Synthesis and polymerization of bicontinuous cubic nanoparticles from reactive amphiphiles

Abstract

Amphiphiles are composed of a polar, hydrophilic headgroup and one or more non-polar, hydrophobic tail(s). Hydrated amphiphiles self-organize to form various liquid crystal phases as a function of molecular structure, temperature, concentration, and pressure. Self-supported arrays of self-organized, hydrated amphiphile assemblies include lamellar/vesicles, various normal (Q I) and inverted (QII) cubic phases, and normal (HI) and inverted (HII) hexagonal phases. A bicontinuous cubic liquid crystalline lipid-water phase is one in which the lipid bilayers are arranged in periodic three-dimensional cubic lattice structures. Cubic liquid crystalline nanoparticles prepared from aqueous dispersions of cubic lipid-water phases are kinetically stable in the presence of certain dispersing agents. The ability to incorporate and deliver lipophilic, amphiphilic, and water-soluble molecules in a controlled manner and great biocompatibility of cubic nanoparticles make them excellent candidates for drug delivery applications. Stabilization of the cubic nanoparticles has been achieved through polymerization of the reactive lipids in cubic lipid assemblies. Several QII-forming amphiphiles have been designed and synthesized. Certain compositions of these amphiphiles and water plus cross-linking monomers yield bicontinuous cubic phases, which can be dispersed into cubic nanoparticles in water using Poloxamer 407. These cubic nanoparticles were studied by 2H NMR, Transmission Electron Microscopy, and Scanning Electron Microscopy. The polymerization of the hydrated amphiphiles in the lipid region successfully stabilized the cubic nanoparticles. Selective and simultaneous polymerizations of the reactive groups in regions of different polarity within an inverted bicontinuous cubic phase were achieved via appropriate choice of initiation chemistry. The ability to form stable biocompatible nanoparticles with interpenetrating water channels of high internal surface area provides opportunities for the sequestration and release of relatively large molecules from these novel nanoparticles. Organic light-emitting diodes (LEDs) have attracted much attention because of their academic interests and potential utility of this technology in a wide variety of applications. A more efficient electroluminescent (EL) device requires balanced charge injection and transport of both electrons and holes. Discotic liquid crystalline LEDs are very effective as charge transport and energy transfer conduits, due to the high degree of electron communication between mesogen cores within the columnar packing. Phthalocyanines are well known to form columnar discotic liquid-crystalline mesophases. A novel oxadiazole substituted liquid crystalline phthalocyanine containing hole-transport phthalocyanine moiety as the core and electron-transport oxadiazole moieties on the periphery was designed and synthesized.