Interaction of a dental filling material eluate and membrane lipids

The possibility that 4-N,N-dimethyl amino benzoic acid ethylester (DMABEE), a leachable lipophilic component of dental fillings, could interact with biological membranes was investigated. Interaction of DMABEE with phospholipids was studied by two methods: First, by determining the surface pressure/molecular area isotherms at 37degrees C of glycerophospholipids monolayers, using the Langmuir technique: and second, by phase transition parameters in liposomes of the same lipids, using differential scanning calorimetry (DSC). DMABEE clearly interacted, in a concentration-independent manner, with monolayers of saturated phosphatidylcholines (PC, i.e., markers of the outer membrane leaflet) and phosphatidylserines (PS, i.e., markers of the inner membrane leaflet). This interaction increased with increasing acyl length in the lipids and was greater with PC than with PS. These observations with monolayers were confirmed by the studies of liposomes of PC and PS.