The overall goal of this research project has been to provide an understanding of how and why Human skin ruptures and to elucidate the degradative effects of ageing, the growth of bacteria on skin associated with diseases, and ultraviolet light from the Sun and UV-C disinfection devices. Skin is a highly complex tissue, comprised of multiple layers; the innermost hypodermis, intermediate dermis, and superficial epidermis. The most superficial epidermal layer, or stratum corneum, acts as a barrier from physical, microbial, and chemical harm. This research has firstly revealed how lipids within the skin barrier prevent bacterial invasion into skin tissue. When these lipids are depleted, which can happen with occupational over washing or with skin disorders such as atopic dermatitis (eczema), Staphylococcus aureus bacterial biofilms can penetrate across the skin barrier and disrupt the skin cell layer that causes regeneration of the epidermis; the basal layer. Taken together, bacterial penetration may be the cause, rather than the result of the disease, as is currently thought. Secondly, research has evaluated the long held prevailing paradigm that macroscopic testing techniques report meaningful information about the mechanical properties of compositionally heterogeneous tissues, which many soft tissues are. Skin exhibits a rich topographical network of microchannels at small scales. Our research has demonstrated that these topographical features govern crack propagation pathways, increasing the variability of measured mechanical properties. Thirdly, studies have revealed how ageing notably alters the mechanical properties of skin. With age, the dermal layer reduces in stiffness and toughness while the outermost skin barrier becomes significantly stiffer and more brittle, increasing the likelihood of rupture. Ageing is also known to reduce the collagen content in the dermis. This project research has revealed for the first time how wrinkles form in skin with ageing. In-vivo, skin experiences forces caused by the preferential orientation of the collagen fibers. When skin is stretched, it contracts in the direction perpendicular to these forces. With ageing, this contraction notably increases, resulting in increases in the depth and width of wrinkles that form. Changes in the mechanical properties of skin with age also promote this wrinkling. Finally, we have demonstrated the extent to which ultraviolet light from the Sun and UV-C disinfection devices can cause photodamage to the skin. All three ultraviolet ranges (UVA, UVB and UVC) light can weaken the skin barrier and make it easier to break. However, no one UV range is more damaging that another. Rather it the amount of energy that the skin absorbs that scales with tissue weakening. In contrast, in the deeper dermal layer, UV light causes skin to become stiffer and tougher, making the skin more ‘leathery’. Changes in the mechanical properties of full thickness skin also scale with the energy absorbed. Collectively, we anticipate that these advances and discoveries will have notable impact on the treatment and prevention of bacterial skin diseases, improvement to patient care in hospitals, CDC guidance regarding UV-C germicidal technologies and radiation exposure risk to the general public, especially during pandemics, and advances in consumer cosmetics and flexible electronics.  

Last Modified: 12/01/2023
Modified by: Guy German