Biomedical Engineering Reference
In-Depth Information
FIGURE 3.1
Schematic of converting hydrophobic NMs to hydrophilic NMs loaded with a drug.
(For color version of this figure, the reader is referred to the online version of this topic)
or surfactants such as phospholipids.
51,52,63,64
All these strategies for surface mod-
ification result in surface functionalized water-soluble nanostructures.
For fluorescent tagging or labeling of relevant molecules for medical and bio-
logical applications, it is desirable to have water-soluble QDs and other NPs with
stable physical, electrical, magnetic, and/or optical properties that are not affected
by environmental factors. High-quality QDs, IOMNPs, and other NMs are often
synthesized under high-temperature organometallic conditions,
12,16,65
and are not
compatible with biological systems. This chapter is dedicated to the discussion
of various methods of surface modifications that convert NMs from hydrophobic
to hydrophilic form that allows them to be biocompatible and loaded with medi-
cally relevant molecules such as drugs or antibodies (Abs) or both (
Figure 3.1
).
3.2.1 Ligand Exchange
Ligand exchange is one of the methods by which the surfaces of NMs are
modified to make them water soluble in preparation for medical and biologi-
cal applications. A ligand may be in the form of an ion, atom, molecule, or
functional group that forms a complex with an NP, making up the interface
between the NMs or core/shell and its surroundings (
Figure 3.1
). Ligands play
a very important role in various applications of NMs that involve interactions
between the NM and its surroundings. There is a wide range of ligands for
NM ligand exchange, including hexanethiol, dodecanethiol, octadecanethiol,
