Lipid vesicles and other colloids as drug carriers on the skin

Cutaneous short-interfering RNA therapy

Since the 1990s, RNA interference (RNAi) has become a major subject of interest, not only as a tool for biological research, but also, more importantly, as a therapeutic approach for gene-related diseases. The use of short-interfering RNAs (siRNAs) for the sequence-specific knockdown of disease-causing genes has led to numerous preclinical and even a few clinical studies. Applications for cutaneous delivery of therapeutic siRNA are now emerging owing to a strong demand for effective treatments of various cutaneous disorders. Although successful studies have been performed using several different delivery techniques, most of these techniques encounter limitations for translation to the clinic with regards to patient compliance. This review describes the principal findings and applications in cutaneous RNAi therapy and focuses on the promises and pitfalls of the delivery systems.

Ionic liquid-assisted transdermal delivery of sparingly soluble drugs

We report the first successful application of a novel IL-assisted non-aqueous microemulsion stabilized by a blend of two nontoxic surfactants, polyoxyethylene sorbitan monooleate (Tween-80), and sorbitan laurate (Span-20) for transdermal delivery of acyclovir, which is insoluble or sparingly soluble in water and most common organic liquids.

Evaluation of solid lipid microparticles produced by spray congealing for topical application of econazole nitrate

Objectives

The aims of this study were to evaluate the suitability of the spray congealing technique to produce solid lipid microparticles (SLMs) for topical administration and to study the skin permeation of a drug from SLMs compared with solid lipid nanoparticles (SLNs).

Methods

Econazole nitrate was used as model drug and Precirol ATO 5 as the lipidic carrier. SLMs and SLNs were both prepared at 5: 1, 10: 1 and 12.5: 1 lipid: drug weight ratios and characterised in terms of particle size, morphology, encapsulation efficiency and chemical analysis of the particle surface. SLMs and SLNs were also incorporated into HPMC K 100M hydrogels for ex-vivo drug permeation tests using porcine epidermis.

Key findings

SLMs had particle sizes of 18–45 μm, while SLNs showed a mean diameter of 130–270 nm. The encapsulation efficiency was 80–100%. Permeation profiles of econazole nitrate were influenced by both particle size (significant difference until 9 h) and the amount of lipid.

Conclusions

The results confirm the usefulness of SLNs as carriers for topical administration and suggest the potential of SLMs for the delivery of drugs to the skin.

A facile construction strategy of stable lipid nanoparticles for drug delivery using a hydrogel-thickened microemulsion system

We report a novel facile method for preparing stable nanoparticles with inner spherical solid spheres and an outer hydrogel matrix using a hot O/W hydrogel-thickened microemulsion with spontaneous stability. The nanoparticles with average diameters of about 30.0 nm and 100.0 nm were constructed by cooling the hot hydrogel-thickened microemulsion at different temperatures, respectively. We explained the application of these nanoparticles by actualizing the cutaneous delivery of drug-loaded nanoparticles. The in vitro skin permeation studies showed that the nanoparticles could significantly reduce the penetration of model drugs through skin and resulted in their dermal uptakes in skin. The sol-gel process of TEOS was furthermore used in the template of HTM to regulate the particle size of nanoparticles. The coating of silica on the surface of nanoparticles could regulate the penetration of drug into skin from dermal delivery to transdermal delivery. This strategy provides a facile method to produce nanoparticles with long-term stability and ease of manufacture, which might have a promising application in drug delivery.

Current trends in liposome research

Among the several drug delivery systems, liposomes--phospholipid nanosized vesicles with a bilayered membrane structure--have drawn a lot of interest as advanced and versatile pharmaceutical carriers for both low and high molecular weight pharmaceuticals. At present, liposomal formulations span multiple areas, from clinical application of the liposomal drugs to the development of various multifunctional liposomal systems to be used in therapy and diagnostics. This chapter provides a brief overview of various liposomal products currently under development at experimental and preclinical level.

