Construction And Phase Transition Of Drug-loaded Liquid Crystals

Surfactant molecules can self-assemble into a large variety of morphologies, including liquid crystal, microemulsion and micelle. Lyotropic liquid crystal has long range order and short-range disorderly morphology on the microstructure, it is widely exists in the cell membrane of the organism with good biocompatibility. In recent years, lyotropic liquid crystal has attracted more and more interest of researchers due to its potential in excellent drug release properties. In this paper, by considering the application perspective of lyotropic liquid crystal in drug carrier, biocompatible surfactant is chosen to construct liquid crystal. We have studied that the change of the component and the temperature induce the transition of the lyotropic liquid crystal by using the rheological method. Furthermore, the application of the lyotropic liquid crystals used as a carrier of drugs combining with the result of rheological experiments, including the release behavior and light stability of curcumin was studied, respectively. This paper mainly includes the following four chapters: 1. InstructionOn the basis of consulting a large number of domestic and foreign literatures, the current state of research and the application progress about lyotropic liquid crystal as drug delivery are expounded systematically. Through the above literature review, it is found that lyotropic liquid crystal as a drug carrier has the advantages of pharmaceuticals. Both the hydrophilic drug and the lipophilic drug may be solubilized into the liquid crystals better because of its special structure. Moreover, liquid crystal has good protection on the unstable drug and control drug release rate. The research of phase transition can be a guide for us to study in vitro release properties. So we have studied that the composition and temperature induce lyotropic liquid crystal phase transition, and combined with drug release properties of the research in our work. 2. The construction of liquid crystals encapsulating drug and component induced phase transition of liquid crystalThis study constructed new curcumin-loaded lyotropic liquid crystals containing pharmaceutically accepted oil, ethyl oleate(Et OL). Three liquid crystalline phases including lamellar, hexagonal and cubic phases were identified by means of the polarized optical microscopy and rheology method. By analyzing the low shear viscosity, the viscosity of curcumin-liquid crystals is smaller than those without curcumin. Dynamic rheological results show that: Dissolved curcumin in EtOL can make the elastic modulus of hexagonal and cubic phase increase compared with that without curcumin, while the elastic modulus of lamellar phase decreases. Dissolved curcumin in Brij 97 can lead to the decreasing of the elastic modulus for cubic and lamellar phases, whereas it has little influence on hexagonal phase. When the curcumin is solubilized in both EtOL and Brij 97, the elastic modus of hexagonal phase increase, the elastic modus of lamellar and cubic phases decrease compared with that without curcumin.3. Temperature induced transitions in lyotropic liquid crystalsThis chapter mainly based on the rheological properties of liquid crystal under different temperature and discusses the temperature induced the transition of hexagonal phase, cubic phase, lamellar phase liquid crystals.(1) The dynamic moduli of hexagonal phase decrease with the increase of temperature, which suggests that at low temperature hexagonal crystal structure is more stable. In the studying temperature range, hexagonal phase shows three turning points, reflecting that the curcumin-hexagonal phase undergoes an order-to-disorder process with increase in temperature. When the temperature increases to 52oC, the hexagonal phase is destroyed and turns to micelle. The higher transition temperature is advantageous to the storage of curcumin-hexagonal liquid crystal at room temperature. The viscosity of the hexagonal liquid crystal decreases with the increase of temperature, which can be fitted by an Arrhenius equation at low shear rate.(2) The rising of temperature result in the decreasing of dynamic modulus and viscosity. Three phase transition areas are also found in the temperature range. When the temperature increases to 37oC, cubic phase liquid crystal transforms into the micellar solution. The phase transition temperature is close to the human body temperature, so it is a potential application value to study drug release for cubic phase. Lamellar phase liquid at high temperature(60oC) can still maintain a relatively stable layered structure 4. The drug in vitro release and stability in lyotropic liquid crystalThe drug release properties of lyotropic liquid crystal with different oil content at different temperature and the light stability in different pH media are studied in this chapter. The release rate of the hexagonal phase and cubic phase liquid crystal encapsulating curcumin is markedly lower than that of curcumin ethanol solution which behaves good sustained release effect. The drug release behavior of hexagonal and cubic phase encapsulating curcumin can be fitted by the first-order kinetic equation, the correlation coefficient is not lower than 96%. Through the light stability study, it is found that the stability of curcumin in neutral medium of liquid crystal is better, the more alkaline is unstable.