Host-guest interactions between cyclodextrins and surfactants with functional groups at the end of the hydrophobic tail

Abstract

Graphical abstractIn this work the influence of the incorporation of aromatic substituents at the end of the hydrophobic tail on the binding of cationic surfactants to cyclodextrins was studied. 2 HOST-GUEST INTERACTIONS BETWEEN CYCLODEXTRINS AND SURFACTANTS WITH FUNCTIONAL GROUPS AT THE END AbstractThe aim of this work was to investigate the influence of the incorporation of substituents at the end of the hydrophobic tail on the binding of cationic surfactants to α-, β-, and -cyclodextrins. The equilibrium binding constants of the 1:1 inclusion complexes formed follow the trend K 1 (α-CD)>K 1 (β-CD)>>K 1 (-CD), which can be explained by considering the influence of the CD cavity volume on the host-guest interactions. From the comparison of the K 1 values obtained for dodecyltriethylammonium bromide, DTEAB, to those estimated for the surfactants with the substituents, it was found that the incorporation of a phenoxy group at the end of the hydrocarbon tail does not affect K 1 , and the inclusion of a naphthoxy group has some influence on the association process, slightly diminishing K 1 . This makes evident the importance of the contribution of hydrophobic interactions to the binding, the length of the hydrophobic chain being the key factor determining K 1 . However, the presence of the aromatic rings does influence the location of the host and the guest in the inclusion complexes. The observed NOE interactions between the aromatic protons and the CD protons indicate that the aromatic rings are partially inserted within the host cavity, with the cyclodextrin remaining close to the aromatic rings, which could be partially intercalated in the host cavity. To the authors´ knowledge this is the first study on the association of cyclodextrins with monomeric surfactants incorporating substituents at the end of the hydrophobic tail.

Preparation and Characterization of New Liposomes. Bactericidal Activity of Cefepime Encapsulated into Cationic Liposomes

“…l -α-phosphatidylcholine (PC) from egg yolk, 1,2-dioleoyl- sn -glycero-3-phosphoethanolamine (DOPE), and cholesterol (CH) were purchased from Sigma-Aldrich and used as supplied. The N , N , N -triethyl- N -(12-naphthoxydodecyl)ammonium surfactant (12NBr) was synthesized and characterized as reported in Reference [ 20 ]. Cefepime (see Figure 1 ) and chloroform (analytical grade) were from Normon (Madrid, Spain) and Merck (Mollet del Vallès, Barcelona, Spain), respectively, and used as received.…”

“…Cationic and anionic liposomes were prepared by using the lipid film hydration method [ 20 , 21 ] with diverse modifications depending on the used lipids. In order to prepare lipid bilayers, lipids were first dissolved in chloroform.…”

Metallo-Liposomes of Ruthenium Used as Promising Vectors of Genetic Material

“…Liposomes were prepared by using the lipid thin-film hydration method [39,40]. First, appropriate quantities of DOPE and ruthenium-based lipids were dissolved in 2 mL chloroform.…”

Controlled Formation of Hydrated Micelles by the Intervention of Cyclodextrins

“…Martín et al reported on host-guest interactions between CDs and surfactants with functional groups at the end of the hydrophobic tail. [31] They intended to study the binding of cationic surfactants with a dodecyl hydrocarbon chain, a triethylammonium head group and aromatic substituent incorporated at the end of the surfactant tail to the CDs. Herein, we have used 1 as a fluorescent probe to study the extent of penetration of water molecules in the micelles formed by the CD-surfactant conjugates.…”