Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Berlin, Germany.
Institute for Pharmacy, Pharmacology and Toxicology, Freie Universität Berlin, Berlin, Germany.
J Biophotonics. 2018 Apr;11(4):e201700169. doi: 10.1002/jbio.201700169. Epub 2018 Jan 17.
The question whether nanoparticles can cross the skin barrier is highly debated. Even in intact skin rare events of deeper penetration have been reported, but technical limitations and possible artifacts require careful interpretation. In this study, horizontal scanning by 2-photon microscopy (2 PM) of full-thickness human skin samples placed in a lateral position yielded highly informative images for skin penetration studies of fluorescently tagged nanoparticles. Scanning of large fields of view allowed for detailed information on interfollicular and follicular penetration in tissue blocks without damaging the sample. Images in histomorphological correlation showed that 2P-excited fluorescence signals of fluorescently tagged 20 and 200 nm polystyrene nanoparticles preferentially accumulated in the stratum corneum (SC) and in the upper part of vellus hair follicles (HFs). Rare events of deeper penetration in the SC and in the infundibulum of vellus HFs were observed at sites of high focal particle aggregations. Wide-field 2 PM allows for imaging of nanoparticle penetration in large tissue blocks, whereas total internal reflection microscopy (TIRFM) enables selective detection of individual nanoparticles as well as clusters of nanoparticles in the SC and within the epidermal layer directly beneath the SC, thus confirming barrier crossing with high sensitivity.
纳米颗粒是否能穿透皮肤屏障这一问题备受争议。即使是在完整的皮肤中，也有报道称极少量的纳米颗粒会穿透更深层，但技术限制和可能的伪影需要仔细解读。在这项研究中，将水平放置的全厚人体皮肤样本通过双光子显微镜（2PM）进行横向扫描，为荧光标记纳米颗粒的皮肤穿透研究提供了非常有价值的图像。大视场扫描允许在不损坏样本的情况下，对组织块中毛囊间和毛囊穿透进行详细信息的研究。组织形态学相关性图像显示，20nm 和 200nm 荧光标记聚苯乙烯纳米颗粒的 2P 激发荧光信号优先聚集在角质层（SC）和毳毛毛囊（HF）的上部。在高浓度颗粒聚集的部位，SC 和毳毛 HF 的内囊中观察到极少量的更深穿透事件。宽场 2PM 允许对大组织块中的纳米颗粒穿透进行成像，而全内反射显微镜（TIRFM）能够选择性地检测 SC 中的单个纳米颗粒以及纳米颗粒簇，以及 SC 下方的表皮层，从而以高灵敏度证实了屏障穿透。
