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Changes in the mechanical properties and adhesion of corneocytes as a function of depth and hydration level - Eric Perez

Laboratoire de Physique Statistique, Paris, France

As cutaneous outer layer, the stratum corneum (SC), provides a barrier against the external environment and trans-epidermal water loss. It is formed by stacked dead keratinized cells, called corneocytes, that are mechanically held together by adhesive structures called corneodesmosomes. This layer is continuously self-renewed by shedding of the outer cell layer (desquamation). The mechanical properties and stability of this tissue as well as the selective shedding of cells ensure skin integrity and can be severely altered in various skin conditions (e.g., dry skin, dandruff or dermatitis).

We have measured the adhesion and mechanical properties of SC corneocytes by micro-manipulation. Accordingly, a combination of a thin glass fiber, as a mechanical cantilever, and a high magnification microscope was used. Various cantilever geometries were used to obtain spring constants from 0.01 to 100 N/m. This large range of force measurement allowed us to study the in plane (lateral) and out of plane (vertical) adhesion force between corneocytes ; as well as to obtain information about their mechanical properties (by monitoring their deformability under stress detachment).

The results of adhesion, bending rigidity and extension modulus of single corneocytes and small corneocyte aggregates will be presented. Cells were detached from intact SC under ambient conditions i.e. in biologically relevant conditions. The corneocyte properties were probed in the outer layers, and also at different depths of the SC. The influence of relative humidity and common moisturizing agents (i.e. glycerol) on cell’s mechanical properties, were studied. The results of this study will be discussed in terms of SC structure and mechanics with possible applications in dermatology and cosmetology.


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