[Regeneration of corneal epithelium using keratin modified chitosan membranes]

The cornea is a transparent front layer of the eye. It functions like a window that controls and focuses the light entering into the eye. The cornea contributes to 65-75% of the eye's total focusing power and it acts as a physical barrier against pathogenic microorganisms, dirt and other noxious physical factors. The corneal tissue is arranged in five basic layers. The outermost layer (epithelium) is made up of highly regenerative cells that allow for quick healing of superficial injuries. Eye infections, diseases, or mechanical injury can harm corneal epithelium and cause blindness. Under certain circumstances, to prevent that, it is recommended to perform complete corneal transplantation. However, due to lack of sufficient number of donors, researchers are searching for alternative solutions.. Regeneration of epidermal tissue can restore and ensure normal functioning of cornea. For that purpose proper grafts are needed. The goal of current research was to develop the material for scaffold preparation providing optimal conditions for the epithelium cornea cell culturing and to determine its chemical, physical, and biological properties. The scaffolds, which could be applied in ophthalmology should fulfill a lot of requirements, among them such as biocompatibility, biodegradability, restorability, non-toxicity. They should also have adequate mechanical strength, flexibility and porosity. The aim of this work was to synthesize and to determine the properties of polymeric material for ophthalmic surgery applications. A hydrogel scaffold in the form of membrane was obtained from chitosan - natural, biocompatible, biologically inert, stable in the natural environmental and antibacterial polysaccharide derived from chitin. Biodegradable chitosan films containing keratin were crosslinked with genipin - a naturally occurring and nontoxic agent. In this study we present physicochemical characterization of the scaffolds. Porosity, contact angle and swelling ratio (at different pH) were determined. The optical microscope technique was used to visualize the microstructure of the scaffolds. Atomic force microscopy (AFM) measurements revealed the topography of the surfaces of membranes. The biological tests have shown that epithelial cells seeded on the membranes proliferated efficiently.

Interaction of curcumin with lipid monolayers and liposomal bilayers

Curcumin shows huge potential as an anticancer and anti-inflammatory agent. However, to achieve a satisfactory bioavailability and stability of this compound, its liposomal form is preferable. Our detailed studies on the curcumin interaction with lipid membranes are aimed to obtain better understanding of the mechanism and eventually to improve the efficiency of curcumin delivery to cells. Egg yolk phosphatidylcholine (EYPC) one-component monolayers and bilayers, as well as mixed systems containing additionally dihexadecyl phosphate (DHP) and cholesterol, were studied. Curcumin binding constant to EYPC liposomes was determined based on two different methods: UV/Vis absorption and fluorescence measurements to be 4.26×10(4)M(-1) and 3.79×10(4)M(-1), respectively. The fluorescence quenching experiment revealed that curcumin locates in the hydrophobic region of EYPC liposomal bilayer. It was shown that curcumin impacts the size and stability of the liposomal carriers significantly. Loaded into the EYPC/DPH/cholesterol liposomal bilayer curcumin stabilizes the system proportionally to its content, while the EYPC/DPH system is destabilized upon drug loading. The three-component lipid composition of the liposome seems to be the most promising system for curcumin delivery. An interaction of free and liposomal curcumin with EYPC and mixed monolayers was also studied using Langmuir balance measurements. Monolayer systems were treated as a simple model of cell membrane. Condensing effect of curcumin on EYPC and EYPC/DHP monolayers and loosening influence on EYPC/DHP/chol ones were observed. It was also demonstrated that curcumin-loaded EYPC liposomes are more stable upon interaction with the model lipid membrane than the unloaded ones.

