Encapsulating properties of sulfobutylether-β-cyclodextrin toward a thrombin-derived antimicrobial peptide

The pharmacological application of antimicrobial peptides (AMPs) is seriously limited as they are not chemically and physically stable. Their encapsulation could represent a way to protect AMPs improving their pharmacological properties. In this study, the complex between the sulfobutylether-b-cyclodextrin (SBE-b-CD) and the antimicrobial peptide (P)GKY20 and its effect on a lipid bilayer have been characterized by a combination of calorimetric (ITC, DSC) and spectroscopic (fluorescence, Circular Dichroism) techniques. The results obtained indicate that the (P)GKY20 form a 1:1 inclusion complex with the anionic SBE-b-CD. Our ITC experiments revealed that the interaction process is entropically driven and that the enthalpy change only slightly contributes to the free energy change. Finally, differential scanning calorimetry data revealed that the peptide, even in the presence of SBE-b-CD, is still able to perturb the bacterial model membrane composed of DPPC/DPPG (8/2 mol mol-1). This work demonstrated that, in principle, SBE-b-CD could be used as efficient encapsulating agent for the (P)GKY20 or other antimicrobial peptides, rendering possible their pharmacological applications.