Monika Rojewska

Surface properties and morphology of mixed POSS-DPPC monolayers at the air/water interface

From the point of view of the possible medical applications of POSS (polyhedral oligomeric silsesquioxanes), it is crucial to analyse interactions occurring between POSS and model biological membrane at molecular level. Knowledge of the interaction between POSS and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) allows prediction of the impact of POSS contained in biomaterials or cosmetics on a living organism. In the study presented, the surface properties and morphology of Langmuir monolayers formed by mixtures of POSS and the phospholipid (DPPC) at the air/water surface are examined. We selected two POSS derivatives, with completely different chemical structure of substituents attached to the corner of the silicon open cage, which allowed the analysis of the impact of the character of organic moieties (strongly hydrophobic or clearly hydrophilic) on the order of POSS molecules and their tendency to form self-aggregates at the air/water surface. POSS derivatives significantly changed the profile of the π-A isotherms obtained for DPPC but in different ways. On the basis of the regular solution theory, the miscibility and stability of the two components in the monolayer were analysed in terms of compression modulus (Cs-1), excess Gibbs free energy (ΔGexc), activity coefficients (γ) and interaction parameter (ξ). The results obtained indicate the existence of two different interaction mechanisms between DPPC and POSS which depend on the chemical character of moieties present in POSS molecules.

Adsorption properties of biologically active derivatives of quaternary ammonium surfactants and their mixtures at aqueous/air interface II. Dynamics of adsorption, micelles dissociation and cytotoxicity of QDLS.

The main aim of our study was analysis of adsorption dynamics of mixtures containing quaternary derivatives of lysosomotropic substance (QDLS). Two types of equimolar mixtures were considered: the ones containing two derivatives of lysosomotropic substances (DMALM-12 and DMGM-12) as well as the catanionic mixtures i.e. the systems containing QDLS and DBSNa. Dynamic surface tension measurements of surfactant mixtures were made. The results suggested that the diffusivity of the mixed system could be treated as the average value of rates of diffusion of individual components, micelles and ion pairs, which are present in the mixtures studied. Moreover, an attempt was made to explain the influence of the presence of micelles in the mixtures on their adsorption dynamics. The compounds examined show interesting biological properties which can be useful, especially for drug delivery in medical treatment. In vitro cytotoxic activities of the mixtures studied towards human cancer cells were evaluated. Most of the mixtures showed a high antiproliferative potential, especially the ones containing DMALM-12. Each cancer cell line used demonstrated different sensitivity to the same dose of the mixtures tested.

Selection of surfactants as main components of ecological wetting agent for effective extinguishing of forest and peat-bog fires

The results of research into obtaining an ecological wetting agent for wildfires are presented. First, measurements of the equilibrium and dynamic surface tension for anionic and non-ionic commercial surfactants and their binary mixtures were conducted. Next, the parameters of adsorption facilitating a quantitative description of the process in both binary systems as well as single-component solutions were estimated. In addition, the static and dynamic contact angles on model surfaces with different hydrophobicity were studied (glass, polyethylene, pressed peat). In a few mixed systems, a synergism in reducing the critical micelle concentration and/or a synergy of the ability to wetting model surfaces was identified. Next, research into the sorptivity and wettability of peat (loose and pressed) was conducted. It was found that non-ionic and anionic surfactants exhibit different abilities in respect of foaming and moistening of peat. From an analysis of the preliminary results, the surface-active components were selected to obtain a wetting agent composition. The wettability and adsorption characteristics and an evaluation of the foaming ability using solutions of the prepared compositions were tested. The effectiveness of the wetting composition thus obtained was confirmed in the laboratory and in field firefighting. The test results confirmed the better wettability and sorptivity on peat and the effectivity for combating wildfires, compared with some typical commercial products.

The wettability and swelling of selected mucoadhesive polymers in simulated saliva and vaginal fluids

The surface properties play a particularly important role in the mucoadhesive drug delivery systems. In these formulations, the adsorption of polymer matrix to mucous membrane is limited by the wetting and swelling process of the polymer structure. Hence, the performance of mucoadhesive drug delivery systems made of polymeric materials depends on multiple factors, such as contact angle, surface free energy and water absorption rate. The aim of our study was to analyze the effect of model saliva and vaginal fluids on the wetting properties of selected mucoadhesive (Carbopol 974P NF, Noveon AA-1, HEC) and film-forming (Kollidon VA 64) polymers as well as their blends at the weight ratio 1:1 and 1:1:1, prepared in the form of discs. Surface properties of the discs were determined by measurements of advancing contact angle on the surface of polymers and their blends using the sessile drop method. The surface energy was determined by the OWRK method. Additionally, the mass swelling factor and hydration percentage of examined polymers and their blends in simulated biological fluids were evaluated.

Preparation and characterisation of monolayers and Langmuir–Blodgett films of liquid crystal mixed with cubic silsesquioxanes

ABSTRACT Polyhedral oligomeric silesquioxanes (POSS) with eight polyether substituents were mixed with the liquid crystal (LC) 4-octyloxy-4′-cyanobiphenyl and spread at the air/water interface. The surface pressure-area and surface potential-area isotherms were recorded for different weight ratios of both components. The obtained results showed that POSS molecules had beneficial influence on LC monolayer improving its stability and rigidity. Moreover, it was found that some LC–POSS mixtures collapse reversibly and form multilayer films on the top of LC monolayer. On the other hand, interfacial dilatational and shear rheology indicated decrease of elasticity of the films after mixing. Brewster angle microscopy revealed multilayer structure of the condensed film and formation of net-like structures in the expanded film. These films were successfully transferred on solid substrates using the Langmuir–Blodgett technique. The scanning electron microscopy images confirmed the film deposition and formation of networks by POSS–LC mixtures. These findings may be useful in the fabrication of electronic devices based on LCs. Graphical Abstract

Surface and swelling properties of mucoadhesive blends and their ability to release fluconazole in a mucin environment

The aim of this study is to characterize the matrices for the controlled release of fluconazole and to expand the knowledge of their physicochemical properties that influence the process of mucoadhesion. Polymeric carriers of fluconazole were prepared using the following mucoadhesive polymers: Carbopol 974 P NF, Noveon AA-1, HPMC, HEC, chitosan and film-forming polymer Kollidon VA 64. The potential mucoadhesive properties of the polymers and their blends were evaluated by measuring the wettability and then calculating the surface free energy defined by OWRK and vOCG models, determining the polar and dispersion forces, spreading coefficients and work of adhesion of polymers and their blends with fluconazole in the form of tablets. Prepared tablets were characterized by swelling capacity and in vitro drug release to estimate the amount of fluconazole release from selected polymer blends. The study of drug release from selected blends both in simulated saliva fluid (pH = 6.8) and in simulated vaginal fluid (pH = 4.2) containing mucin confirmed the ability of polymeric carriers to continuously deliver drug over a period of about 8 h.