Effect of charge and lipid concentration on in-vivo percutaneous absorption of methyl nicotinate from liposomal vesicles

The technology of transdermal delivery nanosystems: from design and development to preclinical studies

Transdermal administration has gained much attention due to the remarkable advantages such as patient compliance, drug escape from first-pass elimination, favorable pharmacokinetic profile and prolonged release properties. However, the major limitation of these systems is the limited skin penetration of the stratum corneum, the skin's most important barrier, which protects the body from the insertion of substances from the environment. Transdermal drug delivery systems are aiming to the disruption of the stratum corneum in order for the active pharmaceutical ingredients to enter successfully the circulation. Therefore, nanoparticles are holding a great promise because they can act as effective penetration enhancers due to their small size and other physicochemical properties that will be analyzed thoroughly in this report. Apart from the investigation of the physicochemical parameters, a comparison between the different types of nanoparticles will be performed. The complexity of skin anatomy and the unclear mechanisms of penetration should be taken into consideration to reach some realistic conclusions regarding the way that the described parameters affect the skin permeability. To the best of the authors knowledge, this is among the few reports on the literature describing the technology of transdermal delivery systems and how this technology affects the biological activity.

Preparation, characterization, and in vivo evaluation of cyclosporine cationic liposomes for the treatment of psoriasis

Cyclosporine (CYC), a calcineurin inhibitor acts specifically on T-cells and is one of the most effective treatment options for psoriasis. Systemic administration of the drug has been associated with dose-dependent toxic effects, while its topical delivery is a challenging task due to unfavourable physicochemical properties of drug. The aim of the present study is to develop and evaluate the efficacy of topical liposomal gel containing CYC loaded cationic liposomal nanocarriers in imiquimod induced psoriatic plaque model. Liposomes composed of DOTAP and cholesterol was formulated by different liposomal preparation techniques. Optimized liposomal carriers prepared by ethanol injection method were characterized with respect to size, zeta potential, entrapment efficiency, stability, in vitro drug release and in vivo studies. Cationic liposomes with particle size of 111 ± 1.62 nm, PDI of 0.27 ± 0.08, entrapment efficiency of 93 ± 2.12%, and zeta potential of 41.12 ± 3.56 mV were obtained. Drug loaded liposomal gels showed shear thinning behaviour, which is suitable for topical application. Topical application of CYC liposomal gels on imiquimod induced psoriatic plaque model reduced the symptoms of psoriasis and levels of key psoriatic cytokines such as tumour necrosis factor-α, IL-17, and IL-22. In conclusion, the developed liposomal carrier of CYC was found to be effective and can find application in treatment of psoriasis.

Evaluation of percutaneous absorption of naproxen from different liposomal formulations

The present study concerns the percutaneous absorption of naproxen (NPX), as model anti-inflammatory drug, included in liposome formulations constituted of different lipids: stratum corneum lipids (SCL) and phosphatidylcholine/cholesterol (PC/CHOL). Liposome dispersions were produced using two different methods: reverse-phase evaporation (REV) and thin layer evaporation (TLE). Morphology and dimensions of the disperse phase were characterized by cryo-transmission electron microscopy (cryo-TEM) and photon correlation spectroscopy, respectively. X-ray diffraction was employed to determine the structural organization of the vesicles. In vitro diffusion was studied by Franz cell on liposome dispersions viscosized by carbomer. Tape stripping was performed to investigate in vivo the performance of differently composed liposomes as NPX delivery system. Cryo-TEM showed spherical vesicles and bigger irregular elongated nanoparticles for TLE SCL liposomes. REV resulted in spherical and elongated multilamellar vesicles. Also X-ray diffraction evidenced L alpha or L beta multilamellar vesicles for PC/CHOL and SCL liposome respectively. The in vitro study showed a lower NPX flux for SCL with respect to PC/CHOL liposome. Tape stripping corroborate the in vitro findings regarding SCL, suggesting that liposomes create a drug reservoir mixing with SC lipids, whilst PC/CHOL liposome promoted NPX permeation through the skin. Liposome lipid composition seems to affect NPX permeation through the skin.

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.