Carriers in the topical treatment of skin disease

Topical drug application is less prone to severe systemic side-effects than systemic application. Starting with the liposomes, various types of nanosized and microsized drug carriers have been developed to increase the notoriously low penetration of active agents into the skin, which limits not only the topical therapy of skin disease but also transdermal therapy. Today, liposome- and microsponge-based preparations are approved for dermatomycosis, acne and actinic keratosis. Under investigation are drug carriers such as lipid nanoparticles, polymeric particles, dendrimers, and dendritic-core multi-shell nanotransporters. According to the rapidly increasing research in this field, both in academia and industry, a breakthrough appears likely, once stability problems (nanoparticles) and safety concerns (dendrimers) are overcome. Technical approaches and results of in vitro, ex vivo and in vivo testing are described, taking into account pharmacokinetic, efficacy and safety aspects.

Effect of size at the nanoscale and bilayer rigidity on skin diffusion of liposomes

This study reports the effect of liposome particle size at the nanoscale and bilayer deformability on the permeation through MatTek human skin equivalents and provides a comparative quantitative measure through calculation of diffusion coefficients. Exploring DOPC and DPPC fluorescent liposomes, our results demonstrate the faster diffusion of 50 nm liposomes compared with 100 and 200 nm liposomes when the lipid bilayer remains the same. Diffusion kinetics of the 50 nm particles appear not to depend on the rigidity of the lipid layer, whereas diffusion of particles larger than 100 nm is significantly affected by the rigidity of the bilayer, and DOPC liposomes diffuse faster than their DDPC equivalents. Our results suggest that liposomes composed of a rigid bilayer can be expected to remain intact after passing through the stratum corneum.

Preparation and characterization of a lecithin nanoemulsion as a topical delivery system

Purpose of this study was to establish a lecithin nanoemulsion (LNE) without any synthetic surfactant as a topical delivery vehicle and to evaluate its topical delivery potential by the following factors: particle size, morphology, viscosity, stability, skin hydration and skin penetration. Experimental results demonstrated that an increasing concentration of soybean lecithin and glycerol resulted in a smaller size LNE droplet and increasing viscosity, respectively. The droplet size of optimized LNE, with the glycerol concentration above 75% (w/w), changed from 92 (F10) to 58 nm (F14). Additionally, LNE, incorporated into o/w cream, improved the skin hydration capacity of the cream significantly with about 2.5-fold increase when the concentration of LNE reached 10%. LNE was also demonstrated to improve the penetrability of Nile red (NR) dye into the dermis layer, when an o/w cream, incorporated with NR-loaded LNE, applied on the abdominal skin of rat in vivo. Specifically, the arbitrary unit (ABU) of fluorescence in the dermis layer that had received the cream with a NR-loaded LNE was about 9.9-fold higher than the cream with a NR-loaded general emulsion (GE). These observations suggest that LNE could be used as a promising topical delivery vehicle for lipophilic compounds.

Surface charged temoporfin-loaded flexible vesicles: in vitro skin penetration studies and stability

In order to increase topical delivery of temoporfin (mTHPC), a highly hydrophobic photosensitizer with low percutaneous penetration, neutral, anionic and cationic flexible liposomes (i.e. flexosomes) were prepared and investigated for their penetration enhancing ability. The in vitro skin penetration study was performed using human abdominal skin mounted in Franz diffusion cells. Besides the effect of surface charge of flexosomes on skin penetration of mTHPC, also its effect on physical properties (particle size, polydispersity index, lamellarity) and physicochemical stability of vesicles was investigated. Photon-correlation spectroscopy revealed that vesicles had after preparation a small particle size and low polydispersity index, while cryo-electron microscopy confirmed that these vesicles were mostly unilamellar and of a spherical shape. Regarding stability, contrasting to anionic flexosomes showing lack of long-term stability, neutral and cationic flexosomes were stable during 9 months storage at 4 degrees C. As to the penetration enhancing ability, cationic flexosomes possessed the highest, i.e. they delivered the highest mTHPC-amount to stratum corneum and deeper skin layers compared to conventional liposomes, neutral and anionic flexosomes. In conclusion, mTHPC-loaded cationic flexosomes could be a promising tool for delivering mTHPC to the skin, which would be beneficial for the photodynamic therapy of cutaneous malignant or non-malignant diseases.

