Interaction of liquid foams with porous substrates

Foams Set a New Pace for the Release of Diclofenac Sodium

Medicated foams have emerged as promising alternatives to traditional carrier systems in pharmaceutical research. Their rapid and convenient application allows for effective treatment of extensive or hirsute areas, as well as sensitive or inflamed skin surfaces. Foams possess excellent spreading capabilities on the skin, ensuring immediate drug absorption without the need for intense rubbing. Our research focuses on the comparison of physicochemical and biopharmaceutical properties of three drug delivery systems: foam, the foam bulk liquid, and a conventional hydrogel. During the development of the composition, widely used diclofenac sodium was employed. The safety of the formulae was confirmed through an in vitro cytotoxicity assay. Subsequently, the closed Franz diffusion cell was used to determine drug release and permeation in vitro. Ex vivo Raman spectroscopy was employed to investigate the presence of diclofenac sodium in various skin layers. The obtained results of the foam were compared to the bulk liquid and to a conventional hydrogel. In terms of drug release, the foam showed a rapid release, with 80% of diclofenac released within 30 min. In summary, the investigated foam holds promising potential as an alternative to traditional dermal carrier systems, offering faster drug release and permeation.

Carbon dioxide foam bubbles enhance skin penetration through the stratum corneum layer with mechanical mechanism

Topical skin formulations often include penetration enhancers that interact with the outer stratum corneum (SC) layer to chemically enhance diffusion. Alternatively, penetration can be mechanically enhanced with simple rubbing in the presence of solid particles sometimes included to exfoliate the top layers of the SC. Our goal was to evaluate micron-sized carbon dioxide bubbles included in a foamed moisturizing formulation as a mechanical penetration enhancement strategy. We show that moisturizing foam bubbles cause an increase in SC formulation penetration using both mechanical and spectroscopic characterization. Our results suggest viscous liquid film drainage between coalescing gaseous bubbles creates local regions of increased hydrodynamic pressure in the foam liquid layer adjacent to the SC surface that enhances treatment penetration. An SC molecular diffusion model is used to rationalize the observed behavior. The findings indicate marked increased levels of treatment concentration in the SC at 2 h and that persists to 18 h after exposure, far exceeding non-foamed treatments. The study suggests an alternate strategy for increasing formulation penetration with a non-chemical mechanism.

Foam Quality of Foams Formed on Capillaries and Porous Media Systems

Foams are of great importance as a result of their expansive presence in everyday life—they are used in the food, cosmetic, and process industries, and in detergency, oil recovery, and firefighting. There is a little understanding of foam formation using soft porous media in terms of the quality of foam and foam formation. Interaction of foams with porous media has recently been investigated in a study by Arjmandi-Tash et al., where three different regimes of foam drainage in contact with porous media were observed. In this study, the amount of foam generated using porous media with surfactant solutions is investigated. The aim is to understand the quality of foam produced using porous media. The effect of capillary sizes and arrangement of porous in porous media has on the quality of foam is investigated. This is then followed by the use of soft porous media for foam formation to understand how the foam is generated on the surface of the porous media and the effect that different conditions (such as concentration) have on the quality of the foam. The quality of foam is a blanket term for bubble size, liquid volume fraction, and stability of the foam. The liquid volume fraction is calculated using a homemade dynamic foam analyser, which is used to obtain the distribution of liquid volume fraction along with the foam height. Soft porous media does not influence substantially the rate of decay of foam produced, however, it decreases the average diameter of the bubbles, whilst increasing the range of bubble sizes due to the wide range of pore sizes present in the soft porous media. The foam analyser showed the expected behaviour that, as the foam decays and becomes drier, the liquid volume fraction of the foam falls, and therefore the conductivity of foam also decreases, indicating the usefulness of the home-made device for future investigations.

Foam Formation and Interaction with Porous Media

Foams are a common occurrence in many industries and many of these applications require the foam to interact with porous materials. For the first time interaction of foams with porous media has been investigated both experimentally and theoretically by O. Arjmandi-Tash et al. It was found that there are three different regimes of the drainage process for foams in contact with porous media: rapid, intermediate and slow imbibition. Foam formation using soft porous media has only been investigated recently, the foam was made using a compression device with soft porous media containing surfactant solution. During the investigation, it was found that the maximum amount of foam is produced when the concentration of the foaming agent (dishwashing surfactant) is in the range of 60–80% m/m. The amount of foam produced was independent of the pore size of the media in the investigated range of pore sizes. This study is expanded using sodium dodecyl sulphate (SDS), which has the same critical micelle concentration as the commercial dishwashing surfactant, where the foam is formed using the same porous media and compression device. During the investigation, it was found that 10 times the critical micelle concentration (CMC) is the optimum concentration for a pure SDS surfactant solution to create foam. Any further increase in concentration after that point resulted in no further mass of foam being generated.