Biomedical Engineering Reference
In-Depth Information
drug molecules. Zink's groups developed several functional mesoporous
silica-based pH-responsive controlled drug release systems utilizing the pH-
dependent pseudorotaxanes, rotaxanes, or other analogues (Patel et al. 2008;
Du et al. 2009; Meng et al. 2010). For example, the aromatic amine stalks were
immobilized on the surface of mesoporous silica nanoparticles, and mac-
rocyclic movable gates β-cyclodextrin (β-CD) were introduced to encircle
the stalks as a result of noncovalent bonding interactions under neutral pH
conditions, and effectively block the nanopore openings for drug storage.
Decreasing the pH under mildly acidic conditions leads to protonation of
the aromatic amines and dissociation of β-CD caps, following drug mod-
els diffusion from the nanopores (see Figure 3.13) (Meng et al. 2010). For
liner molecular gatekeepers, stimuli-responsive linear supramolecules are
anchored to the external surface of mesoporous silica nanoparticles, and
the “close/open” mechanism arises from “across/parallel or shorten” of the
liner molecules (Casasús et al. 2008; Bernardos et al. 2010; Coll et al. 2011).
For example, Du et al. (2009) tethered the well-known pH-responsive linear
polyamine molecules on the pore outlets of MCM-41 nanoparticles through
covalent bonds, resulting in both pH-controlled and anion-controlled gate-
like effects. The pH-controlled open/close mechanism arises from hydrogen
bonding interactions between amines at neutral pH and Columbic repul-
sions in closely located polyammoniums at acidic pH. The anion-controllable
response can be explained in terms of anion complex formation with the
tethered polyamines.
3.4 Conclusion and Outlook
In this chapter, the recent research progress on functional mesoporous
silica nanoparticles with a core-shell structure for controllable drug deliv-
ery was highlighted. A variety of advanced synthetic strategies have been
developed to construct functional mesoporous silica nanoparticles with a
core-shell structure, including hollow mesoporous silica nanoparticles, mag-
netic and luminescent core-shell mesoporous silica nanoparticles, and other
multifunctional core-shell mesoporous silica nanoparticles. Meanwhile,
multifunctional drug delivery systems based on these nanoparticles have
been designed and optimized in order to deliver the drugs into the targeted
organs or cells, with a controllable release fashion by virtue of various inter-
nal and external triggers. The systems will be able to track the released drug
molecules in a living system. These developments are encouraging and show
great promise in biomedical applications.
However, there are still many challenges that need to be overcome and
investigated more comprehensively and thoroughly for these functional
mesoporous silica nanoparticles to advance its biological and biomedical
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