Behavior of 2,6-bis(decyloxy)naphthalene inside lipid bilayer

Interactions between small organic molecules and lipid or cell membranes are important because of their role in the distribution of biologically active substances inside the membrane and their permeation through the cell membranes. In the current paper, we have explored the effect of the attachment of long hydrocarbon tails on the behavior of small organic molecule inside the lipid membrane. Naphthalene with two decyloxy groups attached at the opposite sites of the ring (2,6-bis(decyloxy)naphthalene, 3) was synthesized and incorporated into phosphatidylcholine (PC) vesicles. Fluorescence methods as well as molecular dynamic (MD) simulations were used to estimate the position, orientation, and migration of compound 3 in PC bilayer. It was found that the naphthalene ring of compound 3 resides in the upper acyl chain region of the bilayer and the hydrocarbon tails are directed to the center of the bilayer. As was shown with cryotransmission electron microscopy (cryo-TEM), such lipidlike conformation enables compound 3 to be incorporated into liposomes at a very high content without their disintegration. Moreover, compound 3 can migrate from one leaflet to other. The mechanism of this process is, however, different from that characteristic of the flip-flop event of lipid molecules in the membrane. Finally, the possible application of compound 3 as a rotational molecular probe for monitoring fluidity of liposomal membrane in the acyl side chain region was checked by studies of the effect of cholesterol on the fluorescence anisotropy of 3.

Molecular structure of the dioctadecyldimethylammonium bromide (DODAB) bilayer

Dioctadecyldimethylammonium bromide (DODAB) is a double-chained quaternary ammonium surfactant that assembles in water into bilayer structures. This letter reports the molecular dynamics (MD) computer simulations of the DODAB bilayer at 25 °C. The simulations show that the surfactant membrane arranges spontaneously into the rippled phase (P(β)(')) at that temperature. The ordering within the chain fragment closest to the hydrophilic head (carbon atoms 1-5) is relatively low. It grows significantly for the carbon atoms located in the center of the membrane (atoms 6-17). The C6-C17 chain fragments are well aligned and tilted by ca. 15° with respect to the bilayer normal.

Nanoheterogeneous multilayer films with perfluorinated domains fabricated using the layer-by-layer method

Nanoheterogenous ultrathin films containing perfluorinated domains were prepared via the layer-by-layer (LbL) electrostatic self-assembly method. The films are constructed from the amphiphilic cationic copolymer with perfluorinated side chains and poly(sodium styrenesulfonate) (PSS). The LbL process was optimized by the application of sonication which allowed linear growth of the film. The resulting film exhibited micellar structure with isolated fluorocarbon hydrophobic domains. The remarkable features of the films were their switchable wettability and friction properties. The obtained water-processable films can find a number of potential applications, e.g., as smart and low friction coatings.

Chitosan derivatives as novel potential heparin reversal agents

In emergency cases anticoagulant action of heparin needs to be stopped instantaneously, which is usually achieved by intravenous administration of protamine sulfate (PS). However, PS shows many adverse effects. The objective of the present work was to find out if chitosan (Ch) and a cationically modified chitosan, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride (HTCC), may be applied for heparin reversal. For chitosan the efficiency of unfractionated heparin (UFH) binding decreases with increasing pH while for cationically modified chitosan heparin binding is efficient even for high pH values. Complexation of UFH and low-molecular-weight heparin (LMWH) by cationically modified chitosan in the aqueous solution at pH = 7.4 was studied. Complexes of the modified chitosan with UFH are smaller and of lower dispersity than those with PS. Cationically modified chitosan was found to bind both UFH and LMWH. The complex formation capability of cationically modified chitosan is comparable to that of PS.

Spontaneous formation of densely stacked multilamellar vesicles in dioctadecyldimethylammonium bromide/oleosiloxane mixtures

