Using skin patches to deliver drugs is dependable and doesn\'t have the same issues as permeation enhancers, which help drugs get through the skin but struggle because of the skin\'s natural barrier. Strategies are required to increase topical bioavailability to enhance drug absorption. Natural compounds offer a promising solution by temporarily reducing skin barrier resistance and improving drug absorption. Natural substances allow a wider variety of medications to be distributed through the stratum corneum, offering a dependable approach to enhancing transdermal drug delivery. Natural substances have distinct advantages as permeability enhancers. They are pharmacologically effective and safe, inactive, non-allergenic, and non-irritating. These characteristics ensure their suitability for use without causing adverse effects. Natural compounds are readily available and well tolerated by the body. Studies investigating the structure-activity relationship of natural chemicals have demonstrated significant enhancer effects. By understanding the connection between chemical composition and enhancer activity, researchers can identify effective natural compounds for improving drug penetration. In conclusion, current research focuses on utilizing natural compounds as permeability enhancers in transdermal therapy systems. These substances offer safety, non-toxicity, pharmacological inactivity, and non-irritation. Through structure-activity relationship investigations, promising advancements have been made in enhancing drug delivery. Using natural compounds holds enormous potential for improving the penetration of trans-dermally delivered medications.

Ion pairing is a strategy used to increase the permeation of topically applied ionised drugs. Formation occurs when the electrostatic energy of attraction between oppositely charged ions exceeds their mean thermal energy, making it possible for them to draw together and attain a critical distance. These ions then behave as a neutral species, allowing them to partition more readily into a lipid environment. Partition coefficient studies may be used to determine the potential of ions to pair and partition into an organic phase but cannot be relied upon to predict flux. Early researchers indicated that temperature, size of ions and dielectric constant of the solvent system all contributed to the formation of ion pairs. While size is important, this may be outweighed by improved lipophilicity of the counter ion due to increased length of the carbon chain. Organic counter ions are more effective than inorganic moieties in forming ion pairs. In addition to being used to increase permeation, ion pairs have been used to control and even prevent permeation of the active ingredient. They have also been used to stabilise solid lipid nanoparticle formulations. Ion pairs have been used in conjunction with permeation enhancers, and permeation enhancers have been used as counter ions in ion pairing. This review attempts to show the various ways in which ion pairs have been used in drug delivery via the skin. It also endeavours to extract and consolidate common approaches in order to inform future formulations for topical and transdermal delivery.

BACKGROUND: Cosmetic Skin Delivery has a very important impact on the action of cosmetics. More and more cosmetic manufacturers are focusing on cosmetic delivery. Meanwhile, it also brings safety issues and the customization of national laws and regulations.
OBJECTIVE: This paper reviews the theoretical knowledge about cosmetic skin delivery and evaluation methods.
METHODS: An extensive literature search was conducted using PubMed, Web of Science, and other databases for articles on transdermal/skin delivery in cosmetics from 1985 to 2020.
RESULTS: The importance of skin delivery in cosmetics is outlined. The structure of the skin and the skin barrier, including delivery pathways available to cosmetic molecules in three modalities are introduced. The laws and regulations of various countries on nanomaterials for cosmetics are listed. The in vitro skin absorption test methods for cosmetics are briefly reviewed. Furthermore, the prospect of future skin penetration methods for cosmetics is presented.
CONCLUSIONS: Currently, various methods to enhance and evaluate cosmetic delivery through skin are available. However, there are no unified domestic and international laws and regulations about evaluation of transdermal delivery. This article provides a new perspective on the development of novel permeation enhancement technologies.

Non-metallic pipe (NMP) materials are used as an internal lining and standalone pipes in the oil and gas industry, constituting an emerging corrosion strategy. The NMP materials are inherently susceptible to gradual damage due to creep, fatigue, permeation, processing defects, and installation blunder. In the presence of acid gases (CO2, H2S), and hydrocarbons under high pressure and temperature, the main damage is due to permeation. The monitoring of possible damage due to permeation is not well defined, which leads to uncertainty in asset integrity management. Assessment of permeation damage is currently performed through mechanical, thermal, chemical, and structural properties, employing Tensile Test, Differential Scanning Calorimetry (DSC), Fourier-transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM), to evaluate the change in tensile strength, elongation, weight loss or gain, crystallinity, chemical properties, and molecular structure. Coupons are commonly used to analyze the degradation of polymers. They are point sensors and did not give real-time information. Polymers are dielectric materials, and this dielectric property can be studied using Impedance Analyzer and Dielectric Spectroscopy. This review presents a brief status report on the failure of polymer liners in pipelines due to the exposure of acid gases, hydrocarbons, and other contaminants. Permeation, liner failures, the importance of monitoring, and new exclusive (dielectric) property are briefly discussed. An inclusive perspective is provided, showing the challenges associated with the monitoring of the polymer liner material in the pipeline as it relates to the life-time prediction requirement.

