Phase equilibrium, dynamics and rheology of phospholipid-ethanol mixtures: a combined molecular dynamics, NMR and viscometry study.

Binary mixtures of ethanol and phospholipids DOPC and DOPE have been investigated in a composition range relevant for topical drug delivery applications. This was done using a combined computer simulation and experimental approach where molecular dynamics simulations of ethanol-lipid mixtures with different compositions were performed. Several key properties including diffusion coefficients, longitudinal relaxation times, and shear viscosity were computed. In addition, diffusion coefficients, viscosities and NMR longitudinal relaxation times were measured experimentally for comparison and in order to validate the results from simulation. Diffusion coefficients and relaxation times obtained from simulations are in good agreement with results from NMR and computed viscosities are in reasonable agreement with viscometry experiments indicating that the simulations provide a realistic description of the ethanol-phospholipid mixtures. Structural changes in the simulated systems were investigated using an analysis based on radial distribution functions. This showed that the structure of ethanol-DOPC mixtures remains essentially unchanged in the investigated concentration range while ethanol-DOPE mixtures undergo structural rearrangements with the tendency for forming small aggregates on the 100 ns time scale consisting of less than 10 lipids. Although our simulations and experiments indicate that no larger aggregates form, they also show that DOPE has stronger aggregation tendency than DOPC. This highlights the importance of the character of the lipid headgroup for lipid aggregation in ethanol and gives new insights into phase equilibrium, dynamics and rheology that could be valuable for the development of advanced topical drug delivery formulations.

Efficacy and Safety of Water-Free Lipid Formulation System Containing Calcipotriol Against Psoriasis Vulgaris.

Calcipotriol, a vitamin D analogue is widely used in the treatment of psoriasis. However, poor adherence to topical therapy has led to an ineffective use of the medication and built a barrier to the treatment's success. A water-free lipid-based formulation system has been developed to improve dosage and cosmetic properties along with patient compliance. This study was conducted to evaluate the efficacy and cutaneous safety of water-free lipid-based formulations containing calcipotriol (50 μg/g) as compared to their corresponding vehicles and marketed calcipotriol formulations in a psoriasis plaque test. In total, 24 subjects with chronic psoriasis vulgaris were enrolled in this single-center, randomized, vehicle, and comparator-controlled clinical trial and treated once daily over a 12-day period (10 applications). The anti-psoriatic effect was evaluated by sonographic measurement of psoriatic infiltrate and investigators' clinical efficacy assessments. The mean reduction in psoriatic infiltrate from baseline to day 12 (end of trial) with lipid-based calcipotriol formulations (-34% and -37%) was statistically significant (P<0.0001) when compared to their corresponding vehicles (6% and -4%) but not when compared with marketed calcipotriol solution and cream (-34% and -49% respectively). Mean total clinical assessment scores of these lipid-based calcipotriol formulations (1.7 each) were between those of the two comparators - greater than marketed calcipotriol solution (1.3) but lower than cream (2.0). Overall, nine mild non-serious treatment-emergent adverse effects related to all calcipotriol formulations were reported in four subjects, but all recovered at the follow-up visit. Therefore, novel lipid-based formulations of calcipotriol were clearly more efficacious than their corresponding vehicles and considered as safe therapy against psoriasis vulgaris. J Drugs Dermatol. 2023;22(2):197-202. doi:10.36849/JDD.7151Citation: Holmbäck J, Carlsson A, Rinwa P. Efficacy and safety of water-free lipid formulation system containing calcipotriol against psoriasis vulgaris. J Drugs Dermatol. 2023;22(2):197-202. doi:10.36849/JDD.7151  .

Sorptive Capacities of Nonpolymeric Plant Lipids for Hydrophobic Chemicals Determined by Passive Dosing.

Vegetation plays an important role in the partitioning, transport, and fate of semivolatile hydrophobic organic chemicals (HOCs) in the environment. Leaf/air partition ratios ( Kleaf/air) of HOCs are highly variable for different plant species. The differences cannot be fully explained by the fraction of lipids in the leaves or the thickness of the cuticle. Our goal was to elucidate the importance of nonpolymeric lipids in determining Kleaf/air. To do this, we extracted organic matter from 7 plant species using solvents that do not extract the polymeric lipids cutin and cutan, to yield extractable organic matter (EOM). We used passive dosing to determine the partition ratios of selected HOCs between the EOM of the leaves and our reference lipid, olive oil ( KEOM/olive oil). In addition, we measured analogous partition ratios for three lipid standards. Proton nuclear magnetic resonance (NMR) spectroscopy was used to characterize the composition of lipids. Differences in KEOM/olive oil of two polychlorinated biphenyls and four chlorinated benzenes were below a factor of 2 in the plant species studied, indicating that the reported differences in Kleaf/air are not caused by differences in the sorptive capacities of nonpolymeric lipids or that our EOM is not representative of all nonpolymeric leaf lipids.

AKVANO®: A Novel Lipid Formulation System for Topical Drug Delivery-In Vitro Studies.