Topical delivery of 5-aminolevulinic acid-encapsulated ethosomes in a hyperproliferative skin animal model using the CLSM technique to evaluate the penetration behavior

Psoriasis, an inflammatory skin disease, exhibits recurring itching, soreness, and cracked and bleeding skin. Currently, the topical delivery of 5-aminolevulinic acid-photodynamic therapy (ALA-PDT) is an optional treatment for psoriasis which provides long-term therapeutic effects, is non-toxic and enjoys better compliance with patients. However, the precursor of ALA is hydrophilic, and thus its ability to penetrate the skin is limited. Also, little research has provided a platform to investigate the penetration behavior in disordered skin. We employed a highly potent ethosomal carrier (phosphatidylethanolamine; PE) to investigate the penetration behavior of ALA and the recovery of skin in a hyperproliferative murine model. We found that the application of ethosomes produced a significant increase in cumulative amounts of 5-26-fold in normal and hyperproliferative murine skin samples when compared to an ALA aqueous solution; and the ALA aqueous solution appeared less precise in terms of the penetration mode in hyperproliferative murine skin. After the ethosomes had been applied, the protoporphyrin IX (PpIX) intensity increased about 3.64-fold compared with that of the ALA aqueous solution, and the penetration depth reached 30-80 microm. The results demonstrated that the ethosomal carrier significantly improved the delivery of ALA and the formation of PpIX in both normal and hyperproliferative murine skin samples, and the expression level of tumor necrosis factor (TNF)-alpha was reduced after the ALA-ethosomes were applied to treat hyperproliferative murine skin. Furthermore, the results of present study encourage more investigations on the mechanism of the interaction with ethosomes and hyperproliferative murine skin.

Dynamics of vesicle formation from lipid droplets: mechanism and controllability

A coarse-grained model developed by Marrink et al. [J. Phys. Chem. B 111, 7812 (2007)] is applied to investigate vesiculation of lipid [dipalmitoylphosphatidylcholine (DPPC)] droplets in water. Three kinds of morphologies of micelles are found with increasing lipid droplet size. When the initial lipid droplet is smaller, the equilibrium structure of the droplet is a spherical micelle. When the initial lipid droplet is larger, the lipid ball starts to transform into a disk micelle or vesicle. The mechanism of vesicle formation from a lipid ball is analyzed from the self-assembly of DPPC on the molecular level, and the morphological transition from disk to vesicle with increasing droplet size is demonstrated. Importantly, we discover that the transition point is not very sharp, and for a fixed-size lipid ball, the disk and vesicle appear with certain probabilities. The splitting phenomenon, i.e., the formation of a disk/vesicle structure from a lipid droplet, is explained by applying a hybrid model of the Helfrich membrane theory. The elastic module of the DPPC bilayer and the smallest size of a lipid droplet for certain formation of a vesicle are successfully predicted.

A new micro/nanoencapsulated porphyrin formulation for PDT treatment

The highly hydrophobic 5,10,15-triphenyl-20-(3-N-methylpyridinium-yl)porphyrin (3MMe) cationic species was synthesized, characterized and encapsulated in marine atelocollagen/xanthane gum microcapsules by the coacervation method. Further reduction in the capsule size, from several microns down to about 300-400 nm, was carried out successfully by ultrasonic processing in the presence of up to 1.6% Tween 20 surfactant, without affecting the distribution of 3MMe in the oily core. The resulting cream-like product exhibited enhanced photodynamic activity but negligible cytotoxicity towards HeLa cells. The polymeric micro/nanocapsule formulation was found to be about 4 times more phototoxic than the respective phosphatidylcholine lipidic emulsion, demonstrating high potentiality for photodynamic therapy applications.

Flexible polymerosomes--an alternative vehicle for topical delivery

Self-assembled vesicles of poly(caprolactone)-poly(ethylene glycol)-poly(caprolactone) co-polymer of 122+/-20 nm were prepared by solvent evaporation method and analyzed morphologically by TEM and AFM. Transmission electron micrographs showed the presence of double-walled deformable structures with average wall thickness of 25 nm. AFM depicted somewhat flattened tops resembling a 'pancake' further confirming the flexibility of the nanocarriers. Permeation studies of fluorescently labelled vesicles in cadaver epidermis confirmed their presence across the stratum corneum within 2h of application and accumulation in the deeper layers thereafter. The flexible nature of these nanosystems makes them an efficient alternative to liposomes for targeting melanomas and basal cell carcinomas.

