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Interfacial interaction between dextran sulfate and lipid monolayers: an electrochemical study
Hélder A Santos1, Vladimir García-Morales, Robbert-Jan Roozeman
1Department of Chemical Technology, Laboratory of Physical Chemistry and Electrochemistry, Helsinki University of Technology, P.O. Box 6100, FIN-02015 HUT, Finland.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 1, 2005
Summary
Dextran sulfate interacts with lipid monolayers, forming condensed layers. Calcium ions facilitate binding, influencing drug transfer across these layers, with results confirmed by spectroscopy.
Area of Science:
- Biophysics
- Surface Chemistry
- Electrochemistry
Background:
- Lipid monolayers are crucial in biological membranes.
- Dextran sulfate (DS) is a charged polymer with potential biological interactions.
- Understanding DS-DPPC and DS-DPPA interactions is key for biomaterial design.
Purpose of the Study:
- To investigate the interaction between dextran sulfate and dipalmitoylphosphatidylcholine/dipalmitoylphosphatidic acid monolayers.
- To elucidate the mechanism of DS adsorption on lipid monolayers.
- To study the effect of DS on the transfer of a cationic drug across lipid monolayers.
Main Methods:
- Langmuir-Blodgett (LB) technique for monolayer formation and transfer.
- Electrochemical methods (AC voltammetry, cyclic voltammetry) for monitoring ion and drug transfer.
- Compression isotherms and capacitance-potential measurements.
- Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) for structural analysis.
Main Results:
- Dextran sulfate forms a more condensed hybrid layer with DPPC and DPPA, suppressing DPPC phase transitions.
- Calcium ions mediate DS binding to lipid monolayers, enhanced at lower surface pressures.
- Drug (metoprolol) transfer across lipid monolayers is significantly influenced by surface pressure, applied potential, and phospholipid charge.
Conclusions:
- DS adsorption on lipid monolayers is mediated by calcium ions and electrostatic attraction.
- The resulting hybrid lipid layers modulate the permeability for charged molecules.
- Surface pressure and applied potential are critical parameters controlling DS-lipid interactions and drug transport.