Unilamellar liposomes covalently coupled on silica gel for liquid chromatography

Abstract

Silica gel was used as a support for the covalent coupling of liposomes, which could overcome drawbacks of soft gel beads in column efficiency and separation speed. The influences of the concentration of added dimethylaminopyridine and reaction time on the chloroformate activation reaction of silica gel were investigated. Temperature and pH for covalent coupling of liposomes on the activated silica gel were also optimized. Experimental results indicated that the stability of the covalently coupled liposome columns was obviously superior to that of the noncovalently coated liposome columns but the selectivity of both columns was basically identical. Separation and analysis of a crude extract of a traditional Chinese medicine Ligusticum Wallichii and a mixture of small peptides on both columns further support this conclusion.

Separation of compounds interacting with liposome membrane in combined prescription of traditional Chinese medicines with immobilized liposome chromatography

“…Preparations of the immobilized liposome columns have been reported elsewhere [23,24]. Briefly, PC (0.1-1 g) was dissolved in chloroform and 2-16 g silica gel was added to the solution, shaken for 30 min, and the solvent was removed in a round-bottomed flask by rotary evaporation, and then the dried silica was kept under high vacuum overnight to remove the remaining solvent.…”

Strategy for analysis and screening of bioactive compounds in traditional Chinese medicines

“…Reversed-phase high performance liquid chromatography (RP-HPLC) can be a tool to model solute-membrane partitioning, but it only primarily model the hydrophobicity interaction between solutes and membrane whereas the interactions between solutes and the polar lipid head groups of membrane are not well included, which is also believed to be important for the partition of drugs to biological membranes. A novel chromatography method, immobilized biomembrane chromatography (IBMC), has also been developed recently as a powerful model to study drug-membrane interactions in vitro [54,55]. It can be subdivided into cell membrane chromatography (CMC) and immobilized liposome chromatography (ILC).…”

“…However, soft gel beads such as sepharoses and sephadexes that were still the main supports of liposome immobilization in liquid chromatography research presently impeded further development of the technique because they all suffer from some drawbacks, such as large particle size, wide size distribution and poor mechanical strength that resulted in the low column efficiency and low separation speed. For effectively avoiding these drawbacks above, Mao et al [57] proposed a covalent coupling method for preparing the covalently immobilized unilamellar liposome stationary phase on porous silica. Experimental results indicated that the stability of covalently coupled liposome column was obviously superior to that of coated liposome column but the selectivity of both columns was basically identical.…”

“…So the permeability of drugs across intestine has been considered as one of most important coefficients to evaluate their bioactivity. Because biomembrane chromatography with the immobilizing liposome as stationary phase could closely mimic the interaction of analytes with biological membranes including intestine epithelial cells, it can be used as a tool for prediction of drugs absorption in intestine [55]. Mao et al [59] found the weighed retention value of drugs under three pH on the immobilized liposome chromatography existed good correlation with their cell absorption rate constants P app .…”

“…Because biomembrane chromatography with the immobilizing liposome as stationary phase could closely mimic the interaction of analytes with biological membranes including intestine epithelial cells, it can be used as a tool for prediction of drugs absorption in intestine [55]. Mao et al [59] found the weighed retention value of drugs under three pH on the immobilized liposome chromatography existed good correlation with their cell absorption rate constants P app . Therefore, biomembrane chromatography can be applied as a model in vitro to study absorption and distribution of active components from TCMs in human body.…”