Interactions of surfactants with lipid membranes

Surfactants are surface-active, amphiphilic compounds that are water-soluble in the micro- to millimolar range, and self-assemble to form micelles or other aggregates above a critical concentration. This definition comprises synthetic detergents as well as amphiphilic peptides and lipopeptides, bile salts and many other compounds. This paper reviews the biophysics of the interactions of surfactants with membranes of insoluble, naturally occurring lipids. It discusses structural, thermodynamic and kinetic aspects of membrane-water partitioning, changes in membrane properties induced by surfactants, membrane solubilisation to micelles and other phases formed by lipid-surfactant systems. Each section defines and derives key parameters, mentions experimental methods for their measurement and compiles and discusses published data. Additionally, a brief overview is given of surfactant-like effects in biological systems, technical applications of surfactants that involve membrane interactions, and surfactant-based protocols to study biological membranes.

Understanding the role of surface charges in cellular adsorption versus internalization by selectively removing gold nanoparticles on the cell surface with a I2/KI etchant

This Letter presents a new method for differentiating the Au nanospheres attached to the cell surface from those being internalized into the cells. We introduced an etching solution based on I2 and KI that can selectively dissolve the Au nanospheres on the cell surface within a short period of time. The advantage of this etchant is its low toxicity to the cells because it is capable of etching away a relatively large amount of Au nanospheres at a low molar concentration. By combining with quantitative elemental analysis, we found that the deposition of Au nanospheres on the surface of cancer cells was highly dependent on the sign of surface charges on the Au nanospheres. In addition, by fitting the uptake data with a kinetic model, we were able to derive the overall and internalization rate constants for Au nanospheres and both of them were found to be governed by the surface charges on Au nanospheres.

Self-dissolving microneedles for the percutaneous absorption of EPO in mice

Erythropoietin (EPO) loaded microneedles were prepared using thread-forming polymer as a base for the percutaneous administration of EPO. The used polymers were dextrin, chondroitin sulfate and albumin. Under room temperature, EPO solution was added to high concentration of polymer solution and microneedles were prepared by forming thread with polypropylene tips. The mean weight of microneedle was 0.59 +/- 0.01 mg and length and basal diameter were 3.24 +/- 0.16 and 0.55 +/- 0.03 mm, respectively. Four microneedles were percutaneously (pc) administered to mice at the EPO dose levels of 100 IU/kg. After administration, blood samples were collected for 24 h and serum EPO levels were measured. Dextrin EPO microneedles were administered both pc and subcutaneously (sc) to mice. Serum EPO levels vs. time profiles showed Cmax of 138.6 +/- 16.1 and 146.5 +/- 8.0 mIU/ml, respectively. Tmax were 7.5 h. The values of bioavailability (BA) of EPO were 82.1 and 99.4%, respectively. By decreasing the dose from 100 to 50 and 25 IU/kg, dose-dependent serum EPO levels vs. time profiles were not clearly obtained. When chondroitin sulfate and albumin were used as the microneedle base, the serum EPO levels vs. time profiles showed almost the same pattern. Cmax of chondroitin sulfate and albumin microneedles were 96.3 +/- 8.8 and 132.2 +/- 18.9 mIU/ml, respectively. AUCs were 835.1 and 1098.7 mIU h/ml. Tmax were 8 and 6.8 h. These results suggest the usefulness of microneedles for the percutaneous administration of EPO.

Self-dissolving micropiles for the percutaneous absorption of recombinant human growth hormone in rats

The feasibility of self-dissolving micropiles (SDMP) as a percutaneous delivery system of recombinant human growth hormone (rhGH) has been studied in rats using SDMP where dextran was used as a base. After mixing dextran solution with rhGH, SDMPs were prepared by pulling with polypropyrene tips. The mean weight, length and diameter were 0.68+/-0.05 mg, 3.2+/-0.5 mm and 0.6+/-0.2 microm, respectively. To evaluate the bioavailability (BA) of rhGH percutaneously administered by SDMP, an absorption experiment was performed in rats. RhGH SDMPs were inserted into the rats skin, 200 microg kg(-1), and plasma rhGH levels were measured by an ELISA method. Peak plasma rhGH level, 132.8+/-11.8 ng ml(-1), appeared at 0.8+/-0.2 h. By comparing the plasma rhGH levels vs. time profiles after the administration of SDMP and intravenous injection of rhGH solution, 5 microg kg(-1), BA of rhGH from SDMP was calculated to be 87.5%. Theses results may suggest that SDMP can be used as a novel percutaneous drug delivery system.

