As an increasing number of studies use gold nanoparticles (AuNPs) for potential medicinal, biosensing and therapeutic applications, the synthesis and use of readily functional, bio-compatible nanoparticles is receiving much interest. For these efforts, the particles are often taken up by the cells to allow for optimum sensing or therapeutic measures. This process typically requires incubation of the particles with the cells for an extended period. In an attempt to shorten and control this incubation, we investigated whether nanosecond pulsed electric field (nsPEF) exposure of cells will cause a controlled uptake of the particles. NsPEF are known to induce the formation of nanopores in the plasma membrane, so we hypothesized that by controlling the number, amplitude or duration of the nsPEF exposure, we could control the size of the nanopores, and thus control the particle uptake. Chinese hamster ovary (CHO-K1) cells were incubated sub-10 nm AuNPs with and without exposure to 600-ns electrical pulses. Contrary to our hypothesis, the nsPEF exposure was found to actually decrease the particle uptake in the exposed cells. This result suggests that the nsPEF exposure may be affecting the endocytotic pathway and processes due to membrane disruption.
The exposure of nanosecond pulsed electric fields (nsPEF) to living cells has been shown to create nanopores in the
plasma membranes. These nanopores allow the passage of small ions but exclude the transport of larger molecules
such as Propidium ions, with permeabilization persisting for many minutes. To characterize these nanopores and the
effect of temperature of the formation and resealing of these pores, we have chosen to use 6-Propionyl-2-(N,NDimethylamo)
Naphthalene (PRODAN) as an indicator of membrane organization. PRODAN is a fluorescent dye
with a large excited-state dipole moment that displays extensive solvent polarity-dependent fluorescent shifts. By
monitoring this shift in fluorescence spectrum, disruption of the membrane after an electric exposure is observed as
an immediate increase in the membrane fluidity, likely indicating poration of the membrane. High-speed imaging
results indicate that a change in membrane organization occurs instantly (<5 ms), with longer pulse widths having a
more dramatic effect on the membrane. This instantaneous membrane disruption was shown to recover within 500
ms.
Several studies, over recent years, focus on the use of chitosan, a biocompatible macromolecule, to form gold
nanoparticles (GNPs). In this study, gold nanoparticles were synthesized using chitosan and Chloroauric acid, under
stirring which cause micro/nano-gels to form. Ultraviolet (UV) light is used to reduce solution into gold nanoparticles,
in which the resulting nanoparticles are biocompatible after this reduction. In effort to obtain nanoparticles of different
shape and size using the chitosan, different concentrations of monovalent salt, were added to the chitosan solution. The
different signatures of the particles based on the concentration of the salt in the solution are observed using an optoacoustic
setup to detect morphological changes in the particles due to shifts in the absorption resonance. The optoacoustic
measurements are compared to the absorption spectra of the gold nanoparticles. The overall goal of this study
is to investigate the influence of chitosan, with the addition of the monovalent salt, on the formation
of the biocompatible gold nanoparticles. This characterization will aid in the preparation of measurements to take on
these particles in other portions of the electromagnetic spectrum such as radio frequencies.
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