Discover the 'water barrier' of human skin

Scientists have finally found a solution to the waterproof properties of human skin.

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One characteristic of anyone's body is visible, but we understand too little about it: The way our skin forms a water-tight barrier to protect our body from the outside environment. Now that for the first time the basic molecular structure of the skin forms, that barrier has been identified. This finding could pave the way for new technology, allowing drugs to be delivered directly through the skin to minimize harmful side effects.

The structure and function of the skin barrier has long been arousing curiosity of researchers. This barrier is said to be in the outermost layer, the horny layer, and more specifically in a fat that occupies the space between the cells inside this layer.

We had to wait a long time to discover the secret of the 'water barrier' on the skin

To clarify this fat, expert Lars Norlén of Stockholm Karolinska Institute (Sweden) and colleagues shaved the skin from the forehead of 5 volunteers. They put this tissue into a high-pressure freezer that immediately cooled to -140 ^° C. Using this technique, each atom was stored in its natural position.

The researchers then cut the tissue into layers of only 25-50 nanometers thick with a cooled diamond blade and explore these layers with an electron microscope. The stages of the cooling process, tissue positioning and cutting are very complex and require a lot of practice to achieve accuracy.'It takes months to get a single slice but it gives you an unprecedented answer , ' Norlén said.

Indeed, what researchers have witnessed has surprised them. Fat molecules (lipids) have 1 water-absorbing head and 2 water-resistant tails. Usually the two tails are in the same direction, giving the molecule a hairpin shape. A group of lipid molecules often arrange themselves into a two-layer sheet (bilayer) with all tails pointing in the same direction. However, the lipid molecules in the middle of the stratum corneum cells spread out, so the two ends of each molecule point in the opposite direction. These lipid molecules are stacked interchangeably.'By stretching like that, they form a denser structure and are much better waterproof than regular bilayer layers , ' Norlén said.

This special structural fat layer prevents water from passing in any direction except where the skin is changed to form pores.'There is no water present in this extracellular space. It cannot disturb the barrier, thus completely prevailing over the hydration process, which is necessary for a volatile environment in which we live, ' added the Swedish expert.

According to New Scientist, Norlén and his colleagues plan to build a skin-based computer model to help them test drugs that are capable of opening seemingly impenetrable barriers. They hope this will allow widespread use of the drug through the skin and directly into the bloodstream, avoiding harmful side effects when oral medications are metabolized in the liver and intestines. Subcutaneous delivery will also allow doctors to target specific areas and in a better controlled period. Further applications may be to develop a more realistic artificial skin type.