Current progress and future prospects of liposomes in dermal drug delivery

Nanodermatology-based solutions for psoriasis: State-of-the art and future prospects

Nanodermatology is an emerging, multidisciplinary science, arising from the convergence of nanotechnology, pharmacology, physics/biophysics, chemistry/biochemistry, chemical engineering, material science, and clinical medicine. Nanodermatology deals with (a) skin biology, anatomy, and physiology at the nanoscale ("skin nanobiology"), (b) diagnosis performed by means of novel diagnostic devices, assisted by nanobiotechnologies ("nanodiagnosis"), and (c) treatment through innovative therapeutic agents, including phototherapy ("photonanotherapy"/"photonanodermatology") and systemic/topical drug administration ("nanotherapy") at the nanoscale, and drug delivery-such as transdermal or dermal drug delivery (TDDD/DDD)-enhanced and improved by nanostructures and nanodrugs ("nanodrug delivery"). Nanodermatology, as a super-specialized branch of dermatology, is a quite recent specialty: the "Nanodermatology Society" founded by the eminent dermatologist Dr. Adnan Nasir, was established in 2010, with the aim of bringing together different stakeholders, including dermatologists, nanotechnology scientists, policy-makers and regulators, as well as students and medical residents. Psoriasis has a prevalence of 2-3% worldwide and imposes a severe clinical and societal burden. Nanodermatology-based solutions appear promising for the proper treatment and management of psoriasis, assisting and enhancing different steps of the process of health-care delivery: from the diagnosis to the therapeutics, paving the way for a personalized approach, based on the specific dysregulated biomarkers.

Enhanced topical delivery of tetrandrine by ethosomes for treatment of arthritis

The purpose of this work was to explore the feasibility of ethosomes for improving the antiarthritic efficacy of tetrandrine by topical application. It was found that tetrandrine was a weak base (pK(a) = 7.06) with pH-dependent partition coefficient. The spherical-shaped ethosomes were prepared by pH gradient loading method. Ex vivo permeation and deposition behavior demonstrated that the drug flux across rat skin and deposition of the drug in rat skin for ethosomes was 2.1- and 1.7-fold higher than that of liposomes, respectively. Confocal laser scanning microscopy confirmed that ethosomes could enhance the topical delivery of the drug in terms of depth and quantity compared with liposomes. The ethosomes were shown to generate substantial enhancement of therapeutic efficacy of tetrandrine on Freund's complete adjuvant-induced arthritis with regard to liposomes. These results indicated that ethosomes would be a promising carrier for topical delivery of tetrandrine into and across the skin.

Topical drug delivery by a polymeric nanosphere gel: Formulation optimization and in vitro and in vivo skin distribution studies

Tyrosine-derived nanospheres have demonstrated potential as effective carriers for the topical delivery of lipophilic molecules. In this investigation, a gel formulation containing nanospheres was developed for effective skin application and enhanced permeation. Carbopol and HPMC hydrophilic gels were evaluated for dispersion of these nanospheres. Sparingly water soluble diclofenac sodium (DS) and lipophilic Nile Red were used as model compounds. DS was used to determine the optimum polymer type, viscosity and release properties of the gel while fluorescent Nile Red was used in in vitro and in vivo skin distribution studies. In addition, the effect of a penetration enhancer, Azone, on the skin delivery was investigated. Dispersion of Nile Red-loaded nanospheres in 1% w/v HPMC gel produced a uniform and stable dispersion with suitable rheological properties for topical application, without any short-term cellular toxicity or tissue irritation. In vitro permeation studies using human cadaver skin revealed that the deposition of Nile Red via the nanosphere gel in the upper and lower dermis was 1.4 and 1.8 fold higher, respectively, than the amount of Nile Red deposited via an aqueous nanosphere formulation. In vivo, the HPMC gel containing Nile Red-loaded nanospheres significantly enhanced (1.4 fold) the permeation of Nile Red to the porcine stratum corneum/epidermis compared to the aqueous Nile Red-loaded nanospheres. An additional increase (1.4 fold) of Nile Red deposition in porcine stratum corneum/epidermis was achieved by incorporation of Azone (0.2M) into the nanosphere gel formulation. Therefore, tyrosine-derived nanospheres dispersed in gels offer promise for the topical delivery of lipophilic drugs and personal care agents to skin for treatment of cancers, psoriasis, eczema, and microbial infections.

