Impact of physiologically relevant temperatures on dermal absorption of active substances - an ex-vivo study in human skin

Microfluidic Approach for Enhanced Paeoniflorin Transdermal Delivery: A Comparative Study on Different Chips and Mixing Dynamics

Paeoniflorin is a natural pharmaceutical ingredient with a widely biological activity. However, as a hydrophilic drug, the problem of low transdermal rate limits its clinical application. To overcome this shortage, LUVs were used as biocompatible carriers of paeoniflorin in this study. We prepared paeoniflorin-loaded large unilamellar vesicles (LUVs) with W/O/W structure by microfluidics. We used four kinds of chips to prepare paeoniflorin LUVs and explored the effects of the chip structures on LUVs properties applying both experiments and numerical simulations. The difference of fluid mixing mechanisms was analyzed among four different channels, including straight and curved structures. Then we evaluated the differences in skin permeability among the three groups, paeoniflorin aqueous solution group, drug-loaded liposome group and blank liposome & drug mixture group, using the abdominal skin of male mice. The results showed that the structure of the microfluidic channel was a key factor affecting the flow rate and mixing efficiency. The mixing efficiency further affected the liposome size. The mixing efficiency of curved channel was not better than that of a straight channel due to the low flow rate and long mixing time. By the results of transdermal experiments, LUVs could reduce the transdermal time and increase the total transdermal amount. LUVs effectively improved the transdermal absorption efficiency of paeoniflorin. In conclusion, paeoniflorin LUVs with highly efficient transdermal were successfully prepared by using microfluidics. We explored the underlying fluid dynamics that lead to variations in the preparation with different chip structures. The transdermal effect of the LUVs was verified.

Transdermal Drug Delivery Systems (TDDS): Recent Advances and Failure Modes

Transdermal drug delivery systems (TDDS), commonly refered to as "patches", present a nonintrusive technique to provide medication without the need for invasive procedures. These products adhere to the skin and gradually release a specific dosage of medicine at a defined rate into the bloodstream. Compared with other methods of drug delivery, TDDS offer benefits such as reduced invasiveness, convenience for patients, and avoidance of the metabolic processes that occur when drugs are orally consumed. Throughout time, TDDS have been used to provide medications for various medical conditions (such as nicotine, fentanyl, nitroglycerin, and clonidine), and their potential for delivering biologics is currently being explored. This review investigates the current literature on the drug delivery efficacy of medical TDDS through the transdermal route. Additionally, the review addresses potential risks and failure modes associated with TDDS design and development as well as strategies for mitigating such risks. A thorough understanding of failure modes provides a blueprint to mitigate failure and produce high-quality efficacious therapeutics.

An update of skin permeability data based on a systematic review of recent research

The cutaneous absorption parameters of xenobiotics are crucial for the development of drugs and cosmetics, as well as for assessing environmental and occupational chemical risks. Despite the great variability in the design of experimental conditions due to uncertain international guidelines, datasets like HuskinDB have been created to report skin absorption endpoints. This review updates available skin permeability data by rigorously compiling research published between 2012 and 2021. Inclusion and exclusion criteria have been selected to build the most harmonized and reusable dataset possible. The Generative Topographic Mapping method was applied to the present dataset and compared to HuskinDB to monitor the progress in skin permeability research and locate chemotypes of particular concern. The open-source dataset (SkinPiX) includes steady-state flux, maximum flux, lag time and permeability coefficient results for the substances tested, as well as relevant information on experimental parameters that can impact the data. It can be used to extract subsets of data for comparisons and to build predictive models.

Hybrid chitosan-lipid nanoparticles of green tea extract as natural anti-cellulite agent with superior in vivo potency: full synthesis and analysis

The aim of this work is to exploit the advantages of chitosan (CS) as a nanocarrier for delivery of anti-cellulite drug, green tea extract (GTE), into subcutaneous adipose tissue. Primarily, analysis of herbal extract was conducted via newly developed and validated UPLC method. Ionic gelation method was adopted in the preparation of nanoparticles where the effect lecithin was investigated resulting in the formation of hybrid lipid-chitosan nanoparticles. Optimal formula showed a particle size of 292.6 ± 8.98 nm, polydispersity index of 0.253 ± 0.02, zeta potential of 41.03 ± 0.503 mV and an entrapment efficiency percent of 68.4 ± 1.88%. Successful interaction between CS, sodium tripolyphosphate (TPP) and lecithin was confirmed by Fourier-transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. Morphological examination was done using transmission electron microscope and scanning electron microscope confirmed spherical uniform nature of GTE load CS-TPP nanoparticles. Ex vivo permeation study revealed permeability enhancing activity of the selected optimal formula due to higher GTE deposition in skin in comparison to GTE solution. Moreover in vivo study done on female albino Wistar rats carried out for 21 days proved successful potential anti-cellulite activity upon its application on rats’ skin. Histological examination showed significant reduction of adipocyte perimeter and area and fat layer thickness. Results of the current study demonstrated that the developed GTE-loaded CS-TPP nanoparticle comprised of chitosan and lecithin showed permeability enhancing activity along with the proven lipolytic effect of green tea represent a promising delivery system for anti-cellulite activity.

Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure

The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca²⁺) gluconate (as 2.5% Ca²⁺gel and individually (2.84%) or commercially (10%) formulated Ca²⁺solution), magnesium (Mg²⁺) gluconate (2.84%) solution and aluminium (Al³⁺) solution (Hexafluorine®, pure and diluted) on the absorption of fluoride following HF exposure (1-3 min, 100 μl, 30%/0.64 cm²) through human skin was investigated in an ex-vivo diffusion cell model. Fluoride absorption was assessed over 6-24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride-binding decontamination agents (Ca²⁺, Mg²⁺, Al³⁺) or water alone without being significantly different. Ca²⁺ appeared slightly more effective than Mg²⁺ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride-binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.

Reflections on the OECD guidelines for in vitro skin absorption studies

At the 8th conference of Occupational and Environmental Exposure of the Skin to Chemicals (OEESC) (16-18 September 2019) in Dublin, Ireland, several researchers performing skin permeation assays convened to discuss in vitro skin permeability experiments. We, along with other colleagues, all of us hands-on skin permeation researchers, present here the results from our discussions on the available OECD guidelines. The discussions were especially focused on three OECD skin absorption documents, including a recent revision of one: i) OECD Guidance Document 28 (GD28) for the conduct of skin absorption studies (OECD, 2004), ii) Test Guideline 428 (TGD428) for measuring skin absorption of chemical in vitro (OECD, 2004), and iii) OECD Guidance Notes 156 (GN156) on dermal absorption issued in 2011 (OECD, 2011). GN156 (OECD, 2019) is currently under review but not finalized. A mutual concern was that these guidance documents do not comprehensively address methodological issues or the performance of the test, which might be partially due to the years needed to finalize and update OECD documents with new skin research evidence. Here, we summarize the numerous factors that can influence skin permeation and its measurement, and where guidance on several of these are omitted and often not discussed in published articles. We propose several improvements of these guidelines, which would contribute in harmonizing future in vitro skin permeation experiments.