Some considerations concerning the technical use of narrow pores

Carrier transport and diffusion through narrow pores (single-file diffusion) are basic transport mechanisms that have been proposed to explain the specific passive permeation properties of biological membranes. Unlike carrier diffusion, the concept of single-file diffusion has been scarcely considered in connection with technical purposes. Taking into account, however, that extensive studies have been made in recent years on artificial lipid membranes with single-file pores and that cylindrical pores with a very narrow diameter distribution can be produced in thin plates by etching nuclear tracks, it seems useful to discuss more carefully the specific properties and conceivable applications of the single-file pore. As properties of obvious technical interest one finds high permselectivity and high transport rate. In addition, the voltage-dependent block of narrow pores provides an intriguing possibility of ionic flux control. A therapeutic system functioning as an artificial suprarenal gland is briefly outlined as an example.