Biomedical Engineering Reference
In-Depth Information
FIGURE 5.2
DLS data for water-soluble 30-nm IOMNPs that are encapsulated with amphiphilic
polymers that have carboxyl groups making them water soluble.
Courtesy of Ocean NanoTech.
(For color version of this figure, the reader is referred to the online version of this topic)
A portion of the dynamic light scattering (DLS) data for 30-nm iron oxide
magnetic nanoparticle (IOMNP) with carboxyl groups on the surface is shown
in
Figure 5.2
. The DLS data sheet provides an average size based on volume,
area, or diameter measurement. It also provides a particle size distribution
along with the smallest size to the biggest size. Another parameter provided by
the full DLS data is the average zeta potential of the NMs. The 30-nm IOMNPs
(Ocean NanoTech, Catalog # SHP 30) have an average zeta potential between
−30 and −50 mV.
5.3.2 Particle Size and Size Distribution
Particle size and size distribution are the most important characteristics because
these determine the chemical and physical properties of NMs. Most semi-
conductor and metal NMs are synthesized in organic solvent and initial size
characterizations are performed on the core or core/shell particles before these
are converted into the water-soluble form. The core or core/shell size and size
distribution (
Figure 5.3
) is usually measured with transmission electron micros-
copy (TEM, Chapter 2). Depending upon the sophistication of the instrument,
the TEM results can provide a statistical analysis of the NMs' size distribution.
In cases when the TEM does not provide size distribution, the software ImageJ
has been used to calculate particle size distribution from a TEM image.
In order for the NMs to be useful for biological applications such as
drug delivery, they need to be converted into water-soluble forms in order
to be biocompatible. Conversion into the water-soluble form is done through
amphiphilic coating (Chapter 2, Section 2.1). The size and size distribution
of the water-soluble forms (
Figure 5.2
) of the NMs are established using
DLS (Chapter 2, Section 2.4.5).
Currently, the fastest and most routine method of determining NMs' size is
by photon correlation spectroscopy or DLS. Photon correlation spectroscopy
