Combinatorial effects of functional nanoparticles and electromagnetic stimulation on cells




Franklin, Samantha

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With the increasing development and use of nanomaterials in science, it is important to thoroughly measure their effects in biological systems. For nanomaterials to be applied, they must have various properties and characteristics that are field specific, such as biocompatibility and plasmon peaks that are beneficial to the excitation source. The simplest form of measuring these properties and interaction is in vitro. While in vivo systems contain three-dimensional tissue structures that may interact in a slightly different way than cell culture (in vitro), it is important to have general knowledge of the effect of these nanomaterials on cells. There are different methods to synthesizing nanomaterials; more specifically gold nanoparticles (AuNPs). These synthesis techniques have their advantages and disadvantages. Some of these are control of the particle shape and size, surface modification, and toxicity issues. Sodium Citrate (NaCit) AuNPs are the most commonly synthesized. They result in spherical particles with a size distribution of 10-20 nm. Studies have shown that there is slight control over particle size with added heating, during the synthesis, but the size distribution increases. Gold particles have valuable properties, one of them being a localized surface plasmon resonance (LSPR). The utilization of this LSPR is significant for tissue studies, since it is the wavelength that the electrons on the surface of the particles respond to upon excitation. Gold nanorods (AuNRs) have a red-shifted resonance due the longitudinal formation, as well as spherical resonance. Currently, the common method used for AuNR formation is by seed mediated growth with a reactant that is toxic to cells. Neuronal cells have been revealed to have response to stimulation of light. The cellular response has been measured as good (increased cell growth) and bad (DNA damage and apoptosis), depending on wavelength utilized. Although it is known that an external stimulation can be applied to measure neuron response, it is vital to understand the mechanism that occurs at a cellular level. To overcome some of these current limitations and the use of gold nanoparticles upon stimulation, various efforts were made to create a gold nanoparticle for both viable and non-viable biological applications. First, gold nanoparticles were synthesized in the presence of a macro-molecule, chitosan, to assist in stabilization and reduction of gold nanoparticles, denoted Chit-AuNPs. Surfactants were added to the solution, which resulted in moderate control of particle shape and size, with sphere formation as small as 2 nanometers (nm) and necklacing of particles that resonate like AuNRs. Secondly, cells in the presence of Chit-AuNPs were stimulated externally with a short electrical pulse to enhance nanoparticle uptake. While there was no significant uptake, it was determined that the pulses, and possibly the particles, blocked the uptake mechanism of the cell (endocytosis process). Next, a low power (~0.5W/cm 2), nanosecond pulsed laser was used to measure the effects of the particles in neurons. It was determined that there were no negative effects from either the particles or the laser stimulation. A significant increase in cell growth was measured post exposure. Finally, AuNPs were stimulated under radio frequency (RF). Their response to different RF fields were measured as well as the AuNP+Neuron interaction upon RF exposure. Thermal effects were observed during RF exposure and after the source was turned off. This shows that the particles act as a thermal source, which can be beneficial in cancer therapy. This dissertation focuses on a novel synthesis technique of biocompatible gold nanoparticles and measures the combinatorial effects upon stimulation with various portions of the electromagnetic spectrum.


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Chitosan, Electromagnetic Spectrum, Functional Nanoparticles, Neuron stimulation



Physics and Astronomy