Pig skin structure and transdermal delivery of liposomes: a two photon microscopy study

In this work we have characterized the architecture and physical properties of pig skin epidermis including its permeability to different liposome formulations. Autofluorescence images show that cells in the epidermis, from the basal layer to the stratum corneum, are organized in clusters that are in turn separated by particular structures we named "canyons". These canyons start in the surface as a wrinkle, eventually closing and going all the way inside the epidermis as a distinct structure that reaches the stratum basale. This structure, described previously in the epidermis of mouse skin as "intercluster pathway", was suggested to be filled with an unknown material and offer low resistance to vesicle penetration. Analysis of LAURDAN Generalized Polarization images of pig skin show that the canyons are filled with a non-polar poorly hydrated material, similar to that observed in pig skin stratum corneum. These results together with the data obtained from skin autofluorescence images suggest that these canyons are invaginations/extension of SC material. Fluorescently labeled lipids incorporated into very flexible liposomes are able to penetrate into the skin, eventually reaching the basal layer and the dermis plane. The presence of charged lipids in the liposomes enhances size stability and thus the efficiency of penetration.

Simulations of skin barrier function: free energies of hydrophobic and hydrophilic transmembrane pores in ceramide bilayers

Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO) weaken the barrier function of the skin. We have used the potential of mean constraint force (PMCF) method to calculate the free energy of pore formation in ceramide bilayers in both the innate gel phase and in the DMSO-induced fluidized state. Our simulations show that the fluid phase bilayers form archetypal water-filled hydrophilic pores similar to those observed in phospholipid bilayers. In contrast, the rigid gel-phase bilayers develop hydrophobic pores. At the relatively small pore diameters studied here, the hydrophobic pores are empty rather than filled with bulk water, suggesting that they do not compromise the barrier function of ceramide membranes. A phenomenological analysis suggests that these vapor pores are stable, below a critical radius, because the penalty of creating water-vapor and tail-vapor interfaces is lower than that of directly exposing the strongly hydrophobic tails to water. The PMCF free energy profile of the vapor pore supports this analysis. The simulations indicate that high DMSO concentrations drastically impair the barrier function of the skin by strongly reducing the free energy required for pore opening.

Double emulsion templated monodisperse phospholipid vesicles

We present a novel approach for fabricating monodisperse phospholipid vesicles with high encapsulation efficiency using controlled double emulsions as templates. Glass-capillary microfluidics is used to generate monodisperse double emulsion templates. We show that the high uniformity in size and shape of the templates are maintained in the final phospholipid vesicles after a solvent removal step. Our simple and versatile technique is applicable to a wide range of phospholipids.

In vitro percutaneous permeation and skin accumulation of finasteride using vesicular ethosomal carriers

In order to develop a novel transdermal drug delivery system that facilitates the skin permeation of finasteride encapsulated in novel lipid-based vesicular carriers (ethosomes)finasteride ethosomes were constructed and the morphological characteristics were studied by transmission electron microscopy. The particle size, zeta potential and the entrapment capacity of ethosome were also determined. In contrast to liposomes ethosomes were of more condensed vesicular structure and they were found to be oppositely charged. Ethosomes were found to be more efficient delivery carriers with high encapsulation capacities. In vitro percutaneous permeation experiments demonstrated that the permeation of finasteride through human cadaver skin was significantly increased when ethosomes were used. The finasteride transdermal fluxes from ethosomes containing formulation (1.34 +/- 0.11 microg/cm(2)/h) were 7.4, 3.2 and 2.6 times higher than that of finasteride from aqueous solution, conventional liposomes and hydroethanolic solution respectively (P < 0.01).Furthermore, ethosomes produced a significant (P < 0.01) finasteride accumulation in the skin, especially in deeper layers, for instance in dermis it reached to 18.2 +/- 1.8 microg/cm(2). In contrast, the accumulation of finasteride in the dermis was only 2.8 +/- 1.3 microg/cm(2) with liposome formulation. The study demonstrated that ethosomes are promising vesicular carriers for enhancing percutaneous absorption of finasteride.

