Role of sunscreen formulation and photostability to protect the biomechanical barrier function of skin

Abstract

The impact of sunscreen formulations on the barrier properties of human skin are often overlooked leading to formulations with components whose effects on barrier mechanical integrity are poorly understood. The aim of this study is to demonstrate the relevance of carrier selection and sunscreen photostability when designing sunscreen formulations to protect the biomechanical barrier properties of human stratum corneum (SC) from solar ultraviolet (UV) damage. Biomechanical properties of SC samples were assayed after accelerated UVB damage through measurements of the SC's mechanical stress profile and corneocyte cohesion. A narrowband UVB (305–315 nm) lamp was used to expose SC samples to 5, 30, 125, and 265 J cm −2 in order to magnify damage to the mechanical properties of the tissue and characterize the UV degradation dose response such that effects from smaller UV dosages can be extrapolated. Stresses in the SC decreased when treated with sunscreen components, highlighting their effect on the skin prior to UV exposure. Stresses increased with UVB exposure and in specimens treated with different sunscreens stresses varied dramatically at high UVB dosages. Specimens treated with sunscreen components without UVB exposure exhibited altered corneocyte cohesion. Both sunscreens studied prevented alteration of corneocyte cohesion by low UVB dosages, but differences in protection were observed at higher UVB dosages indicating UV degradation of one sunscreen. These results indicate the protection of individual sunscreen components vary over a range of UVB dosages, and components can even cause alteration of the biomechanical barrier properties of human SC before UV exposure. Therefore, detailed characterization of sunscreen formulation components is required to design robust protection from UV damage.

Skin biophysical properties including impaired skin barrier function determine ultraviolet sensitivity

“…The exact mechanisms for these trends need further investigation and a study with a larger population is needed to achieve more statistical significance. However, the results of the present study are meaningful as the study mimicked the real life conditions of the skin 27 This is primarily due to the effects on the stratum corneum cell cohesion and mechanical integrity by alteration of intercellular lipids and corneodesmosomes. 28 A previous study regarding cumulative exposures to suberythemal dose demonstrated that cutaneous damages, such as the induction of sunburn cells, alteration of Langerhans cells, and active melanocytes, occur even without erythema formation.…”

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

“…In that study, a decrease in DTI was associated with decrease in elastic modulus revealing alterations in the mechanical properties of the corneocytes, likely caused by reduced hydration leading to the shrinkage of the cornified envelope. Interestingly, Berkey et al showed that skin exposure to UVR caused decrease in the surface cohesion, this effect being reverted after treatment with an emollient or humectant. In concordance with the study of Berkey et al, showing alterations in mechanical properties of corneocytes after UVR, Engebretsen et al found elevated DTI levels on the cheek in participants who self‐reported higher exposure to sunlight.…”

“…Interestingly, Berkey et al showed that skin exposure to UVR caused decrease in the surface cohesion, this effect being reverted after treatment with an emollient or humectant. In concordance with the study of Berkey et al, showing alterations in mechanical properties of corneocytes after UVR, Engebretsen et al found elevated DTI levels on the cheek in participants who self‐reported higher exposure to sunlight.…”

Quantifying the inovation of cosmetic formulations that contains phenolic rich fruit extracts as fotoprotective bioactives

“…Cosmetic products kwon as sunscreen are frequently used to prevent skin damage promoted by UV radiation 8 . The active ingredients of these products are called UV filters and are substances capable of absorbing, scattering or reflecting solar radiation.…”