysis and co-condensation of dye-APTS