Percutaneous absorption of interferon-alpha by self-dissolving micropiles

To ascertain the pharmaceutical usefulness of self-dissolving micropiles (SDMPs) containing interferon (IFN), two types of SDMPs were prepared using chondroitin sulfate and dextran as the base. After percutaneous administration of 5000 IU/kg IFN-alpha2b SDMP to rats, serum IFN levels were measured for 6 h. The peak serum IFN level, maximum drug concentration (Cmax), and the time when serum IFN level reaches to Cmax, time to reach maximum concentration (Tmax), were 8.2+/-0.5 IU/ml and 1.2+/-0.1 h, respectively, for chondroitin SDMP. For dextran SDMP, Cmax and Tmax were 3.1+/-0.4 IU/ml and 3.3+/-0.3 h, respectively. AUC of chondroitin SDMP was 1.5 times greater than that of dextran SDMP. Bioavailabilities (BAs) of IFN were 378.3% for chondroitin SDMP and 255.9% for dextran SDMP that were larger than 100%. The BA of IFN from subcutaneous (s.c.) injection solution was 320.9%. The relative BAs of IFN SDMPs against s.c. injection solution were 117.8% for chondroitin SDMP and 79.9% dextran SDMP. An in vitro release experiment suggested the faster release rate of IFN from chondroitin SDMP, 57.3% at 5 min, than dextran SDMP, 32.6% at 5 min. Chondroitin SDMP containing IFN showed good stability for 3 months and no damage to the administered rat skin.

Antihyperglycemic effect of insulin from self-dissolving micropiles in dogs

As a percutaneous delivery device, self-dissolving micropiles (SDMPs) composed of chondroitin sulfate and insulin were prepared under room temperature from highly concentrated solution, glue. The mean weight of SDMP was 1.03+/-0.04 mg. One insulin SDMP was percutaneously administered to the shaved abdominal skin of four beagle dogs at insulin dose level of 1.0 and 2.0 IU/dog. After administration, blood samples were collected for 6 h and plasma glucose levels were measured. The time when minimum plasma glucose level appeared, T(min), was 1.38+/-0.2 h for 1.0 IU study and 1.38+/-0.1 h for 2.0 IU study and clear dose-dependent hypoglycemic effect of insulin was observed in the dose range. By comparing the area above the plasma glucose level vs. time curve (AAC) between insulin SDMP and subcutaneous (s.c.) injection solution, the relative pharmacological availabilities were 99% (1.0 IU) and 90% (2.0 IU), respectively. To ascertain the usefulness of insulin SDMP, oral glucose tolerance test (OGTT) was performed. When dogs were treated with insulin SDMPs, 2.0 IU, followed by an OGTT 30 min, glycemia did not appear for 5 h. On the other hand, when OGTT was performed at 1 h after insulin SDMP administration, hypoglycemia appeared as in the case of s.c. injection of insulin solution, 2.0 IU. Insulin SDMP improved the oral glucose challenge for 3 h, with a maximum effect at 30 min before the administration of glucose. Those results suggest the usefulness of a SDMP for the percutaneous delivery of peptide/protein drugs like insulin.

Novel method for stratum corneum pore size determination using positron annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy (PALS) is a powerful tool for the investigation of microstructure. Three main classes of materials, metals, semiconductors and polymers, have been studied by using this technique. But, relatively few investigations have been performed in the biological sciences. PALS provides important information on pore properties and free volume at the molecular level. Our PALS study showed that Yucatan miniature pig stratum corneum separated with heat and trypsin digestion had a longer positron annihilation lifetime than cyclodextrins. This indicates that the stratum corneum has larger pores and/or free volume than cyclodextrins, whose pores have a diameter of 0.5-0.8 nm and a torus height of 0.79 nm. Positron annihilation spectroscopy may be developed as a new technique for the detection of nano-pore properties and free volume in the biological sciences.

