Polysaccharide-based skin scaffolds with enhanced mechanical compatibility with native human skin.

We report a custom-made technique to synthesize process-convenient skin scaffolds by tuning the mechanical properties of hydrogels based on a few naturally occurring polysaccharides to match the rheological properties of previously established benchmarks, i.e., the ex vivo native human skins. We studied the mechanical parameters using oscillatory shear rheology. At small strain amplitudes, the intrinsic elastic modulus showed an almost linear dependence in the middle and a changing rate profile at the two ends with concentration of the principal hydrogel component variant, i.e., kappa (κ)-carrageenan. At large strain amplitudes, the hydrogels demonstrated intercycle strain-softening behavior, the onset of which was directly proportional to the κ-carrageenan concentration. We observed a concentration match for the intrinsic elastic modulus of the benchmark within this sigmoidal curve fit. Contextually, we need to explore other potent polymeric hydrogel systems to achieve mechanical affinity in terms of multiple rheological parameters derived from both strain amplitude and angular frequency sweeps. Additionally, we carried out diffusion experiments to study caffeine permeation attributes. The hydrogels show improved barrier features with increasing κ-carrageenan concentration. In terms of the penetration flux and total cumulative amount of permeated caffeine, this enhanced mechanical adherence demonstrates comparable penetration features with the commercial 3D skin model.

Hydrogel or ointment? Comparison of five different galenics regarding tissue breathability and transepidermal water loss.

PURPOSE: Five different galenics were analyzed and compared concerning tissue breathability and gas exchange with the environment after an application period of 6 h on pig ear skin. Aim was to find the most suitable galenics for efficient moist treatment for everyday injuries (abrasions, lacerations and cuts) without influencing the transepidermal water loss. METHODS: A quantity of 0.1 g of the different test preparations was applied once topically to an area of 2 cm2. The analysis of the breathability was performed by TEWL (transepidermal water loss) measurements in the first hour after product application. The moisture retention effect was assessed by corneometry in the first 5 h after product application. RESULTS: The hydrogel preparations showed a higher breathability in contrast to a semi-occlusive ointment and petrolatum. The same applies to the moisture penetration of the skin. Here, all hydrogel formulations showed the highest tissue hydration. After 3 h an additional increase in moisture was observed for the areas treated with Tyrosur® CareExpert Wound Gel and the ointment. CONCLUSION: In contrast to petrolatum and the semi-occlusive ointment, treatment with the hydrogels led to a preservation of the breathability and good moistening of the tissue, which is due to the galenics of the gels consisting of water, carbomer and propylene glycol. The increase in moisture after 3 h in areas treated with Tyrosur® CareExpert Wound Gel and the semi-occlusive ointment indicates a sustained moisturizing effect mediated by dexpanthenol.

Corneocyte Nanotexture as Biomarker for Individual Susceptibility to Skin Irritants.

Irritant contact dermatitis is a wide spread occupational skin condition. In addition to generalized protection and teaching schemes, a knowledge about individual risk might add to an improved awareness for hazards. Here, we report on a novel candidate biomarker, which might stage individual susceptibility to irritant skin damage. Subclinical sensitivity was proven in recent studies. As a nano-anatomical measure, it works non-invasively on corneocytes from tape strips. Here, we report on a 7-day course after exposure to sodium lauryl sulphate and compare the novel cell texture index with the classical markers water loss (transepidermal water loss) and natural moisturizing factor. All parameters show a high degree of correlation.

Actinic keratosis and surrounding skin exhibit changes in corneocyte surface topography and decreased levels of filaggrin degradation products.

Actinic keratosis (AK) is a frequent premalignant skin lesion mainly caused by chronic sun exposure. AK lesions are often surrounded by invisible, subclinical alterations, called field of cancerization (FoC). Definition of FoC is of importance for therapy management; however, the criteria and non-invasive tools to characterize FoC are lacking. Atomic force microscopy (AFM) proved to be a suitable tool for detection of changes in the corneocyte surface topography in inflammatory skin diseases, which share similar clinical features with AK such as hyper- and parakeratosis. Therefore, in this study we applied AFM to investigate AK and surrounding skin obtained by non-invasive collection of the stratum corneum (SC) with adhesive tapes. Furthermore, we determined degradation products of structural protein filaggrin (natural moisturizing factor, NMF), which previously showed association with the changes in corneocyte surface topography. Ten patients with multiple AK on the face were recruited from the outpatient clinic. SC samples were collected from the AK lesion, skin sites adjacent to the AK, 5 cm from the AK and retroauricular area. Corneocyte surface topography was determined by AFM, and NMF by liquid chromatography. The AK lesion showed alterations of the corneocyte surface topography characterized by an increased number of nanosize protrusions, which gradually decreased with the distance from the lesion. NMF levels show an inverse pattern. Atomic force microscopy showed to be a suitable tool to detect changes in the corneocyte surface topography on the AK lesion and surrounding skin in a non-invasive manner.

Linear viscoelastic and microstructural properties of native male human skin and in vitro 3D reconstructed skin models.

The study reports first ever account of measurements of linear viscoelastic moduli under small amplitude oscillatory shear deformations, for commercially available juvenile and aged in vitro 3D reconstructed skin models. The results were compared with those of native male whole human and dermis-only foreskin samples, catering to a wide age group from 0.5 to 68 years, including samples from a 23-year-old male abdomen. In the strain sweep tests, the dermis of the juvenile/young age group assumed a higher intrinsic elastic modulus than the whole skin. A reverse qualitative trend was noted for the adult/aged age group. Confirmed by the histological examination of the stained cross-sections, this is attributed to the nascent epidermal differentiation and the high fiber density of dermal collagen. The oscillation frequency sweeps exposed a greater dependence of the elasticity on the frequency for the native male dermis foreskin samples as compared to the whole skins, irrespective of age. This is anticipated since the extremely structured epidermis confers higher resistance to the whole skins towards intracycle deformations compared to the dermis, thereby storing smaller elastic energy. The 3D skin models examined in this work exhibited a broader linear viscoelastic region, a larger viscoelasticity, and much higher dynamic moduli, compared to the native skin. The rheological trends are a significant addition to the literature and may be used as a reference for the design of next generation of scaffolds.