Functional characterisation of novel analgesic product based on self-regulating drug carriers.

We compared a new formulation of ketoprofen (Diractin) based on ultradeformable vesicle (Transfersome) carriers with conventional topical gels with the drug (Gabrilen; Togal Mobil Gel; Fastum). Depending on water concentration, between a few percent and >95% of ketoprofen in Diractin is associated with the vesicles. The low free drug concentration on open skin (1-3%) minimises ketoprofen diffusion from Diractin through the organ, keeping effective permeability coefficient for the product (even after increase to approximately 3.5 x 10(-3) cm h(-1) at 24h) below that of conventional gels ( approximately 0.3-2.1 x 10(-1) cm h(-1)). The carrier's stress-responsiveness enables constriction crossing without vesicle breakdown. The carrier stiffening upon dilution, e.g. in tissues below the skin's diffusive barrier, helps avoiding the drug uptake in cutaneous blood capillaries. Diractin therefore can deposit ketoprofen in deep subcutaneous tissues, which the drug from conventional gels reaches mainly via systemic circulation. In vitro efficacy of daily drug delivery through skin is < or =1.6% for conventional topical NSAID gels and merely approximately 0.05% for Diractin. In contrast, in vivo ketoprofen transport by ultradeformable carriers through non-occluded skin into living pigs' subcutaneous muscles is 5-14x better than for conventional gels. Locally targeted drug transport by the self-regulating, ultradeformable vesicles is thus clearly non-diffusive and quite efficient.

Time-resolved X-ray reflectivity measurements of protein binding onto model lipid membranes at the air-water interface.

The energy-dispersive X-ray reflectometry and turbidity measurements are used to investigate the kinetics of concanavalin A binding onto the distearoylphosphatidylcholine/distearoylphosphatidylethanolamine-+ ++maltobionamide (DSPC/DSPE-mal1) or distearoylphosphatidylcholine/distearoylphosphatidylethanolamine-+ ++maltotetrabionamide (DSPC/mal3) mixed monolayer at the air-water interface. The resulting adsorbed layer of this sugar-binding protein near the membrane with one or three hexoses in the lipid head-group is 3.9 nm or 9.7 nm thick, respectively. The different thicknesses of the adsorbed layer can be correlated with the diverse orientations of the adsorbed proteins. These lay flat on the surface containing DSPE-mal1 and 'perpendicular' to the surface containing DSPE-mal3. The monolayer structure is little affected by concanavalin A binding, but the incorporation of sugar lipids decreases the chain tilt and the interfacial thickness marginally. The binding is quasi-exponential with the time constant between some minutes and several hours depending on the concanavalin A and vesicle concentrations in the bulk. The experimental resolution of the time-resolved measurements made with the laboratory-based instrument is 15 min and the spatial resolution is between 0.05 nm and 0.5 nm, depending on the electron contrast. It is estimated that the high-brilliance synchrotron X-ray source combined with the detection method outlined in this work, could permit the kinetic measurements on the time-scale of < 1 minute.

Energy-dispersive X-ray reflectivity study of the model membranes at the air/water interface.

The results of the first energy-dispersive reflectivity measurements with a (membrane coated) liquid surface are reported. They rely on the calibration curve measured with pure water and can be done without any sample or detector movement with a low-intensity, laboratory-based X-ray generator within less than 1 h. As an illustration, the structural parameters of a diarachidoylphosphatidylcholine monolayer at the air/water interface are determined. It is argued that the energy-dispersive detection in combination with the intense synchrotron radiation can be used for the time-resolved reflectivity measurements on the time-scale of minutes.

EDTA-induced self-assembly of cationic lipid-DNA multilayers near a monolayer-covered air-water interface.

The presence of EDTA in the suspending buffer can induce the formation of multilayer structures from a mixture of the cationic lipid 3beta[N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol and the zwitterionic 'helper' lipid 1, 2-dimyristoyl-sn-glycero-3-phosphocholine with DNA. The resulting structures consist of stacks of alternating sheets of lipid bilayer with intercalated DNA. In the absence of EDTA, only a single layer of DNA adsorbs to the lipid membrane. The buffer composition therefore influences the morphology of the lipid-aggregate/DNA assembly, which was not known to date.

Solute effects on the colloidal and phase behavior of lipid bilayer membranes: ethanol-dipalmitoylphosphatidylcholine mixtures.

By means of the scanning differential calorimetry, x-ray diffractometry, and the dynamic light scattering, we have systematically studied the phase and packing properties of dipalmitoylphosphatidylcholine vesicles or multibilayers in the presence of ethanol. We have also determined the partial ternary phase diagram of such dipalmitoylphosphatidylcholine/water/ethanol mixtures. The directly measured variability of the structural bilayer parameters implies that ethanol binding to the phospholipid bilayers increases the lateral as well as the transverse repulsion between the lipid molecules. This enlarges the hydrocarbon tilt (by up to 23 degrees) and molecular area (by < or = 40%). Ethanol-phospholid association also broadens the interface and, thus, promotes lipid headgroup solvation. This results in excessive swelling (by 130%) of the phosphatidylcholine bilayers in aqueous ethanol solutions. Lateral bilayer expansion, moreover, provokes a successive interdigitation of the hydrocarbon chains in the systems with bulk ethanol concentrations of 0.4-1.2 M. The hydrocarbon packing density as well as the propensity for the formation of lamellar gel phases simultaneously increase. The pretransition temperature of phosphatidylcholine bilayers is more sensitive to the addition of alcohol (initial shift: delta Tp = 22 degrees C/mol) than the subtransition temperature (delta Ts reversible 5 degrees C/mol), whereas the chain-melting phase transition temperature is even less affected (delta Tm = 1.8 degrees C/mol). After an initial decrease of 3 degrees for the bulk ethanol concentrations below 1.2 M, the Tm value increases by 2.5 degrees above this limiting concentration. The gel-phase phosphatidylcholine membranes below Tm are fully interdigitated above this limiting concentration. The chain tilt on the fringe of full chain interdigitation is zero and increases with higher ethanol concentrations. Above Tm, some of the lipid molecules are solubilized by the bound ethanol molecules. More highly concentrated ethanol solutions (> 7 M) solubilize the phosphatidylcholine bilayers with fluid chains fully and result in the formation of mixed lipid-alcohol micelles.