Evaluation of self-dissolving needles containing low molecular weight heparin (LMWH) in rats

Feasibility study of self-dissolving needles containing polysaccharide was performed. Low molecular weight heparin (LMWH) was used as a representative polysaccharide. Using chondroitin, dextran and dextrin as the base, self-dissolving needles (SDN) were prepared. The obtained SDNs were evaluated in rat absorption experiment, where pharmacological availability (PA) was calculated by comparing the plasma anti-Xa activity vs. time curves between SDNs and i.v. solution. After the insertion of SDNs to rats skin where the doses of LMWH were 25, 50 and 100 IU/kg, plasma samples were collected for 6h and anti-Xa activity was measured as the pharmacological index of LMWH. The anti-Xa level was maintained above 0.2 IU/ml, the therapeutic level, for about 2h at a dose of 100 IU/kg. Almost the same PAs of LMWH were obtained with dextran and dextrin SDNs, 97.7% and 102.3%, though lower PA was obtained with chondroitin SDN, 81.5%. In vitro dissolution experiment showed that LMWH was released from dextran, dextrin and chondroitin SDNs within 10 min. The T(50%)s were 0.84+/-0.06 min for dextran SDN, 1.07+/-0.12 min for chondroitin SDN and 2.11+/-0.31 min for dextrin SDN, respectively. Plasma anti-Xa activity vs. time profiles showed good dose-dependency in the 25-100 IU/kg range and high PAs were obtained, 90.0% for 25 IU/kg, 95.4% for 50 IU/kg and 97.7% for 100 IU/kg from dextran SDNs. Stability experiment was performed with dextran SDNs for 3 months. Above 97% of LMWH were remained in SDNs under three different conditions, -80, 4 and 40 degrees C. These results suggest the usefulness of SDN to polysaccharide drug.

Enhanced transdermal delivery of salbutamol sulfate via ethosomes

The main objective of the present work was to compare the transdermal delivery of salbutamol sulfate (SS), a hydrophilic drug used as a bronchodilator, from ethosomes and classic liposomes containing different cholesterol and dicetylphosphate concentrations. All the systems were characterized for shape, particle size, and entrapment efficiency percentage, by image analysis optical microscopy or transmission electron microscopy, laser diffraction, and ultracentrifugation, respectively. In vitro drug permeation via a synthetic semipermeable membrane or skin from newborn mice was studied in Franz diffusion cells. The selected systems were incorporated into Pluronic F 127 gels and evaluated for both drug permeation and mice skin deposition. In all systems, the presence of spherical-shaped vesicles was predominant. The vesicle size was significantly decreased (P < .05) by decreasing cholesterol concentration and increasing dicetylphosphate and ethanol concentrations. The entrapment efficiency percentage was significantly increased (P < .05) by increasing cholesterol, dicetylphosphate, and ethanol concentrations. In vitro permeation studies of the prepared gels containing the selected vesicles showed that ethosomal systems were much more efficient at delivering SS into mice skin (in terms of quantity and depth) than were liposomes or aqueous or hydroalcoholic solutions.

Enhancement of skin penetration of vitamin K using monoolein-based liquid crystalline systems

Application of vitamin K (vitK) to the skin has been used for suppression of pigmentation and resolution of bruising. However, there is no report concerning the extent of its penetration in the skin. In this study, we investigated the in vitro skin penetration and transdermal delivery of vitK, and whether these parameters may be enhanced by lipid-based drug delivery systems. The lipid formulation used in this study contains monoolein (MO), which is structured as a liquid crystalline phase, named hexagonal phase. The skin penetration of vitK was assessed in vitro using porcine ear skin mounted in a Franz diffusion cell. VitK (2.5%, w/w) was incorporated in either of three formulations: liquid vaseline, MO-based hexagonal phase gel (MO-vitK-water at 77.5/2.5/20, w/w/w) and MO-based nanodispersion of hexagonal phase (MO-vitK-poloxamer-water at 15/2.5/0.9/81.6, w/w/w/w). When vaseline was used, vitK was delivered mainly to the stratum corneum (SC): 9.50+/-0.97 microg/cm(2) of vitK was delivered to the SC at 12 h post-application, whereas 4.90 +/- 1.28 microg/cm(2) of vitK was delivered to the epidermis (E)+dermis (D) at the same time point. The hexagonal phase gel and the nanodispersion delivered approximately 2 times more vitK to the SC and 2.0-3.7 times more vitK to the [E+D] than the vaseline solution. The nanodispersion (but not the gel) also increased the transdermal delivery of vitK at 9 h ( approximately 3-fold increase). These results demonstrate that the topical delivery of vitK incorporated in a lipophilic vehicle is small, but it may be enhanced by MO-based systems, which might be useful to increase the effectiveness of topical vitK therapy.