A Review of Atomic-Force Microscopy in Skin Barrier Function Assessment.

Skin barrier function (SBF) disorders are a class of pathologies that affect a significant portion of the world population. These disorders cause skin lesions with intense itch, impacting patients' physical and psychological well-being as well as their social functioning. It is in the interest of patients that their disorder be monitored closely while under treatment to evaluate the effectiveness of the ongoing therapy and any potential adverse reactions. Symptom-based assessment techniques are widely used by clinicians; however, they carry some limitations. Techniques to assess skin barrier impairment are critical for understanding the nature of the disease and for helping personalize treatment. This review recalls the anatomy of the skin barrier and describes an atomic-force microscopy approach to quantitatively monitor its disorders and their response to treatment. We review a panel of studies that show that this technique is highly relevant for SBF disorder research, and we aim to motivate its adoption into clinical settings.

Skin Barrier- and Immune Response-Related Biomarkers of Solar UVR Exposure Comparing Indoor and Outdoor Workers.

Outdoor workers have increased risk of developing keratinocyte cancer due to accumulated skin damage resulting from chronic and excessive exposure to UVR. This study aims to identify potential noninvasive biomarkers to assess chronic UVR exposure. We analyzed stratum corneum biomarkers collected from 2 skin locations and 2 occupational groups with contrasting solar UVR exposure: the forehead and retroauricular skin among outdoor workers and indoor workers. Using a linear mixed model adjusting for age and skin phototype, we compared biomarkers between both skin sites in indoor and outdoor workers. We measured markers of the immune response and skin barrier, including cytokines, GFs, 15-hydroxyeicosatetraenoic acid, cis- and trans-urocanic acid, and corneocyte topography, indicated by circular nano objects. Differences between the 2 skin sites were found for cis-urocanic acid, total urocanic acid, IL-1α, IL-1RA, IL-1RA/IL-1α, IL-18, 15-hydroxyeicosatetraenoic acid, CCL4, and circular nano objects. The levels of cis-urocanic acid and CCL4 also differed between indoor and outdoor workers. These findings underscore changes in both immune response and skin barrier induced by UVR. They indicate the potential utility of stratum corneum biomarkers in detecting both chronic UVR exposure in occupational setting and aiding in the development of preventive measures.

Open-source controller for low-cost and high-speed atomic force microscopy imaging of skin corneocyte nanotextures.

High-speed atomic force microscopes (HS-AFMs) with high temporal resolution enable dynamic phenomena to be visualized at nanoscale resolution. However, HS-AFMs are more complex and costlier than conventional AFMs, and particulars of an open-source HS-AFM controller have not been published before. These high entry barriers hinder the popularization of HS-AFMs in both academic and industrial applications. In addition, HS-AFMs generally have a small imaging area that limits the fields of implementation. This study presents an open-source controller that enables a low-cost simplified AFM to achieve a maximum tip-sample velocity of 5,093 µm/s (9.3 s/frame, 512 × 512 pixels), which is nearly 100 times higher than that of the original controller. Moreover, the proposed controller doubles the imaging area to 46.3 × 46.3 µm2 compared to that of the original system. The low-cost HS-AFM can successfully assess the severity of atopic dermatitis (AD) by measuring the nanotexture of human skin corneocytes in constant height DC mode. The open-source controller-based HS-AFM system costs less than $4,000, which provides resource-limited research institutes with affordable access to high-throughput nanoscale imaging to further expand the HS-AFM research community.

Information and Thermodynamics: Fast and Precise Approach to Landauer's Bound in an Underdamped Micromechanical Oscillator.

The Landauer principle states that at least k_{B}Tln2 of energy is required to erase a 1-bit memory, with k_{B}T the thermal energy of the system. We study the effects of inertia on this bound using as one-bit memory an underdamped micromechanical oscillator confined in a double-well potential created by a feedback loop. The potential barrier is precisely tunable in the few k_{B}T range. We measure, within the stochastic thermodynamic framework, the work and the heat of the erasure protocol. We demonstrate experimentally and theoretically that, in this underdamped system, the Landauer bound is reached with a 1% uncertainty, with protocols as short as 100 ms.