Transepidermal water loss for probing full-thickness skin barrier function: correlation with tritiated water flux, sensitivity to punctures and diverse surfactant exposures

Skin barrier function is a key parameter to consider when performing in vitro percutaneous absorption studies. Whilst tritiated water flux measurements were often used to assess skin integrity, recent decades have witnessed the emergence of the more rapid and user-friendly transepidermal water loss (TEWL) approach. Yet to date, the nature of the correlation between TEWL and skin barrier function in vitro has still not been comprehensively established. In this study, a novel TEWL device, operating on a cold-induced vapour sink principle, was used to probe the barrier function of full-thickness porcine skin. The method was sufficiently sensitive to show the influence of punctures on barrier function although the observed non-linear pattern suggested tissue swelling processes and/or capillary action could be occurring. The results of various surfactant application experiments strongly suggested that TEWL was indeed largely predictive of skin sample integrity. A key finding was that basal TEWL was linearly correlated with basal tritiated water flux (r2 = 0.80, n = 63). Thus, a dedicated TEWL method can be used as a good alternative to water flux measurements for assessing full-thickness skin barrier function

Vibrational-mechanical properties of the highly-mismatched Cd1−xBexTe semiconductor alloy: experiment and ab initio calculations

Abstract The emerging CdTe–BeTe semiconductor alloy that exhibits a dramatic mismatch in bond covalency and bond stiffness clarifying its vibrational-mechanical properties is used as a benchmark to test the limits of the percolation model (PM) worked out to explain the complex Raman spectra of the related but less contrasted Zn1−xBex-chalcogenides. The test is done by way of experiment ( $$x\le 0.11$$ x ≤ 0.11 ), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations ( $$x$$ x  ~ 0–0.5; $$x$$ x ~1). The (macroscopic) bulk modulus $${B}_{0}$$ B 0 drops below the CdTe value on minor Be incorporation, at variance with a linear $${B}_{0}$$ B 0 versus $$x$$ x increase predicted ab initio, thus hinting at large anharmonic effects in the real crystal. Yet, no anomaly occurs at the (microscopic) bond scale as the regular bimodal PM-type Raman signal predicted ab initio for Be–Te in minority ( $$x$$ x ~0, 0.5) is barely detected experimentally. At large Be content ( $$x$$ x ~1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular ( $$x$$ x ~0, 0.5) and inverted ( $$x$$ x ~1) Be–Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to Cd1−xBexTe without further refinement, albeit in a “relaxed” form. This enhances the model’s validity as a generic descriptor of phonons in alloys