Applications of Exfoliated Montmorillonite on Sunscreen Formulations
Date Issued
2011
Date
2011
Author(s)
Wang, Li-Hsun
Abstract
Sunscreen contains both organic and inorganic active ingredients. The organic active ingredient such as para-aminobenzoic acid (PABA) can produce several reactive intermediates under sunlight, and inorganic active ingredients, such as titanium dioxide and zinc oxide, are a well-known semiconductor with photocatalytic properties. When titanium dioxide and zinc oxide are combined with organic filters in sunscreen formulation, they would act as a photocatalyst to accelerate the degradation of organic molecules. To reduce the above-mentioned undesired side effects from UV Sunscreens, we employed the exfoliated montmorillonite(exMMT) as the sunscreen ingredient and investigated its effect on the degradation of organic ingredients and possible protection for the humanskin under UV irradiation.
The experimental results show that the presence of titanium dioxide (TTO and TiO2 Rod) and zinc oxide (ZnO) could increase the UV-vis absorption of PABA at ultraviolet region, but exMMT decreased the UV-vis absorption at 304 nm. All these four ingredients have the catalytic effect on the photochemical reaction of PABA, especially titanium dioxide.
The presence of exMMT and titanium dioxide nanoparticles (TTO and TiO2 Rod) could also increase the PL intensities of PABA at 347nm. Besides, the formation of PABA dimer and aggregation adsorbing on TTO and TiO2 Rod caused a red shift of PL spectrum. Moreover, ZnO could be excited by the emission light from PABA at 347nm and emitted another peak at 386 nm.
To analyze the effect of sunscreen lotion on the changes of pig skin tissue after exposure to UV light, we wiped the sunscreen lotion on pigskin and exposed it to the UV irradiation, which was then subjected to measure the IR spectra by ATR-FTIR. The results showed that for the pristine pigskin, the intensities of characteristic peaks of lipids such as of -C=O at 1745cm-1, -CH3 at 1366cm-1 and C-O at 1164cm-1 decreased with increasing the intensity of 1260cm-1, which has been attributed to the formation of peroxide groups from the peroxidative damage of lipids. The intensities of the characteristic peaks related to the proteins such as amide Ⅱ at 1539cm-1 and -COO non-symmetric stretching vibration at 1574cm-1 decreased with increasing the intensity of 3280cm-1from NH2. As to the characteristic peaks related to DNA, PO2- asymmetric vibration at 1231cm-1 decreased, whereas PO2-symmetric vibration at 1095cm-1 increased. Interestingly, after applying the sunscreen containing the individual PABA, TiO2, ZnO, and their conbinations, the intensity of 1260cm-1 related to the lipid peroxidation weakened, whereas the characteristic peaks of protein and DNA were barely changed compared to the pristine pigskin. When the exMMT was included in the formulation of sunscreen, it significantly hindered the lipid peroxidation along with increasing the intensities of C=O peak and decreasing the intensity of NH2 peak under UV irradiation.
Subjects
montmorillonite
titanium dioxide
pigskin
para-aminobenoic acid
sunscreen
Type
thesis
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