Liposome Electrokinetic Chromatography And Its Application In Profiling Drug Membrane Transport

Half of the funds were consumed in clinical studies in development of new medicine, so the estimation of the properties of drug-like compounds was important before clinical studies. The throughput of the lipophilicity which governs a drug delivery to the target site and activity should proceed before the research of activity, or simultaneously. Liposome electrokinetic chromatography (LEKC) is one of the tools which are used to evaluate the lipophilicity of the compounds. This technique utilizes the same instrumental setup as capillary electrophoresis, but in this case liposomes are in the buffer solutions. The liposomes act as a pseudostationary phase and provide partitioning sites for solutes. The dissertation was put emphasis on the basic research of LEKC, and the retention of drugs in LEKC(logk_LEKC) was related with its pharmacologic/pharmacokinetic activities by chemometrics. The quantitative retention-activity relationships were built and it would provide a new technical platform to evaluate the activities of drug candidates.The liposomes were prepared with egg phospholipid(PC) and phosphatidylserine (PS) of high purity. The reproducibility and stability of LEKC were good. The anionic phospholipid content of the liposomes has infulence on the interactions between liposomes and charged drugs. The additions of HPC and cholesterol to the liposomes will decrease the retention of drug in LEKC by influencing the rigidity of phospholipid membrane. The decrease of charged drugs partitioning in liposmes with increase of ionic strength of buffers is due to the shielding of the charge on the liposomes surface in addition ot the shielding of the charge on the drug molecule by the buffer counter ions, thus decreasing the electrostatic interactions. An increase in pH results in a smaller degree of ionization of the basic drugs and consequently leads to a lower degree of interaction with the negatively charged membranes, on the other hand, an increase in pH results in a larger degree of ionization of the acidic drugs and consequently leads to a larger degree of interaction with the negatively charged membranes. Linear salvation energy relationship(LSER) model was used to characterize the contributions from various types of interactions for solute partitioning into liposomes. Size and hydrogen bond acceptor strength of solutes are the main factors that determine partitioning into bilayers. LSER models show that increasing amounts of cholesterol in the lipid phase decreases the hydrogen bond acceptor ability.The lipophilicity of LEKC is very different with IAM and n-octanol/water system. The lipophilicity of thirteen physicochemical models and five biological activity models was compared by the distance vector method and principal component analysis(PCA), the results indicated that LEKC was similar with VEKC in lipopholicity. LEKC and n-octanol/water system was similar in lipophilicty as the test solutes were neutral compounds, this suggested logP of neutral compounds could be obtained by indirect measurement. Only the skin permeability coefficients model of five biological activity models was close to LEKC model.The predictive model was constructed by LEKC using twenty-seven neutral compounds, and the predictive ability of the model was validated using other thirteen compounds. The sigamoidal relationship was seen by correlating the drug fraction absorbed in human (Abs%) with logk_LEKC, the outliers were the drugs which were transported by non-transcellular pathway. The results of PCA method showed that logk_LEKC was more similar to logBB than logk_VEKC, PSA, logP and logD7.4. A quantitative retention-activity relationship was development to predict skin permeability coefficients form three solute descriptors: logk_LEKC, molecular weight and the count of -OH and -NH in the solute structure. The model was generated using 22 structurally diverse compounds and validated using the same set of compounds by the leave-one-out approach.