RESUMO
Artificial supramolecular-hierarchical structures that emulate nature represent an overcoming alternative for the design of new drug delivery systems. Thermodynamic and topographic properties of films formed by a monoacylated amphiphilic ß-cyclodextrin (ßCD-C16) with the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at the air/water interface were studied. ßCD-C16 formed stable mixed films with POPC at several proportions when spread together at the air/water interface. The orientation of ßCD-C16 cavity at the interface depends on its mole fraction in the film as reveled by the analysis of partial mean molecular areas as a function of composition. Furthermore, ßCD-C16 was able to penetrate POPC preformed films in a broad range of initial surface pressures, including that near the collapse pressure of the phospholipid. These results demonstrated the strong tendency of ßCD-C16 to be inserted into this lipid matrix commonly used in liposome formulations. Topography studies show that ßCD-C16 segregate from POPC forming clusters enriched in ßCD-C16. Segregation of ßCD-C16 was especially noticeable when ßCD-C16 were incorporated by themselves into a preformed POPC matrix leading to ordered and highly birefringent structures that suggest the formation of hierarchical stacked ßCD-C16 arrangement at the interface.