Synthesis of Nonspherical
Mesoporous Silica Ellipsoids
with Tunable Aspect Ratios for Magnetic Assisted Assembly and Gene
Delivery
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Abstract
Despite the extensive application of ellipsoidal micro-/nanoparticles,
the synthesis of shape anisotropic ellipsoids is rare because of the
minimization of surface free energy that favors simple spherical shape
rather than complex nonspherical shape. We present the synthesis of
silica ellipsoids with hexagonal mesostructure via the organic–inorganic
cooperative assembly in the presence of cosolvents (KCl and ethanol).
The aspect ratio of ellipsoids can be tuned systematically by controlling
the concentration of ethanol. Transmission electron microscopy (TEM)
shows that the ellipsoid possesses one-dimensional (1-D) pore channels
parallel to the major axis, and the electron tomography (ET) technique
shows that the ellipsoid has indeed hexagonal prism morphology in
the middle and ellipsoidal morphology at two tips. A mechanism for
the formation of mesoporous silica ellipsoids has been proposed. Importantly,
magnetite/silica composite ellipsoids were prepared through a nanocasting
route and can be used as building blocks to organize into ordered
arrays in response to an external magnetic field. In addition, after
functionalized with amino-groups, the amino-modified anisotropic magnetite/silica
ellipsoids can be further used as carriers for delivering oligo-DNA-Cy3
into tumor cells, showing potential in directed self-assembly and
drug/gene delivery