Biomedical Engineering Reference
In-Depth Information
The characterization of nanoparticles for imaging usually starts with size mea-
surements and elemental analysis to warrant that the nanoparticles are formed as
planned and stay intact upon storage. Hence, Sections “Elemental analysis” and
“Size analysis” will provide an account of the general characterization methods
that are applied to almost all classes of nanoparticles. We will then describe sev-
eral more specialized methods for measuring the strength of the reporting signals
for the most common classes of imaging nanoparticles: nuclear (Section
“Radioactivity measurement of nanoparticles”), magnetic resonance imaging
(MRI) (Section “Magnetic properties of nanoparticles”), and optical (Section
“optical techniques”). The signal strength is used to compare the nanoparticles
and to evaluate the dosage for preclinical and clinical imaging studies. Sufficient
details will be provided regarding the corresponding hardware to help the reader
identify the right equipment for the specific project (Table 6.1). finally, we
highlight several emerging techniques that hold great potential in nanoparticle
characterization. Evaluation of specificity and activity of the nanoparticles
toward their biological targets will not be considered in this chapter; the readers
are referred to other chapters of this topic that provide a compelling account of
these topics.
6.2
elemeNtal aNalysis
The determination of composition and concentration of a nanoparticle sample is
often necessary for biomedical applications where dosage and toxicity effects may
be of concern. a variety of elemental analysis methods are used to both determine the
presence of an element in a sample and quantify how much of said element is pre-
sent. While these methods are most commonly employed for inorganic particle types,
they may also be used for some organic particles. In addition to characterizing a
nanoparticle sample itself, these elemental analysis methods can be used to charac-
terize the retention of nanoparticles within tissues and biological fluids, making them
useful for bioretention, toxicity, and localization studies.
Elemental analysis by atomic spectroscopy techniques is commonly used for bio-
medical particles containing metals such as gold, silver, copper, manganese, gado-
linium, iron, etc. The most frequently employed atomic spectroscopy techniques are
inductively coupled plasma mass-spectrometry (ICP-MS) and inductively coupled
plasma optical emission spectrometry (ICP-oES). Both techniques are capable
of simultaneous detection and high-precision quantification of most metal and non-
metal elements in a liquid sample. Typically, nanoparticle samples are dissolved
in an acid solution before analysis. The intensity of the signal produced by analytes
of interest in the dissolved sample is compared to the signals of a set of external cal-
ibration standards of known concentration in order to determine the concentration
in mass per volume units of the sample. When concentration data on particles is
combined with size and morphology information, it is often possible to estimate the
concentration in terms of particles per volume.
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