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Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers
Published on: October 17, 2013
KINETICS OF PENETRATION : VII. MOLECULAR VERSUS IONIC TRANSPORT.
W J Osterhout1, S E Kamerling, W M Stanley
1Laboratories of The Rockefeller Institute for Medical Research.
The Journal of General Physiology
|October 30, 2009
Summary
Cell electrolyte penetration order mimics water mobility but occurs mainly as molecules. Partition coefficients, not ionic mobilities, primarily drive this cation transport across membranes.
Area of Science:
- Biophysics
- Cell Biology
- Physical Chemistry
Background:
- The order of cation penetration into cells often correlates with their ionic mobilities in water.
- This observation has suggested that electrolytes primarily cross cell membranes as ions.
Purpose of the Study:
- To investigate the mechanism of cation penetration across a non-aqueous layer representing the protoplasmic surface.
- To determine whether ionic mobility or other factors govern the observed penetration order.
Main Methods:
- Utilized model systems with a non-aqueous layer between two aqueous phases to simulate cell membranes.
- Analyzed cation penetration order and correlated it with partition coefficients and molecular mobilities.
Main Results:
- Cation penetration order (Cs > Rb > K > Na > Li) matched water ionic mobilities but occurred predominantly in molecular form.
- Partition coefficients were identified as the primary drivers of penetration rate, dictating the concentration gradient.
- Molecular mobilities within the non-aqueous layer showed little variation, and ionic contributions were deemed negligible.
Conclusions:
- Electrolyte penetration across cell membranes is largely molecular, not ionic, despite apparent correlations with ionic mobility.
- Partition coefficients are the key determinant of cation entry rates, overriding ionic mobility in non-aqueous environments.
- The findings provide a new model for understanding ion transport across biological membranes, applicable to living cells.
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