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Abstract:
The interactions of the local anesthetic Dibucaine with some lipid monolayers were studied at the air/water interface by measuring the surface pressure-area and the surface potential-area isotherms at different pH values of 4, 7 and 10 respectively. At any given pH, there was large expansion of film area at low surface pressure for negatively charged phospholipids. This expansion could be interpreted as a preferential binding of this drug to anionic phospholipids. The surface potential value of the lipid monolayers spread on the subphase containing Dibucaine showed a significant decrease with increasing pH. This indicated a depolarization effect of the Dibucaine on the lipid monolayers at high pH. The uptake of the anesthetic molecule by the various lipid monolayers was also studied by measuring the absorption spectra of these monolayers transferred onto quartz with the anesthetic bound to the monolayers. The results obtained have been discussed in terms of the neutral and charged forms of Dibucaine and the interactions of these various forms with the lipid monolayers. Results indicate that the charged form interacts more strongly with the lipids than does the neutral species.
