Determination of biophysical and chemical properties of short-chain molecules and biological nanoparticles

Knowledge of physical and chemical properties such as size, diffusivity, concentration and stability of an analyte in a sample is critical in science and engineering. When working in a small size range (0.1-100 nm), which includes short-chain molecules (e.g., ethanol) and nanoparticles, the number of methods that can be used for their characterization becomes sparse and each one has its limitation such as accuracy, resolution, cost of instrumentation and time needed for sample preparation and analysis which introduces more complexity to the problem being solved. This became the motivation and focus of the presented work. The goal of the conducted research was to explore the available methods as well as develop new methods that can be used for characterization of different analytes. The first half of the dissertation introduces the use of interfacial tension for estimating stability of nanobubbles that can be applied as contrast agents for ultrasound imaging or as vehicles for drug delivery. Use of interfacial tension is then shown to be applicable in a new setup and conditions to determine the diffusion coefficient and concentration of an analyte in any given location. Adsorption of perfluorocarbon vapor to the water surface is then explored. The second half of the dissertation focuses on characterization of endogenous nanovesicles called exosomes. This section continues the first section by presenting a novel finding of surface activity of exosomes which provides a potential mechanism of their adsorption to the cell membrane as well as application of dynamic interfacial tension for measuring exosome concentration in a sample. This section continues by comparing techniques that were previously used by others to determine size and shape of exosomes but were not compared to each other either due to unavailability of instrumentation or focus of the study being unrelated to size and shape. This study not only allowed examining the advantages and disadvantages of each technique but also lead to new findings about the biophysical properties of exosomes. This section ends with an application of quartz crystal microbalance method for measuring average mass and concentration of exosomes in a sample.