Occupational hand eczema is common among hairdressers, and protective gloves are important in limiting exposure to irritants and allergens. Various glove types may differ in their protective ability, and their use may lead to hand eczema due to skin irritancy and allergy. MEDLINE was searched for studies investigating permeation of gloves to irritants and allergens used in the hairdressing trade, as well as adverse effects of glove use affecting hairdressers. Forty-four studies were identified; nine reported on permeation. Of those, two in vitro studies found nitrile rubber (NR) gloves to give the best protection when handling hair dyes. Polyethylene (PE) gloves had the lowest reported break-through time. The prevalence of sensitization to rubber materials in European hairdressers was as follows: thiuram mix, median 2.5% (range 0%-8.2%), weighted average 3.0% (95% confidence interval [CI] 3.0%-3.1%); mercapto mix, median 0.4% (range 0%-3.3%), weighted average 0.5% (95% CI 0.47%-0.50%), mercaptobenzothiazole, median 0.6% (range 0%-6.6%), weighted average 0.7% (95% CI 0.6%-0.7%), NRL-type I allergy, median 1.3% (range 1%-16.4%), weighted average 4.0% (95% CI 3.6%-4.5%). In conclusion, NR gloves provide the best skin protection for hairdressers, although natural rubber latex (NRL) and polyvinylchloride (PVC) gloves may be sufficient in most cases. PE gloves are not recommended. Synthetic rubber gloves with low or no levels of accelerators are preferred.

Microparticulate drug delivery systems have shown a great interest in the pharmaceutical area. They allow the increase of drug therapeutic efficacy and the reduction of side effects. In this context, microsponges represent a new model of porous polymer microspheres, which allow the entrapment of a wide range of active agents. During the development, it is necessary the characterization of the system and among of the most important tests are the release and permeation profile analysis. They can demonstrate the behavior of drug in a specific site with a particular application condition and are related to therapeutic efficacy. Therefore, this review provides an overview of drug delivery profile from microsponges. Methods for determination of in vitro release and ex vivo permeation studies are detailed. Examples of drug delivery from microsponges administered in different sites are also discussed with aim to provide an understanding of the use of this strategy to modify the drug delivery.

Peptides are therapeutic molecules that can treat selectively and efficiently a wide range of pathologies. However, their intrinsic properties cause their rapid degradation in the human gastrointestinal (GI) tract resulting in poor bioavailability after oral administration. Yet, their encapsulation in nanocarriers offers them protection from this harsh environment and increases their permeability across the epithelium border. In particular, Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC) have proven to improve peptide oral bioavailability. This article details different techniques used to produce SLN and NLC with potential or effective peptide encapsulation. Basic principles of covalent and non-covalent lipidization are described and discussed as a prerequisite to improve hydrophilic peptide encapsulation in lipid-based nanosuspensions. The last part of this review provides the key evaluation techniques to assay SLN and NLC for peptide oral bioavailability enhancement. Methods to assess the protective effects of the carriers are described as well as the techniques to evaluate peptide release upon lipid digestion by lipases. Furthermore, this review suggests different techniques to measure permeability improvements and describes the main in vitro cell models associated.

Hydrogen in materials is an important topic for many research fields in materials science. Hence in the past quite a number of different techniques for determining the amount of hydrogen in materials and for measuring hydrogen permeation through them have been developed. Some of these methods have found widespread application. But for many problems the achievable sensitivity is usually not high enough and ready-to-use techniques providing also good spatial resolution, especially in the submicron range, are very limited, and mostly not suitable for widespread application. In this work this situation will be briefly reviewed and a novel scanning probe technique based method introduced.