Preparation and characterization of aqueous nanoparticles from molecular and macromolecular amphiphiles.

摘要

Colloidal nanoparticles are particles with sizes ranging from one nanometer to several hundred nanometers, which disperse evenly in a dispersion medium. In aqueous solutions, amphiphilic molecules organize themselves to form such colloidal systems so that the hydrophobic chain segments are removed from the aqueous environment in order to achieve a state of minimum free energy. In this dissertation, molecular and macromolecular amphiphiles that form two types of colloidal nanoparticles were synthesized. The assemblies formed by these amphiphiles in aqueous solution were characterized and investigated as potential carriers for smaller particles and molecules.;In the first study, diacetylenic lipids were synthesized by optimizing a literature method or via new synthetic routes. Studies were focused on preparing polydiacetylenic liposomes as carriers for small particles. In a model study, dextran-coated superparamagnetic iron oxide nanoparticles were loaded inside the liposomes. The relative loading density inside liposomes and the percentage of iron oxide incorporated were investigated among liposome systems with different feeding ratios of iron oxide to total lipids. Biotinylated lipids were incorporated into liposome formulations to probe the surface biotin group availability; however, the measured biotin surface presence was lower than expected.;To make the second type of colloidal particles, a series of triblock copolymers, poly(ethylene oxide)-b-poly(ethylene oxide- stat-butylene oxide)-b-poly(isoprene), were prepared via sequential anionic ring-opening polymerization and nitroxide-mediated radical polymerization. The polymer aggregates formed at room temperature had relatively narrow size distributions and near-spherical shapes. The relative aggregate sizes appeared to be dictated by the length of the isoprene block when the lengths of the other two blocks were fixed. Most of these polymers exhibited a significant size expansion in their aggregate structures when the polymer solution was heated to a high temperature, as evidenced by DLS and TEM studies. The structural transition between large and small aggregates was simply controlled by temperature variation. An initial encapsulation study showed successful loading of iron oxide particles with hydrophobic coatings inside the polymer aggregates.