Sodium Cholate-Mediated Ion-Pairing for Skin Delivery of Methylene Blue: Physicochemical Characterization and Influence on Skin Barrier and Skin Penetration

Methylene blue (MB)-based photodynamic therapy has proven to be effective and promising for the treatment of non-melanoma skin neoplasms. However, the topical application of MB has certain challenges. MB is a cationic and water-soluble molecule. These properties limit its partition and diffusion through the layers of the skin, limiting it from reaching the neoplastic cells at therapeutic concentration. Sodium cholate (CNa), a bile salt, enables ion-pairing with cationic drugs, such as MB, through electrostatic interactions. The complex formed modifies the physicochemical properties of MB, which may enable its partition and diffusion through the layers of the skin. Thus, we proposed to investigate the interaction between CNa and MB as a function of CNa concentration and its effect on the partition coefficient, solubility, skin barrier and skin delivery of MB. Spectroscopic and thermal studies of MB/CNa dispersions suggest intermolecular interactions between MB and CNa. CNa causes an increase in the partition coefficient of MB and reduces its solubility in water. CNa at the concentrations used does not cause significant changes in electrical resistance or the profile of FTIR spectra related to the lipids and the proteins of the stratum corneum. The use of CNa at the critical micelle concentration causes a reduction in the release and cutaneous delivery of MB; and, at a concentration below the critical micelle concentration, it does not significantly influence the release, but promotes the cutaneous delivery of MB.

Monoolein-based nanodispersions for cutaneous co-delivery of methylene blue and metformin: Thermal and structural characterization and effects on the cutaneous barrier, skin penetration and cytotoxicity

This study evaluated the potential of monoolein (MO)-based nanodispersions to promote the cutaneous co-delivery of metformin (MET) and methylene blue (MB) for the treatment of non-melanoma skin cancer. MO-based nanodispersions were obtained using Kolliphor® P407 (KP) and/or sodium cholate (CH), and characterized concerning the structure, thermal stability, ability to disrupt the skin barrier, cutaneous permeation and retention of MB and MET. Additionally, the cytotoxic effect of MO nanodispersions-mediated combination therapy using MET and MB in A431 cells was evaluated. The nanodispersions exhibited nanometric size (<200 nm) and thermal and physical stability. Small angle X-ray scattering studies revealed multiple structures depending on composition. They were able to interact with stratum corneum lipid structure, increasing its fluidity. The effect of MO-nanodispersions on topical/transdermal delivery of MB and MET was composition-dependent. Nanodispersions with low MO content (5 %) and stabilized with KP and CH (0.05-0.10 %) were the most promising, enhancing the cutaneous delivery of MB and MET by 1.9 to 2.2-fold and 1.4 to 1.7-fold, respectively, compared to control. Cytotoxic studies revealed that the most promising MO nanodispersion-mediated combination therapy using MET and MB (1:1) reduced the IC₅₀ by 24-fold, compared to MB solution, and a further reduction (1.5-fold) was observed by MB photoactivation.

Human skin models: From healthy to disease-mimetic systems; characteristics and applications

Skin drug delivery is an emerging route in drug development, leading to an urgent need to understand the behaviour of active pharmaceutical ingredients within the skin. Given, As one of the body's first natural defences, the barrier properties of skin provide an obstacle to the successful outcome of any skin drug therapy. To elucidate the mechanisms underlying this barrier, reductionist strategies have designed several models with different levels of complexity, using non-biological and biological components. Besides the detail of information and resemblance to human skin in vivo, offered by each in vitro model, the technical and economic efforts involved must also be considered when selecting the most suitable model. This review provides an outline of the commonly used skin models, including healthy and diseased conditions, in-house developed and commercialized models, their advantages and limitations, and an overview of the new trends in skin-engineered models.

Transdermal delivery of tadalafil using a novel formulation

The aim of this work was to investigate the transdermal gel loaded with tadalafil, a practically insoluble selective phosphodiesterase-5 inhibitor (PDE5) in order to improve the solubility and bioavailability. The solubility of tadalafil in mixed solution of hydroxypropyl-β-cyclodextrin (HPCD), polyethylene glycol (PEG) 400 and tween 80 (T2 solution) was 260.8 ± 4.3 µg/mL and that of tadalafil in modified T2 (M-T2) solution, which tadalafil was dissolved in 20% (w/v) HPCD at first and then mixture solutions of PEG 400 and tween 80 were added, was increased to 344.9 ± 30.6 µg/mL. Four gel formulae were prepared, subsequently in vitro and in vivo skin permeation studies were carried out. Interestingly, tadalafil gel in M-T2 and oleic acid (OA) (F3) could promote the percutaneous absorption of tadalafil by 179.4% in vitro and increase AUC by 223% in vivo compared with tadalafil gel in the absence of M-T2 and OA (F1). Also, there was a finding that tadalafil gel in M-T2 and OA did not cause dermal irritations in an experimental animal.

Determination of nanostructure of liposomes containing two model drugs by X-ray scattering from a synchrotron source

Small-angle X-ray scattering has been employed to study how the introduction of paracetamol and acetylsalicylic acid into a liposome bilayer system affects the system's nanostructure. An X-ray scattering model, developed for multilamellar liposome systems [Pabst et al. (2000), Phys. Rev. E, 62, 4000-4009], has been used to fit the experimental data and to extract information on how structural parameters, such as the number and thickness of the bilayers of the liposomes, thickness of the water layer in between the bilayers, size and volume of the head and tail groups, are affected by the drugs and their concentration. Even though the experimental data reveal a complicated picture of the drug-bilayer interaction, they clearly show a correlation between nanostructure, drug and concentration in some aspects. The localization of the drugs in the bilayers is discussed.

Enhanced transdermal drug delivery of zaltoprofen using a novel formulation

Zaltoprofen is a non-steroidal anti-inflammatory drug (NSAID) belonging to the propionic acid class. It has strong inhibitory effects on acute and chronic inflammation. Although zaltoprofen is well tolerated orally compared to other NSAIDs, it has to be administered in three to four doses per day and was associated with ulcerogenicity, bellyache and indigestion. This makes administration of zaltoprofen unsuitable for patients with gastric ulcer and is also associated with drug interactions. Therefore, it is important to develop an alternative dosage form which is easier to administer and avoids first-pass metabolism. The transdermal route meets all the above advantages. In this study, zaltoprofen gels were prepared using carbomer with mixture solution of polyethylene glycol (PEG) 400, Tween 80 and (2-hydroxypropyl)-β-cyclodextrin (HPCD) (called as T2), subsequently oleic acid as a penetration enhancer was added. Zaltoprofen gel containing T2 and oleic acid could promote the percutaneous absorption of zaltoprofen and increase AUC by 183% compared to zaltoprofen gel without T2 and oleic acid. Also, there was a finding zaltoprofen gel containing T2 and oleic acid did not cause dermal irritations in an experimental animal.