Abstract
The study of Langmuir monolayers incorporating biomimetic and bioactive substances plays an important role today in assessing the properties and quality of the molecular films for potential biomedical applications. Here, miscibility of binary and ternary monolayers of phospholipid (dioleoyl phosphatidylcholine, DOPC), immunosuppressant (cyclosporine A, CsA), and antioxidant (lauryl gallate, LG) of varying molar fractions was analyzed by means of the Langmuir technique coupled with a surface potential (ΔV) module at the air–water interface. The surface pressure–area per molecule (π–A) isotherms provided information on the physical state of the films at a given surface pressure, the monolayer packing and ordering, and the type and strength of intermolecular interactions. Surface potential–area (ΔV–A) isotherms revealed the molecular orientation changes at the interface upon compression. In addition, the apparent dipole moment of the monolayer-forming molecules was determined from the surface potential isotherms. The obtained results indicated that the film compression provoked subsequent changes of CsA conformation and/or orientation, conferring better affinity for the hydrocarbon environment. The mutual interactions between the components were analyzed here in terms of the excess and total Gibbs energy of mixing, whose values depended on the stoichiometry of the mixed films. The strongest attraction, thus the highest thermodynamic stability, was found for a DOPC–CsA–LG mixture with a 1:1:2 molar ratio. Based on these results, a molecular model for the organization of the molecules within the Langmuir film was proposed. Through this model, we elucidated the significant role of LG in improving the miscibility of CsA in the model DOPC membrane and thus in increasing the stability of self-assembled monolayers by noncovalent interactions, such as H-bonds and Lifshitz–van der Waals forces. The above 1:1:2 combination of three components is revealed as the most promising film composition for the modification of implant device surfaces to improve their biocompatibility. Further insight into mechanisms concerning drug–membrane interactions at the molecular level is provided, which results in great importance for biocoating design and development as well as for drug release at target sites.
Highlights
Ultrathin films characterized by high homogeneity, continuity, defined composition, and chemical structure as well as defined stability and wettability are used to modify the surface properties of implants
Taking together the findings presented in this paper as well as those published previously the probable mechanism of molecular interactions between DOPC, Cyclosporine A (CsA), and lauryl gallate (LG) is discussed below
Surface pressure versus area per molecule isotherms (π−A isotherms) for one- and multicomponent Langmuir monolayers incorporating the phospholipid DOPC, the immunosuppressant CsA, and the antioxidant LG were recorded at the air−water interface
Summary
Ultrathin films characterized by high homogeneity, continuity, defined composition, and chemical structure as well as defined stability and wettability are used to modify the surface properties of implants In this context, the physicochemical characteristics of Langmuir (L) and Langmuir-Blodgett (LB) monolayers, well-known ultrathin films, are part of intensive research in biomimetic systems.[1−3] The integration of these ultrathin films with the tissue strictly depends on the immune response of the organism, which is determined, among others, by the degree of biocompatibility of the material with cells.[4] One of the ways to improve biocompatibility is to modify the implant surface with a biocompatible living tissue layer of the desired physicochemical properties, which would prevent activation of the immune system, infection, and rejection of the implant.[2,3] In this aspect, there is a need for the preparation and characterization of multicomponent Langmuir films containing cell-friendly components of natural biological membranes (phospholipids, PL), as well as compounds with immunosuppressive activity (cyclosporine A, CsA) and antioxidant (lauryl gallate, LG).
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