RESUMO
Skin sensitization is an allergic reaction caused by certain chemical substances, and is an important factor to be taken into consideration when evaluating the safety of numerous types of products. Although animal testing has long been used to evaluate skin sensitization, the recent trend to regulate such testing has led to the development and use of alternative methods. Skin sensitization reactions are summarized in the form of an adverse outcome pathway consisting of four key events (KE), including covalent binding to skin proteins (KE1), keratinocyte activation (KE2), and dendritic cell activation (KE3). Equivalent alternative methods have been developed for KE1 to KE3, but no valid alternative has yet been developed for the evaluation of KE4 and T-cell activation. Current alternative methods rely on data from KE1 to KE3 to predict the effect of chemicals on skin sensitization. The addition of KE4 data is expected to improve the accuracy and reproducibility of such predictions. The aim of this study was to establish an assay to evaluate KE4 T-cell activation to supplement data on skin sensitization related to KE4. To evaluate T-cell activation, the Jurkat T-cell line stably expressing luciferase downstream of the pro-inflammatory cytokine interleukin-2 promoter was used. After exposure to known skin sensitizing agents and control substances, luciferase activity measurements revealed that this assay was valid for evaluating skin sensitization. However, two skin sensitizers known to have immunosuppressive effects on T-cells reacted negatively in this assay. The results revealed that this assay simultaneously allows for monitoring of the skin sensitization and immuno-suppressiveness of chemical substances and supplements KE4 T-cell activation data, and may thus contribute to reducing the use of animal experiments.
RESUMO
BACKGROUND: Conductive sheets of cellulose and carbon nanomaterials and its human skin applications are an interesting research aspect as they have potential for applications for skin compatibility. Hence it is needed to explore the effects and shed light on these applications. METHOD: To fabricate wearable, portable, flexible, lightweight, inexpensive, and biocompatible composite materials, carbon nanohorns (CNHs) and hydroxyethylcellulose (HEC) were used as precursors to prepare CNH-HEC (Cnh-cel) composite sheets. Cnh-cel sheets were prepared with different loading concentrations of CNHs (10, 20 50,100 mg) in 200 mg cellulose. To fabricate the bio-compatible sheets, a pristine composite of CNHs and HEC was prepared without any pretreatment of the materials. RESULTS: The obtained sheets possess a conductivity of 1.83 × 10- 10 S/m and bio-compatible with human skin. Analysis for skin-compatibility was performed for Cnh-cel sheets by h-CLAT in vitro skin sensitization tests to evaluate the activation of THP-1 cells. It was found that THP-1 cells were not activated by Cnh-cel; hence Cnh-cel is a safe biomaterial for human skin. It was also found that the composite allowed only a maximum loading of 100 mg to retain the consistent geometry of free-standing sheets of < 100 µm thickness. Since CNHs have a unique arrangement of aggregates (dahlia structure), the composite is homogeneous, as verified by transmission electron microscopy (TEM) and, scanning electron microscopy (SEM), and other functional properties investigated by Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), conductivity measurement, tensile strength measurement, and skin sensitization. CONCLUSION: It can be concluded that cellulose and CNHs sheets are conductive and compatible to human skin applications.
