Hexaarylbiimidazoles(HABI)-functionalized lyotropic liquid crystalline systems as visible light-responsive materials.

Hexaarylbiimidazoles (HABIs) are a promising class of photoswitchable molecule that have received little attention in the literature. Among them, (2,2'-dimethoxydiphenylimidazole)-1,1'-binaphthyl (HABI1) displays unusual negative photochromism and is responsive to green light. This study investigates the potential of HABIs to serve as photo-responsive actuators controlling the structure of lyotropic liquid crystalline (LLC) materials. HABI1 with four methyl chains and HABI2 with four dodecyl chains were synthesized. Time resolved small angle X-ray scattering was used to characterize the potential disruptive effects of HABIs on the nanostructure of LLC systems. HABIs underwent rapid isomerization under irradiation, with a very slow reversion in the dark in toluene and in the LLC matrix, demonstrating excellent stability and photo-fatigue resistant. HABIs completely triggered phase transitions in the phytantriol-based materials, and HABI2 generated a greater disruption than HABI1 on the lipid packing due to the enhanced steric influence. Tuning the lipid composition yielded systems that transitioned from a "slow release" lamellar phase to a "burst release" bicontinuous cubic phase upon light irradiation. Such systems therefore may exhibit a triggered release behavior upon a short time of irradiation, showing great potential in "on demand" drug delivery.

Visible light-triggered cargo release from donor acceptor Stenhouse adduct (DASA)-doped lyotropic liquid crystalline nanoparticles.

Light-responsive nanocarriers are applicable as non-invasive, highly tunable and precisely controlled drug delivery systems. Here, we report a new nanocarrier system, achieved by doping D1, a type of green light-responsive donor acceptor Stenhouse adduct (DASA), into a lipid-based lyotropic liquid crystalline system. Time-resolved small angle X-ray scattering was used to confirm that the matrix underwent a rapid and fully reversible phase transition from lamellar to inverse cubic phase upon irradiation with green light (532 nm), reverting back on removal of light. Fluorescein isothiocyanate-dextran (FD4) was used as a model hydrophilic cargo. The release of cargo upon varying irradiation parameters was investigated in vitro which showed that irradiation can trigger a burst release of FD4 upon phase transition. This additive shows promise for the development of new visible light-activated, "on demand" drug delivery systems.

Investigation of Donor-Acceptor Stenhouse Adducts as New Visible Wavelength-Responsive Switching Elements for Lipid-Based Liquid Crystalline Systems.

The ability of donor-acceptor Stenhouse adducts (DASAs) to function as a green light responsive switch for lipid-based liquid crystalline drug delivery systems was investigated. The host matrix comprising phytantriol cubic phase was selected due to its high sensitivity toward changes in lipid packing. Small-angle X-ray scattering demonstrated that the matrix undergoes rapid and fully reversible order-order phase transitions upon irradiation with 532 nm light, converting between the bicontinuous cubic phase and reversed hexagonal phases. This approach shows promise for use as an actuator for the development of visible wavelength light-activated, "on-demand" drug delivery systems.