Summary of dissertation research

The goal of my dissertation research was to evaluate how nanomaterial physical and chemical properties influence toxicity toward biological systems such as bacteria and plants. The specific aims of my research were to:

1. determine the bactericidal efficacy of NO-releasing silica, dendrimer, and chitosan scaffolds against planktonic and biofilm bacteria as a function of size, shape, and surface exterior functionality;

2. evaluate the mechanisms of antibacterial activity for these scaffolds using confocal microscopy; and,

3. determine the phytotoxicity and uptake of silica nanoparticles for Arabidopsis thaliana as a function of the physical properties of this scaffold.

In this introductory chapter, the potential of NO-releasing silica, dendrimer, and chitosan scaffolds are justified for antibacterial applications. The physicochemical properties of these NO-release vehicles are critical for tuning the influence of nanomaterial–cell interactions and drug (i.e., NO) delivery efficiency. Likewise, these properties prove important in dictating nanoparticle toxicity to plants. In order to develop safe nanomaterials with minimal risk, we must examine how they act in the body and on the environment. In Chapter 2, planktonic bacterial killing with NO using three distinct sizes and shapes of silica nanoparticles, dendrimers with varied exterior functionalities, and chitosans of different molecular weights and hydrophobicities is described. Subsequent studies in Chapter 3 utilize these NO-releasing scaffolds to evaluate the eradication of more clinically-relevant bacterial biofilms as a function of nanomaterial size, shape, exterior functionality, and molecular weight. In Chapter 4, NO-releasing dendrimers with identical NO storage but varied NO-release kinetics are used to evaluate the desired NO-release profiles for killing of planktonic and biofilm bacteria. The

importance of size and shape on silica nanoparticle phytotoxicity to Arabidopsis thaliana is described in Chapter 5. Finally, Chapter 6 provides an overall summary of my dissertation work and details possible future directions in evaluating nanomaterial physicochemical properties and their relation to potential toxicity.

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