METHODS: Adaxial walls of leaf epidermal cells were characterized using high-pressure-frozen freeze-substituted specimens, which retain their native dimensions during observations using transmission and scanning microscopy, accompanied by energy-dispersive X-ray spectroscopy to identify the role of biogenic silica in wall-based iridescence. Biogenic silica was experimentally removed using aqueous Na2CO3 and optical properties were compared using spectral reflectance.
KEY RESULTS AND CONCLUSIONS: Blue iridescence is produced in the adaxial epidermal cell wall, which contains helicoid lamellae. The blue iridescence from cell surfaces is left-circularly polarized. The position of the silica granules is entrained by the helicoid microfibrillar layers, and granules accumulate at a uniform position within the helicoids, contributing to the structure that produces the blue iridescence, as part of the unit cell responsible for 2 ° Bragg scatter. Removal of silica from the walls eliminated the blue colour. Addition of silica nanoparticles on existing cellulosic lamellae is a novel mechanism for adding structural colour in organisms.
OBJECTIVE: To determine the effect of a physiologically compatible pH moisturizer in atopic dermatitis.
METHODS: A randomized half body, double blind, controlled trial involving patients with stable atopic dermatitis was performed. pH-modified moisturizer and standard moisturizer were applied to half body for 6 weeks.
RESULTS: A total of 6 (16.7%) males and 30 (83.3%) females participated. Skin pH reductions from week 0, week 2 and 6 were significant at the forearms (5.315 [0.98] to 4.85 [0.54] to 5.04 [0.78], p=0.02) and abdomen (5.25 [1.01], 4.82 [0.64], 5.01 [0.59], p=0.00) but not at the shins (5.01 [0.80], 4.76 [0.49], 4.85 [0.79], p=0.09) with pH-modified moisturizer. Transepidermal water loss (TEWL) at the forearms decreased (4.60 [2.55] to 3.70 [3.10] to 3.00 [3.55], p=0.00), abdomen (3.90 [2.90] to 2.40 [3.45] to 2.70 [2.25], p=0.046). SCORAD improved from 14.1±12.75 to 10.5±13.25 to 7±12.25, p=0.00. In standard moisturizer group, pH reductions were significant at the forearms (5.29 [0.94] to 4.84 [0.55] to 5.02 [0.70], p=0.00) and abdomen (5.25 [1.09], 4.91 [0.63], 5.12 [0.66], p=0.00). TEWL at the forearm were (4.80 [2.95], 4.10 [2.15], 4.60 [3.40], p=0.67), shins (3.80 [1.40], 3.50 [2.35], 4.00 [2.50], p=0.91) and abdomen (3.70 [2.45], 4.10 [3.60], 3.40 [2.95], p=0.80). SCORAD improved from 14.2±9.1 to 10.9±10.65 to 10.5±11, p=0.00. Reduction in pH was observed with both moisturizers while TEWL significantly improved with pH-modified moisturizer. pH-modified moisturizer resulted in greater pH, TEWL and SCORAD improvements however the differences were not significant from standard moisturizer.
STUDY LIMITATION: Skin hydration was not evaluated.
CONCLUSION: Moisturization is beneficial for atopic dermatitis; use of physiologically compatible pH moisturizer is promising.