Transport of organic ions through lipid bilayers

Abstract

The transport of a series of charged drugs and other organic ions through lipid bilayers was studied, using single-bilayer liposomes. Monovalent organic cations and organic anions could carry charge into the liposomes independent of the nature of their counter ion. Ion-pair formation, following the addition of an excess of I- or Br-, did not facilitate this transport. However the passage of organic cations and anions across the membrane required the presence of the organic anion tetraphenylborate in the lipid bilayer. This effect of tetraphenylborate is probably due to a lowering of an intra-membrane potential energy hill, the principal barrier for transport, and not to ion-pair formation. It is concluded that organic ions that possess sufficiently lipophilic structures to mask their charged character, can pass lipid bilayers in charged form.

Ion-pair Formation as a Strategy to Enhance Topical Delivery of Salicylic Acid

“…Although the relevance of ion-pair formation to the membrane uptake of ionised molecules has been discussed, very little systematic study has been attempted (Ruifrok & Meijer 1981) to examine how and why ion pairs could be employed in this role. The formation of ion pairs between ions of opposite electrical charge is both solute and environment dependent (Tomlinson et al 1982).…”

Effect of Ion Pairing with Alkylamines on the In-vitro Dermal Penetration and Local Tissue Disposition of Salicylates

“…Although the relevance of ion-pair formation to the membrane uptake of ionised molecules has been often discussed, there are very few systematic studies (Ruifrok & Meijer 1981) to examine how and why ion pairs could be employed in this role. A variety of amines have been reported as topical formulatory adjuvants (Poulsen et al 1968;Quack 1976).…”