Spontaneous association of hydrophobized dextran and poly-β-cyclodextrin into nanoassemblies.: Formation and interaction with a hydrophobic drug

New nanoassemblies were instantaneously prepared by mixing two aqueous solutions, one containing a β-cyclodextrin polymer (pβCD), and the other a hydrophobically modified by alkyl chains dextran (MD). The formation mechanism and the inner structure of these nanoassemblies were analysed using surface tension measurements and 1H NMR spectroscopy. The effect of a hydrophobic guest molecule, such as benzophenone (BZ), on the formation and stability of the nanoassemblies was also evaluated. MD exhibited the typical behaviour of a soluble amphiphilic molecule and adsorbed at the air/water interface. Whereas the injection of native β-CDs in the solution beneath the adsorbed MD monolayer did not produce any change in the surface tension, that of the pβCD resulted in an increase in the surface tension, indicating the desorption of the polymer from the interface. This result accounts for a cooperative effect of β-CDs linked together in the pβCD polymer on dextran desorption. The presence of benzophenone in the system hindered the sequestration of dextran alkyl moieties by β-CD in the polymer without impeding the formation of associative nanoassemblies of 100–200 nm. 1H NMR investigations demonstrated that, in the BZ-loaded nanoassemblies, the hydrophobic molecule was mainly located into the cyclodextrin cavities.

The formation mechanism and the structure of cyclodextrin based nanoassemblies were investigated. A cooperative effect between several cyclodextrins linked together was essential to sequestrate MD polymer from the air/water interface.Figure optionsDownload as PowerPoint slide