A double-tailed surfactant, for example, dioctadecyldimethylammonium bromide (DODAB), tends to form bilayer fragments rather than vesicles in aqueous solution upon sonication. This Letter reports on the morphological transformations of the membrane fragments leading to multilamellar vesicle formation. The surfactant membranes were swollen with tetra(11-methoxy-11-oxoundecyl)tetramethylcyclotetrasiloxane (3) (a cyclosiloxane with covalently attached fatty-acid esters) up to 50 mol % based on the surfactant content. That compound was synthesized by hydrosilylation of 1,3,5,7-tetramethylcyclotetrasiloxane with four molecules of methyl undec-10-enoate. Using cryo-transmission electron microscopy (cryo-TEM), it has been shown that densely stacked multilamellar vesicles form spontaneously in the sonicated DODAB dispersion containing 50 mol % of the compound 3 after adjusting pH to the value of 9.5. This occurs as a result of the hydrolysis of ester bonds of the compound 3 inside the membrane with formation of tetra(11-carboxyundecyl)tetramethylcyclotetrasiloxane (4). The carboxylic groups in compound 4 are ionized under experimental conditions. That results in the appearance of the negative charge at the surface which neutralizes the positively charged molecules of DODAB, thus reducing repulsive interactions between the membrane fragments. Additionally, as was shown using Langmuir monolayer measurements, the presence of compound 4 expands the DODAB film and decreases its bending rigidity. That makes the bending process considerably easier and promotes formation of multilamellar vesicles.

Hypochlorous acid: a natural adjuvant that facilitates antigen processing, cross-priming, and the induction of adaptive immunity

The production of hypochlorous acid (HOCl) is a characteristic of granulocyte activation, a hallmark of the early phase of innate immune responses. In this study, we show that, in addition to its well-established role as a microbicide, HOCl can act as a natural adjuvant of adaptive immunity. HOCl enhances the T cell responses to the model Ag OVA, facilitating the processing and presentation of this protein via the class II MHC pathway. HOCl modification also enhances cross-presentation of the tumor Ag tyrosinase-related protein 2 via class I MHC. The adjuvant effects of HOCl are independent of TLR signaling. The enhanced presentation of HOCl-modified OVA is mediated via modification of the N-linked carbohydrate side chain rather than formation of protein aldehydes or chloramines. HOCl-modified OVA is taken up more efficiently by APCs and is degraded more efficiently by proteinases. Atomic force microscopy demonstrated that enhanced uptake is mediated via specific receptor binding, one candidate for which is the scavenger receptor lectin-like oxidized low-density lipoprotein receptor, which shows enhanced binding to chlorinated OVA. A function of HOCl is therefore to target glycoprotein Ags to scavenger receptors on the APC surface. This additional mechanism linking innate and adaptive immunity suggests novel strategies to enhance immunity to vaccines.

Comparison of photodynamic efficacy of tetraarylporphyrin pegylated or encapsulated in liposomes: in vitro studies

Two photosensitizing systems: (1) tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) encapsulated in sterically stabilized liposomes (SSL) and (2) p-THPP functionalized by covalent attachment of poly(ethylene glycol) (p-THPP-PEG(2000)) were studied in vitro. The dark and photo cytotoxicity of these systems were evaluated on two cell lines: HCT 116, a human colorectal carcinoma cell line, and DU 145, a prostate cancer cell line and compared with these determined for free p-THPP. It was demonstrated that both encapsulation in liposomes as well as attachment of PEG chain result in pronounced reduction of the dark cytotoxicity of the parent porphyrin. The liposomal formulation showed higher than p-THPP-PEG(2000) photocytotoxicity towards both cell lines used in the studies.

Hybrid silica-silicone nanocapsules obtained in catanionic vesicles. Cryo-TEM studies

An effective way to obtain hollow hybrid silica-silicone nanocapsules of controlled diameter is presented. For that purpose a new precursor of silica-silicone material, tetra(triethoxysilylethyl) tetramethylcyclotetrasiloxane, was synthesized by hydrosilylation of vinyltriethoxysilane with tetramethylcyclotetrasiloxane. Mixture of dodecyltrimethylammonium bromide (DTAB) and sodium dodecylbenzenesulfonate (SDBS) in the cationic (the DTAB/SDBS system) rich region of the phase diagram was used to form the vesicular templates. The hybrid silica-silicone nanocapsules was obtained in base-catalyzed polymerization/polycondensation processes of the precursor inside of vesicle membrane. The shape and morphology of the silica-silicone nanocapsules was evaluated using transmission cryo-electron microscopy (cryo-TEM). Cryo-TEM reveals formation of discrete hollow shells of diameter consisted with the sizes of equilibrium vesicles used for templating.