奈米脫層蒙脫石片在防曬乳液上的應用

Abstract

防曬乳液中的成分同時包含物理性防曬劑和化學性防曬劑，化學吸收劑para-aminobenzoic acid(PABA)光反應過程會產生不穩定的中間產物，而二氧化鈦和氧化鋅為好的光觸媒，會加速PABA光降解反應，減少PABA之光穩定性。因此藉由脫層蒙脫石的特殊結構以及對PABA的吸附性，改善防曬乳液對皮膚可能的傷害。 本研究利用UV/vis觀察到二氧化鈦、氧化鋅在紫外光區會使PABA之光吸收度上升，脫層蒙脫石(exMMT)則使PABA的304nm的光吸收度下降，而這四種成分皆會加速PABA的光裂解，並以二氧化鈦有較好的催化能力。以PL分析脫層蒙脫石(exMMT)、不同表面性質之二氧化鈦(TTO、TiO2 Rod)和氧化鋅(ZnO)與PABA相互作用後之發光光譜，結果顯示exMMT、TTO和TiO2 Rod使PABA之347nm發光強度提升，除此之外，PABA被TTO和TiO2 Rod吸附後，使PL光譜有紅位移現象，而ZnO能被PABA放射光347nm激發而產生另一個386nm發光波峰。當提高防曬乳液成分之濃度，PL圖譜中之發光強度有整體降低的趨勢。 將製備之防曬乳液塗抹於豬皮上，以ATR-FTIR分析塗抹防曬乳的豬皮於紫外光照射後的組織變化，其結果顯示豬皮本身在紫外線照射下脂質中CO-O的C=O之特徵峰(ν=1745cm-1)、-CH3之特徵峰(ν=1366cm-1)和C-O之特徵峰(ν=1164cm-1)強度有下降之趨勢，並且伴隨脂質過氧化之特峰徵(ν=1260cm-1)強度的提升。來自蛋白質中胺基酸的amide Ⅱ之特徵峰(ν=1539cm-1)、-COO之特徵峰(ν=1574cm-1)以及來自DNA中PO2-非對稱振動之特徵峰(ν=1231)等特徵峰強度會下降，並伴隨胺基特徵峰(ν=3280cm-1)和PO2-對稱振動特徵峰(ν=1095cm-1)強度則是有上升的趨勢。當豬皮塗抹含有PABA、二氧化鈦和氧化鋅的溶液後，經紫外光照射下，由IR圖譜可以觀察到來自蛋白質和DNA之特徵峰的變化與未處理的豬皮類似，而來自脂質經照光而過氧化的特徵峰(ν=1260cm-1)強度有降低之效果，當溶液成分中含有脫層蒙脫石，更是有效阻礙脂質過氧化反應，並隨紫外光照射時間增長，-CO-O的C=O特徵峰強度上升，胺基特徵峰強度下降。

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.