Thermal properties of adamantanol derivatives and their beta-cyclodextrin complexes in phosphatidylcholine bilayers.

Differential Scanning Calorimetry (DSC) has been applied to study the thermal properties of the membrane perturbing antibacterial octyl- and dodecyl-bromide salts of quaternary dimethylamino adamantanol (ADM-8 and ADM-12 correspondingly) incorporated in free or complexed form with beta-cyclodextrin (beta-CD) into dipalmitoylphosphatidylcholine (DPPC) containing bilayers. The DSC results showed that the studied compounds exert pronounced thermotropic changes in DPPC bilayers when inserted as free molecules. These effects are reduced when are present in a complex form with beta-CD. Since the studied compounds exert destructive effects in membrane bilayers their insertion in membrane bilayers as complexes with cyclodextrin may result in differentiation of their activity. The obtained results suggest that their complexation with beta-CD may improve their biological profile. It also increases their aqueous solubility, a limited factor for their use as drugs.