Study of Solute Partitioning in Biomembrane−Mimetic Pseudophases by Electrokinetic Chromatography:  Dihexadecyl Phosphate Small Unilamellar Vesicles

Abstract

Solute partitioning into vesicles of dihexadecyl hydrogen phosphate (DHP) was investigated by electrokinetic chromatography (EKC). The ionic double-chain surfactant forms bilayer structures that mimic a biological membrane when dispersed in aqueous media. The linear solvation energy relationship (LSER) was used to gain insights about the nature of interactions and parameters that influence the partitioning process into vesicles, micelles, and n-octanol. The Gibbs free energies of transfer of selected functional groups from aqueous to vesicular phases were compared to those in micellar pseudophases of sodium dodecyl sulfate (SDS) and sodium dodecyl phosphate (SDP). Size and hydrogen bond acceptor strength of solutes are the main factors that determine their partitioning behavior, while dipolarity and polarizability play minor, yet significant, roles. It was determined that the cohesiveness of solute microenvironments in DHP vesicles is between those for micells and n-octanol. Vesicles are weaker hydrogen bond donors and less dipolar than micelles; however, they interact more strongly with the n and π electrons of solutes. Interestingly, as the organization of the pseudophase is enhanced from micelles to vesicles, their microenvironments become closer to that of octanol. Consequently, solute partitioning in vesicle−water correlates better with that in octanol−water than with that in micelle−water. The influence of the presence of cholesterol in the bilayer on the interactive nature of the pseudophase was also investigated.

Determination of Vesicle–Water Partition Coefficients by Electrokinetic Chromatography: Study of Temperature Effect

“…The LSER models provide information about the contributions of hydrophobic, hydrogen bonding, dipolar, and polarizability interactions to solute partitioning into vesicles. Using the recently revised notations (10), the LSER model for vesicle-water partition coefficient, K vw , or retention factor, k, can be written as log(K vw or k) = vV + bB + aA + sS + eE + C, [4] where V, B, A, S, and E represent the solutes' descriptors for volume, hydrogen bond acceptor strength, hydrogen bond donor strength, dipolarity, and polarizability, respectively. The coefficients v, b, a, s, and e represent the interactive of solvation properties of the pseudo-phase.…”

“…As suggested earlier (and shown in Eq. [4]), using either partition coefficient or retention factor in the LSER model should provide the same solvation information about a given pseudo-phase (4,12). For example, in a prior study, we reported the LSER models of retention factor in vesicular electrokinetic chromatography (VEKC) for DHP and DHP/Chol pseudo-phases.…”

Quantitative Retention‐Activity Relationship Studies by Liposome Electrokinetic Chromatography to Predict Skin Permeability

“…[21][22][23][24][25][26][27][28][29][30][31][32] In this technique, liposome was added to the electrophoretic buffers. The liposomes act as a pseudo stationary phase where solutes are separated according to their differences in electrophoretic mobilities and in liposome-water partitioning.…”

Selectivity of single, mixed, and modified pseudostationary phases in electrokinetic chromatography

“…Polymers and copolymers constitute the main source, and offer a wide range of possibilities [7][8][9][10]. Nowadays other types of compounds, like liposomes, have been proposed as pseudostationary phases [11][12][13]. These new systems, together with the most typical phases, generate a very large number of pseudostationary phases with different selectivities.…”

“…They have studied the effect of the surfactant counter-ion [23], and polar head group [24,25] on the solvation coefficients of SDS-based surfactants. Moreover, they have also characterized some liposomial systems [11,12,26]. Palmer and coworkers [7,9,27] have developed, characterized, and compared a great number of polymeric pseudostationary phases.…”