Supplementary Material for: Reducing the Harmful Effects of Infrared Radiation on the Skin Using Bicosomes Incorporating β-Carotene

Aim: In this work the effect of infrared (IR) radiation, at temperatures between 25 and 30°C, on the formation of free radicals (FRs) in the skin is studied. Additionally, the influence of IR radiation at high temperatures in the degradation of skin collagen is evaluated. In both experiments the protective effect against IR radiation of phospholipid nanostructures (bicosomes) incorporating β-carotene (Bcb) is also evaluated. Methods: The formation of FRs in skin under IR exposure was measured near physiological temperatures (25-30°C) using 5,5-dimethyl-1-pyrroline-N-oxide spin trap and electron paramagnetic resonance (EPR) spectroscopy. The study of the collagen structure was performed by small-angle X-ray scattering using synchrotron radiation. Results: EPR results showed an increase in the hydroxyl radical in the irradiated skin compared to the native skin. The skin collagen was degraded by IR exposure at high temperatures of approximately 65°C. The treatment with Bcb reduced the formation of FRs and kept the structure of collagen. Conclusions: The formation of FRs by IR radiation does not depend on the increase of skin temperature. The decrease of FRs and the preservation of collagen fibers in the skin treated with Bcb indicate the potential of this lipid system to protect skin under IR exposure.

研究目的：本研究探讨了温度介于25~30℃的红外（IR）辐射对皮肤内自由基（FRs）生成的影响。此外，还评估了高温红外辐射对皮肤胶原蛋白降解的作用。两项实验中，均同步考察了负载β-胡萝卜素（Bcb）的磷脂纳米结构（bicosomes）对红外辐射的防护效果。
实验方法：在近生理温度（25~30℃）条件下，采用5,5-二甲基-1-吡咯啉-N-氧化物（5,5-dimethyl-1-pyrroline-N-oxide）自旋捕捉剂结合电子顺磁共振（EPR）波谱法，检测红外辐射暴露下皮肤内自由基的生成量。通过同步辐射光源下的小角X射线散射，分析皮肤胶原蛋白的结构变化。
实验结果：电子顺磁共振结果显示，经红外辐射后的皮肤内羟基自由基含量较未处理皮肤显著升高。在约65℃的高温条件下，红外辐射可导致皮肤胶原蛋白发生降解。而经负载β-胡萝卜素（Bcb）的磷脂纳米结构（bicosomes）处理后，皮肤内自由基的生成量显著降低，且胶原蛋白结构得以维持。
研究结论：红外辐射诱导的自由基生成与皮肤温度升高无关。经负载β-胡萝卜素（Bcb）的磷脂纳米结构（bicosomes）处理后，皮肤内自由基含量降低且胶原纤维结构得以保留，表明该脂质体系具备用于红外辐射暴露下皮肤防护的应用潜力。