Biomedical Engineering Reference
In-Depth Information
diameter of the polymer-coated Si nanocrystals in PBS is measured by DLS
using the Zetasizer instrument. The particles are placed in the disposable capil-
lary cell at ~10 16 nanocrystals mL −1 concentration for light scattering measure-
ments. The Zetasizer detects the intensity of backscattered photons at a 173°
angle from an incident 4 mW He-Ne (633 nm) laser over a time interval of 10 s,
using a sample time (τ) of 0.5 µs. The hydrodynamic diameter is then extracted
from the light scattering data using the method of cumulants. 224 Using the same
sample, the zeta potential can be measured with the same instrument. The zeta-
sizer applies an alternating electric field across the cell that is equipped with two
electrodes. The particle mobility in the electric field is recorded as a phase shift
of an incident laser beam. This particle mobility is converted to zeta potential by
the Zetasizer software using the Smoluchowski theory.
2.7 CONCLUSIONS
This chapter provided an overview of the various NMs that are currently very
useful in nanomedicine. A few of the sNMs were provided with protocols for
synthesis, while others that are more well documented in some other refer-
ences were given an overview. There are NMs at their infancy and require
much more testing before their full potential in medicine can be realized. For
this reason, only a selected group of NMs that are well advanced in their medi-
cal applications were given much attention. In addition, selected current NM
characterization techniques were included to provide an overview of how the
properties of NMs are established. Again, there are many other techniques at
their infancy of development that were not included in this chapter. Instru-
ments that are useful for NM topography, chemical composition, size, and
shape analysis techniques of particular benefit to NM characterization were
discussed. For clearer and better understanding of NMs and their interactions
with biological systems for medical applications, novel high-resolution imag-
ing and analysis tools, which allow for easy sample preparation and in situ
monitoring, are still needed. 215
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2. Norris, D. J.; Sacra, A.; Murray, C. B.; Bawendi, M. G. Measurement of the Size-dependent
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