Effects of solvent and micellar encapsulation on the photostability of avobenzone
Effects of solvent and micellar encapsulation on the photostability of avobenzone
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DOI：
10.1039/c9pp00483a
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发表时间：
2020-03-01
影响因子：
3.1
通讯作者：
Bardeen, Christopher J.
中科院分区：
文献类型：
--
作者：
Hanson, Kerry M.;Cutuli, Miles;Bardeen, Christopher J.
阿伏苯宗（AV）是美国食品和药物管理局批准的唯一一种吸收UVA辐射的紫外线过滤分子，其光降解是防晒制剂中的一个重要问题。本文研究了AV在不同溶剂体系和胶束体系中的物理性质和光稳定性。AV在其酮-烯醇互变异构体中作为有效的UVA防护剂起作用。AV在非极性溶剂和水性聚集体中对光诱导双酮化非常敏感，但在极性质子溶剂（如甲醇）中相当稳定。通过研究其在不同的表面活性剂溶液中的稳定性，我们表明，将AV纳入十二烷基硫酸钠（SDS）胶束可以达到与纯甲醇相当的稳定性水平。稳态光谱位移，荧光各向异性，和时间分辨的荧光衰减测量都与AV经历胶束封装后的极性环境相一致。有人提出，AV被封装在SDS胶束的栅栏层，这允许访问水分子，促进光子吸收和弛豫后的烯醇形式的重新形成。虽然AV互变异构化的详细机制仍不清楚，但这项工作表明，调整AV的化学微环境可能是提高防晒功效的有用策略。
The photodegradation of avobenzone (AV), the only ultraviolet filter molecule approved by the Food and Drug Administration to absorb UVA radiation, is an important problem in sunscreen formulations. In this paper, the photophysics and photostability of AV in various solvent systems and in aqueous micelles are studied. AV in its keto-enol tautomer functions as an effective UVA protection agent. AV is highly susceptible to photoinduced diketonization in both nonpolar solvents and in aqueous aggregates but is considerably more stable in polar, protic solvents like methanol. By studying its stability in different surfactant solutions, we show that incorporation of AV into sodium dodecylsulfate (SDS) micelles can achieve stability levels comparable to neat methanol. Steady-state spectral shifts, fluorescence anisotropy, and time-resolved fluorescence decay measurements are all consistent with AV experiencing a polar environment after micellar encapsulation. It is proposed that AV is encapsulated in the palisade layer of the SDS micelles, which allows access to water molecules that facilitate the re-formation of the enol form after photon absorption and relaxation. Although the detailed mechanism of AV tautomerization remains unclear, this work suggests that tuning the chemical microenvironment of AV may be a useful strategy for improving sunscreen efficacy.