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Thesis (Ph.D.)--Lehigh University, 2009. / Advisers: Mohamed S. El-Aasser; E. David Sudol.

New kinds of reactive catanionic vesicles were formed and their physical and chemical properties were studied. All ion-paired amphiphiles studied formed vesicular aggregates of over 100 nm in diameter as determined by differential scanning calorimetry and quasielastic light scattering. This is the first report on cross-linked ion-paired amphiphiles containing heterobifunctional fatty acid components. The reaction of heterobifunctional fatty acids produced, depending on the type of initiator, different polymers. Redox initiation produced cross-linked polymers and hydrogen peroxide produced linear-ladder-like polymers. These polymerized structures were analyzed by UV and NMR spectroscopy, vesicle dissolution experiments, and solubility experiments. The polymerization of some reactive catanionic vesicles gave information on the competition between 1,4 and 3,4-addition of monomers. These polymerized structures are a new class of compounds with promising properties. A new form of polymerizable reactive ester was synthesized in conjunction with different types of polymerizable phospholipids and their behavior at the air-water interface and ability to form Langmuir-Blodgett type films was tested.

Liquid crystals possess both order and mobility. Hydrated, natural and synthetic amphiphiles self-organize to form various liquid crystal phases as a function of molecular structure, temperature, concentration, and pressure. Self-organization is the ordering of molecules via non-covalent interactions, i.e. hydrogen bonding, van der Waals, pi-pi interactions, ionic interactions, hydrophobic short-range forces, and London dispersion forces. Amphiphiles contain both polar and non-polar moieties. In general, amphiphiles are composed of a polar, hydrophilic headgroup and one or more non-polar, hydrophobic tail(s). At equilibrium, the unfavorable enthalpic interaction of the polar water molecules with the non-polar amphiphile tails is minimized by the aggregation of the latter with the non-polar tails of other amphiphiles to form a water excluded hydrophobic block, while the hydrophilic headgroups line the interface of the phase-separated aqueous domains. Self-supported arrays of self-organized, hydrated amphiphile assemblies include lamellar/vesicles, various normal and inverted cubic phases, and normal and inverted hexagonal phases. The inverted hexagonal (HII) phase can be considered as aqueous columns patterned in a hexagonal fashion. The polar amphiphile headgroups are well ordered at the water-amphiphile interface, while their non-polar tails are disordered and fill the area between the aqueous water channels. In general, amphiphiles with two or more non-polar chains and a small, poorly hydrated headgroup favor the formation of the HII phase. Longer tails or the incorporation of bulky design elements, i.e. cis-double bonds or branching substituents, in the amphiphile tail(s) lowers the temperature associated with the formation of the HII phase. Several HII-forming amphiphiles have been designed and synthesized. Upon hydration, the phase behavior of these amphiphiles was evaluated by 31P-NMR assembly characterization. Radical polymerizations were used to stabilize the HII phase assemblies resulting in cross-linked polymer networks. The cross-linked materials displayed dramatically different physical properties, i.e. lowered solubility in common organic solvents. The polymer assembly phase behavior was evaluated via 31P-NMR after polymerization. A synthetic route to phosphoethanolamines via a novel di-protected glycerophosphoethanolamine has been designed and developed. A phosphoethanolamine lipid has been synthesized using this route. The route appears to be general to the synthesis of any phosphoethanolamine.

The use of liposomes for the delivery of therapeutic agents to tumor sites took a major step forward with the introduction of sterically stabilized liposomes (PEG-liposomes). Several research groups reported the increased localization of PEG-liposomes at tumor sites. Once PEG-liposomes reach these sites, it can be desirable to increase the rate of release of encapsulated compound(s). The use of radiation for this purpose is attractive, because it can be delivered in a spatially and temporally selective manner. An effective strategy for the photopertubation of PEG-liposomes relies on the photoinitiated polymerization of reactive lipids in the liposomal bilayer. Previous studies indicated that the inclusion of the photoreactive 1,2-bis[10-(2' ,4'-hexadienoyloxy)decanonyl]-sn-glycero-3-phosphocholine (bis-SorbPC17,17) among the lipids of PEG-liposomes had little effect on their permeability until the PEG-liposomes were exposed to UV light. Photoexposure increased the permeability of the PEG-liposomes 200-fold. Research in this dissertation was focused upon increasing the reactivity of PEG-liposomes to UV and ionizing radiations. Additionally, the most favorable formulations were then used for the encapsulation of chemotherapeutic compounds that are currently on the market. Results in this dissertation indicate the ability to encapsulate water soluble compounds with high efficiency and subsequently release those compounds with minimal UV light exposure and with ionizing radiation doses that approach therapeutic levels.