“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics
Magnetic Nanohybrids for Magnetic Resonance Imaging 105
Oberdörster group also proposed the inverse relationship between
the particle size and the number of the atoms or molecules on the
surface of a spherical nanoparticle.^17 For a nanoparticle of 30 nm
diameter, approximately <10% of its constituent atoms/molecules are
located on the surface, whereas for a particle of 3 nm diameter about
80% of its atoms/molecules are situated on the surface (2). Therefore,
nanoparticles of less than 50 nm have been showing outstanding
properties for numerous applications because of the atoms/molecules
positioned on their surface.^17 Therefore, small nanosized particles
combined with imaging and therapeutic agents have been presenting
innovative prospects in current bionanotechnology.
This chapter reviews the magnetic nanoparticles, the properties of
magnetic nanoparticles, magnetic nanohybrids, fabrication of mag-
netic nanohybrids, and theranostic biomedical applications of the
magnetic nanohybrid materials. Further, the functionalizations of
these magnetic hybrid structures with silica coatings and amphiphilic
polymer are illustrated. Finally, the functions of biomolecule conju-
gates on the surface of magnetic nanohybrids which offer cellular
targeting and utilize them as multimodal bioprobes for MRI, drug
delivery and phototherapy are highlighted.
2. Magnetic Nanohybrids
Magnetic hybrid nanostructures can be defined as a mixture of two or
more components embedded together with magnetic material to
form a single system which delivers enhanced multifunctional proper-
ties because of its hybridization nature, such as proper arrangement
of a magnetic nanoparticle attached on to the tip of a nanorod can be
the foundation for various complex heterostructures, e.g. dumbbells,
shuttles, chains, microphone, and star shapes. The capability of
designing a variety of hybrid nanomaterials is entirely related to the
physiochemical, external, and internal interfacing properties of indi-
vidual components. Besides the primary development in fabrication,
curiosity develops to investigate the synergetic properties of HNPs
which usually generate at the colloidal boundaries of nanoparticles.
Furthermore, the surface of these magnetic nanohybrid structures is
modified with biodegradable materials such as silica, targeting ligands