A novel formulation technology called AKVANO® has been developed with the aim to provide a tuneable and versatile drug delivery system for topical administration. The vehicle is based on a water-free lipid formulation where selected lipids, mainly phospholipids rich in phosphatidylcholine, are dissolved in a volatile solvent, such as ethanol. With the aim of describing the basic properties of the system, the following physicochemical methods were used: viscometry, dynamic light scattering, NMR diffusometry, and atomic force microscopy. AKVANO formulations are non-viscous, with virtually no or very minute aggregates formed, and when applied to the skin, e.g., by spraying, a thin film consisting of lipid bilayer structures is formed. Standardized in vitro microbiological and irritation tests show that AKVANO formulations meet criteria for antibacterial, antifungal, and antiviral activities and, at the same time, are being investigated as a non-irritant to the skin and eye. The ethanol content in AKVANO facilitates incorporation of many active pharmaceutical ingredients (>80 successfully tested) and the phospholipids seem to act as a solubilizer in the formulation. In vitro skin permeation experiments using Strat-M® membranes have shown that AKVANO formulations can be designed to alter the penetration of active ingredients by changing the lipid composition.

Preclinical development of sodium fusidate antibiotic cutaneous spray based on water-free lipid formulation system.

Topical antibiotics are a key component in the management of mild to moderate skin and soft tissue infections. There are, however, concerns about the emerging bacterial resistance against topical antibacterial agents such as fusidic acid, due to the prolonged treatment period of its marketed dosage forms. Improving the efficacy of topical formulations could potentially shorten the treatment period and avoid the resistance growth. To provide a more effective drug delivery, a water-free lipid-based formulation system (AKVANO®) which can be applied by spraying, has been developed. In the current paper, different formulations containing sodium fusidate were evaluated for their in vitro skin permeability using artificial skin mimicking membranes and antibacterial properties using ex vivo and in vivo skin wound infection models. The novel formulations containing sodium fusidate showed a much higher skin permeation (up to 60% of nominal amount) than the commercially available Fucidin® cream (3%). These formulations also gave a significantly stronger antibacterial effect than Fucidin cream showing a clear dose-response relationship for the sodium fusidate content. A spray product based on the described formulation technology would therefore require a shorter treatment time and thereby lower the risk for the development of bacterial resistance. Spray administration of these formulations provides an even layer on the skin surface from which the solvent quickly evaporates and thereby facilitates a non-touch application where no rubbing is required.

Chemicals from textiles to skin: an in vitro permeation study of benzothiazole.

Despite the possible impact on human health, few studies have been conducted to assess the penetration and accumulation of contaminants in the skin after a prolonged contact with textile materials. In previous studies, we have shown that benzothiazole and its derivatives, as well as other potentially hazardous chemicals, often are present as textile contaminants in clothes available on the retail market. Since benzothiazole is a common contaminant in clothes, these can be a possible route for human chemical exposure, both systemic and onto the skin. To investigate this potential exposure, Franz-type and flow-through cells were used for the permeation studies together with a Strat-M® artificial membranes. Experiments were performed using solutions of benzothiazole, as well as contaminated textile samples in the donor chamber. Benzothiazole was demonstrated to penetrate through, as well as being accumulated in the membrane mimicking the skin. After 24 h, up to 62% of benzothiazole was found in the acceptor cell, while up to 37% was found absorbed in the skin mimicking membrane. It also was shown that there was release and permeation from contaminated fabrics. The results indicate that benzothiazole can be released from textile materials, penetrate through the skin, and further enter the human body. This will possibly also apply to other chemical contaminants in textiles, and the results of this study indicate that the presence of these textile contaminants entails potential health risks. A rough risk assessment was made for clothing textiles according to Environmental Protection Agency (EPA) and European regulations for carcinogenic and non-carcinogenic compounds, using literature data for benzothiazole.

A single step reversed-phase high performance liquid chromatography separation of polar and non-polar lipids.

This paper reports a simple chromatographic system to separate lipids classes as well as their molecular species. By the use of phenyl coated silica as stationary phase in combination with a simple mobile phase consisting of methanol and water, all tested lipid classes elute within 30 min. Furthermore, a method to accurately predict retention times of specific lipid components for this type of chromatography is presented. Common detection systems were used, namely evaporative light scattering detection (ELSD), charged aerosol detection (CAD), electrospray mass spectrometry (ESI-MS), and UV detection.

Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - a prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates.

The retention characteristics of the major lipid components in biodiesels and edible oils as well as representative polycyclic aromatic compounds (PAHs) have been investigated on five different normal phase HPLC stationary phases, in order to optimize class separation for an automatized online HPLC cleanup of PAHs prior GC-MS analysis. By stepwise comparison of different hexane/MTBE compositions as mobile phases on cyano-, phenyl-, pentabromobenzyl-, nitrophenyl- and amino-modified silica columns, the capacity and selectivity factors for each analyte and column could be calculated. It was concluded that the most suitable column for backflush isolation of PAHs in biodiesel and edible oil matrices was the pentabromobenzyl-modified silica (PBB). A previously described online HPLC-GC-MS system using the PBB column was then evaluated by qualitative and quantitative analysis of a biodiesel exhaust particulate extract and a vegetable oil reference material. The GC-MS full scan analysis of the biodiesel particulate extract showed that the lipids had been removed from the sample and a fraction containing PAHs and oxygenated derivatives thereof had been isolated. Quantified mass fractions of PAHs of the reference material BCR-458 agreed well for most of the certified PAH mass fractions in the spiked coconut oil reference material.

Separation of lipid classes by HPLC on a cyanopropyl column.

A new method for the separation and identification of lipid classes by normal-phase HPLC on a cyanopropyl column is described. The use of a simple binary gradient, with toluene as a component, provided a rapid separation of non-polar as well as phospholipid classes. The inherent small differences in performances between possible non-polar eluent components of the gradient, such as hexane, heptane, and iso-octane, had a pronounced impact on retention times for individual phospholipid classes. Separation of molecular species within a lipid class could also be observed.