Topical Lipid Based Drug Delivery Systems for Skin Diseases: A Review

Treatment of skin ailments through systemic administration is limited due to toxicity and patients discomfort. Hence, lower risk of systemic side effects from topical dosage forms like ointments, creams, emulsions and gels is more preferred for the treatment of skin disease. Application of lipid based carriers in drug delivery in topical formulations has recently become one of the major approaches to improve drug permeation, safety, and effectiveness. These delivery systems include liposomes, ethosomes, transfersomes, Nanoemulsions (NEs), Solid Lipid Nanoparticles (SLNs) Nanostructured Lipid Carriers (NLCs) and micelles. Most of the liposomes and SLNs based products are in the market while some are under investigation. Transcutaneous delivery of therapeutics to the skin layer by novel lipid based carriers has enhanced topical therapy for the treatment of skin ailments. This article covers an overview of the lipid-based carriers for topical uses to alleviate skin diseases.

Effective Transcutaneous Delivery of Hyaluronic Acid Using an Easy-to-Prepare Reverse Micelle Formulation

The skin loses its moisture with advancing age, causing cosmetic issues such as wrinkles. In addition, the loss of moisture leads to hypersensitivity to external stimuli such as UV light. Transcutaneous supplementation with hyaluronic acid (HA) is an effective and safe method of recovering the moisturizing function and elasticity of the skin. However, the transcutaneous delivery of HA remains challenging owing to the barrier function of the stratum corneum (SC) layer. To penetrate the SC barrier, we used a reverse micelle formulation that does not require high energy consumption processes for preparation. We aimed to enhance the skin permeability of HA by incorporating glyceryl monooleate—a skin permeation enhancer—into the formulation. A fluorescently-labeled HA-loaded reverse micelle formulation showed significantly enhanced permeation across Yucatan micro pig skin. Fourier transform infra-red spectroscopy of the surface of the skin treated with the reverse micelle formulation showed blue shifts of the CH2 symmetric/asymmetric stretching peaks, indicating a reduction in the barrier function of the SC. Further study revealed that HA was released from the reverse micelles at the hydrophobic/hydrophilic interface between the SC and the living epidermis. The results demonstrated that our reverse micellar system is an easy-to-prepare formulation for the effective transcutaneous delivery of HA.

In Vivo Experimental Study on the Enhancement of Optical Clearing Effect by Laser Irradiation in Conjunction with a Chemical Penetration Enhancer

The penetration of optical clearing agents (OCAs) is restricted by the natural barrier function of the stratum corneum (SC) of the skin, which can be breached by physical and chemical methods to enhance the transcutaneous delivery of OCAs. To breach the barrier function of SC, we carried out the in vivo experimental study to enhance the optical clearing effect of PEG-400 by laser irradiation in conjunction with a chemical penetration enhancer thiazone. We compared the reflectance spectra of skin without laser irradiation or thiazone. Mono-treatment of thiazone could not significantly enhance the optical clearing efficacy of the skin. After 60 min, the reflectance spectrum decreased by only approximately 10%. With the combined treatment, the reflectance spectrum decreased by approximately 30% after 10 min. Subsequently, the effect of laser dose on the enhancement of optical clearing efficacy was studied. The optimal irradiation dose was determined. The reflectance of skins irradiated by a laser dose at 0.7 J/cm2 decreased by approximately 10% and were 20% lower than those at 0.5 and 0.9 J/cm2. The laser at 0.5 J/cm2 could not damage the SC completely, whereas the laser at 0.9 J/cm2 influenced the epidermis and dermis; thus, the reflectance of skin samples irradiated by 0.9 J/cm2 did not decrease.