Tissue Engineering And Nanotheranostics

“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics

Magnetic Nanohybrids for Magnetic Resonance Imaging 117

plays a vital role in the fabrication of Janus-colloidal nanoparticles,

which is a complicated interplay of factors like, entropy, enthalpy and

solution dynamics. The general ‘‘Janus’’ self-assembly principle is

summarized in Fig. 11, a ‘‘freezing-in’’ of the middle block (B) by

covalent or non-covalent cross-linking, while the mutually incom-

patible end blocks (A and C) point in different directions. The

preparation begins in most cases with the synthesis of the copolymers

in a common solvent, and upon change of solvent, the self-assembly

is induced. In the case of diblock copolymers, two combinations can

be chosen for the preparation of Janus particles. Either a combina-

tion of AB and BC diblock copolymers, in which the B segments are

insoluble in a given solvent and serve as the micellar core, or a mix-

ture of AB and CD diblock copolymers, where B and C have an

attractive interaction which forces the two polymers to coassemble is

used. In order to use ABC triblock terpolymers for the formation of

Fig. 10. Graphical representation of various types of complex hybrid nanostruc-
tures: (a) UCNP@SiO 2 @mSiO 2 &PMO composites,^63 (b) microphone-like structure
of AgCdSe−Au nanomaterials with average length of Au rod 41 nm and average size
of hexagonal AgCdSe being 24 nm,^64 (c) corresponding schematic model of Au–
Cu 2 S,^65 (d) Au–ZnO hexagonal nanopyramid-like structure,^66 (e) CoO-tipped CdSe/
CdS nanorods achieved after oxidation of the Co tips^67 and (f) CdSe/CdS/ZnS−Au@
hollow SiO 2 yolk/shell nanospheres.^68