Development of model systems for in vitro investigation of transdermal transport pathways

Abstract

Skin is a complex structured system primarily involved in Transdermal Drug Delivery (TDD). The outer stratum corneum represents the main barrier to the entrance of external molecules. Nowadays, none of the recognized methods, used for the investigation of penetration processes, is able to give a complete overview of the transport mechanisms involved. Standard protocols are based on the use of human or animal skin samples, which are difficult and expensive to obtain. Here, we present a novel experimental setup to investigate TDD by using Confocal Laser Scanning Microscopy and image analysis. The methodology is based on diffusion experiments of fluorescent‐labelled fluids (water, oil, and oil‐in‐water emulsions), in a model matrix. Using an agarose gel as model for a proof of concept, different penetration efficiencies were observed, suggesting an important role of both chemical composition and fluid microstructure on the transport mechanism. An adequate model system should be used to better mimic the stratum corneum morphology and properties. To this aim, several bicontinuous emulsion gels, obtained from an emulsification process, were preliminary formulated and suggested as model systems to mimic the stratum corneum. In this work, we define the key directions for the development of an innovative approach to study the penetration of formulations through the skin.

Experimental methods in chemical engineering: Fluorescence emission spectroscopy

“…Eng. published in 2016 and 2017 measured bubble size and velocity with endoscopic bubble image velocimetry (EBIV), where a laser excites a fluorescent dye in the liquid (blue cluster); evaluated diffusion rates of fluorescent molecules with confocal time‐lapse microscopy; verified how well fluorophores were grafted in compounds (green cluster); how well fluorescent molecule were functionalized by fluorescence spectroscopy (green cluster); monitored wastewater, by tracking cellular material and microbiological activity (blue cluster); and created a sensor for volatile organic compounds based on aggregation‐induced emission (AIE) from two‐dimensional MOFs (blue and green cluster) . Atomic fluorescence spectrometry (AFS) is an element specific technique that emits photons at the same wavelengths as the incident photons (green cluster) .…”

Issue Highlights

“…Key directions for the development of an innovative approach to study the penetration of formulations through the skin are provided. [1] 1690 Production of Menthol-Loaded Nanoparticles by Solvent Displacement Ada Ferri, Naveeta Kumari, Roberta Peila and Antonello A. BarresiMenthol-loaded poly--caprolactone nanoparticles were produced in three different mixers: a confi ned impinging jet mixer (CIJM), a two-inlet vortex mixer (VM) and a four-inlet vortex mixer (MIVM). Various process parameters, such as polymer and menthol concentrations, fl ow rates, quench ratio, and solvent type (acetone, acetonitrile, or tethahydrofuran) were considered in terms of achievable size, loading, and encapsulation effi ciency.…”

“…Key directions for the development of an innovative approach to study the penetration of formulations through the skin are provided. [1] 1690 Production of Menthol-Loaded Nanoparticles by Solvent Displacement Ada Ferri, Naveeta Kumari, Roberta Peila and Antonello A. Barresi…”