LAUSR

Chitosan (Ch) is a polysaccharide mainly used in cosmetics, biotechnology and medicine owing to its biocompatibility, biodegradability and low cytotoxicity. One of the challenges is the development of mechanisms responsible for its action in biomedical applications. In this aspect, it is important to get more profound insight into the chitosan interactions with peptide drugs at the molecular level. The drug of interests was a cyclosporine A (CsA) known for its effective immunosuppressive action against transplant rejection. In this study, the Langmuir technique was used to determine the interactions between Ch (dissolved in the subphase) and the monomolecular films of CsA spread at the air–chitosan solution interface. The surface pressure versus the area per molecule (π–A) measurements of the CsA monolayers on the subphase with or without Ch was conducted at 20 °C and 37 °C. The Ch insertion into the CsA monolayers was monitored by relative changes in the $$\frac{\Delta A}{A}$$ΔAA area and the compression modulus. The findings demonstrate that the presence of Ch in the subphase provides the CsA monolayer expansion and affects the molecular packing and ordering in the temperature-dependent way. The temperature increase induces conformational changes in the peptide monolayers being a decisive factor which influences the kind and strength of interactions between Ch and CsA.