A comparison of the skin permeation of three topical 0.5% fluorouracil formulations with that of a 5% formulation

BACKGROUND

Topical fluorouracil has proven efficacy in the treatment of actinic keratosis. The systemic absorption of various topical formulations of fluorouracil varies, however, and may be affected by the concentration and delivery system used.

OBJECTIVE

This study compared the flux and percutaneous absorption of 3H-labeled fluorouracil from three 0.5% fluorouracil formulations incorporated into a porous microsphere delivery system with those from a commercially available 5% fluorouracil formulation.

METHODS

Penetration of all formulations through the skin was sampled every 3 hours for 24 hours using full-thickness human cadaver skin samples mounted in a Bronaugh flow-through diffusion cell apparatus. Total absorption was defined as the sum of the amount of cumulative flux through the skin over 24 hours and the amount retained in the skin at 24 hours.

RESULTS

The flux through the skin of the 5% fluorouracil formulation was 20 to 40 times greater (normalized, 2-4 times greater) than that of the 0.5% fluorouracil formulations. A higher percentage of absorbed fluorouracil was retained in the skin after 24 hours with the 0.5% formulations (86%-92%) than with the 5% formulation (54%).

CONCLUSION

These findings suggest that the 0.5% formulations are associated with less flux through the skin than the 5% formulation and, therefore, potentially less systemic exposure.

Interaction of liposomes with human skin in vitro--the influence of lipid composition and structure

Liposomes have been suggested as a vehicle for dermal and transdermal drug delivery, but the knowledge about the interaction between lipid vesicles and human skin is poor. Therefore, we visualized liposome penetration into the human skin by confocal laser scanning microscopy (CLSM) in vitro. Liposomes were prepared from phospholipids in different compositions and labeled with a fluorescent lipid bilayer marker, N-Rh-PE (L-alpha-phosphatidylethanolamine-N-lissamine rhodamine B sulfonyl). Fluorescently labelled liposomes were not able to penetrate into the granular layers of epidermis. However, the fluorescence from liposome compositions containing DOPE (dioleylphosphatidyl ethanolamine) was able to penetrate deeper into the stratum corneum than that from liposomes without DOPE. Pretreatment of skin with unlabeled liposomes containing DOPE or lyso-phosphatidyl choline (lyso-PC) enhanced the subsequent penetration of the fluorescent markers, N-Rh-PE and sulforhodamine B into the skin, suggesting possible enhancer activity, while most liposomes did not show such enhancement. Resonance energy transfer (RET) and calcein release assay between stratum corneum lipid liposomes (SCLLs) and the phospholipid vesicles suggested that the liposomes containing DOPE may fuse or mix with skin lipids in vitro and loosen the SCLL bilayers, respectively. Among the factors not affecting stratum corneum penetration were: negative charge, cholesterol inclusion and acyl chain length of the phospholipids. In conclusion, fusogenicity of the liposome composition appears to be a prerequisite for the skin penetration.

Submicron emulsion vehicle for enhanced transdermal delivery of steroidal and nonsteroidal antiinflammatory drugs

Significant improvement is demonstrated for transdermal delivery of steroidal and nonsteroidal antiinflammatory drugs (NSAID), including betamethasone valerate and dipropionate, indomethacin, diclofenac, piroxicam, and naproxen, when formulated in a submicron Emulsion (SME) vehicle rather than in standard creams. SMEs comprise oil droplets, with mean size of approximately 100 nm (0.1 micron), dispersed in a continuous water phase. Hydrophobic drugs are incorporated into the oil phase of the SME, resulting in improved penetration and increased efficacy of the incorporated antiinflammatory drug. The performance of medicated topical SME was compared with that of regular topical cream formulations, as measured by the carrageenan-induced paw edema rat model. Indomethacin in SME topical vehicle was 50% more active than in regular cream base, Diclofenac in SME proved to be 40% more active than Voltaren Emulgel. Improvement of steroidal antiinflammatory drugs action in topical SME cream was even more pronounced; that is, up to 3-4-fold. Antiinflammatory drugs in SME also demonstrate noticeable systemic activity, but for regional edema treatment, local delivery is advantageous. The new SME delivery system was tested for primary irritation in humans in a 48-h trial. Low irritancy and excellent human acceptance for SME placebo or diclofenac-loaded SME cream make this novel transdermal/topical DDS attractive for further development.