Abstract

Phototherapy is a conventional antipsoriatic approach based on oxygen-relevant generation of oxidative stress to inhibit keratinocyte hyperproliferation. However, this therapy can be restricted due to local hypoxia in psoriatic lesions. The generation of alkyl radicals is oxygen-independent and suppresses hyperproliferation. Herein, we established alkyl radical-based therapy to treat psoriatic hyperplasia. Because alkyl radicals are short-lived compounds, we loaded 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) as a precursor of alkyl radicals into the chitosan nanogels to improve stability. The present study presented a topically applied nanogel that led to a pH-responsive network sensitive to skin pH. This pH responsiveness of the nanogels allowed fast alkyl radical release in the target site. The physicochemical properties of the prepared nanogels were determined through size, zeta potential, scanning electron microscopy, and absorption spectroscopy. The antipsoriatic activity was examined with keratinocyte- and animal-based studies. The nanogels displayed a smooth and spherical morphology with a hydrodynamic diameter of 215 nm. This size was largely increased as the environmental pH increased to 6. The nanogels heated at 44 °C produced alkyl radicals to induce keratinocyte death through the necrosis pathway. Bioimaging demonstrated that topically applied nanogels could deliver alkyl radicals into the epidermis. This targeting was accompanied by the accumulation of free radicals in the epidermis according to the 2′,7′-dichlorodihydrofluorescein diacetate assay. The imiquimod-stimulated psoriasiform animal model indicated a remarkable reduction in erythema, scaling, and overexpressed cytokines upon topical treatment of the nanogels. The transepidermal water loss of the psoriasiform skin was inhibited from 51.7 to 27.0 g/m²/h, suggesting barrier function recovery by the nanocarriers. The nanogels lowered hyperplasia by decreasing the epidermal thickness from 212 to 89 μm. The incorporation of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) as a pH-sensitive fluorescence dye in the nanogels could be used to diagnose the severity of the psoriasiform plaque due to the stronger fluorescence of HPTS in skin with lower pH (psoriasiform skin pH = 4.4) than in healthy skin (pH = 4.9). It was possible to deliver the prepared nanogels into the epidermis to restrain hyperplasia without causing cutaneous irritation.

摘要

光疗是一种传统的抗银屑病方法，其基于与氧相关的氧化应激的产生来抑制角质形成细胞过度增殖。然而，由于银屑病皮损局部缺氧，这种疗法可能受到限制。烷基自由基的产生不依赖于氧并抑制过度增殖。在此，我们建立了基于烷基自由基的疗法来治疗银屑病增生。由于烷基自由基是短寿命的化合物，我们将2,2'-偶氮双[2-(2-咪唑啉-2-基)丙烷]二盐酸盐(AIPH)作为烷基自由基的前体负载到壳聚糖纳米凝胶中以提高稳定性。本研究提出了一种局部应用的纳米凝胶，可形成对皮肤 pH 值敏感的 pH 响应网络。纳米凝胶的 pH 响应性允许烷基自由基在目标位点快速释放。通过尺寸、zeta 电位、扫描电子显微镜和吸收光谱测定所制备的纳米凝胶的物理化学性质。通过角质形成细胞和动物研究检查了抗银屑病活性。纳米凝胶表现出光滑的球形形态，流体动力学直径为215 nm。随着环境 pH 值增加到 6，该尺寸大幅增加。在 44 °C 下加热的纳米凝胶产生烷基自由基，通过坏死途径诱导角质形成细胞死亡。生物成像表明，局部应用的纳米凝胶可以将烷基自由基输送到表皮中。根据 2',7'-二氯二氢荧光素二乙酸酯测定，这种靶向伴随着表皮中自由基的积累。咪喹莫特刺激的银屑病动物模型表明，纳米凝胶局部治疗后红斑、鳞屑和细胞因子过度表达显着减少。银屑病皮肤的经皮水分流失被抑制在51.7g/m ² /h至27.0g/m 2 /h，表明纳米载体恢复了屏障功能。纳米凝胶通过将表皮厚度从 212 微米减少到 89 微米来降低增生。在纳米凝胶中掺入 8-羟基芘-1,3,6-三磺酸 (HPTS) 作为 pH 敏感荧光染料，可用于诊断银屑病斑块的严重程度，因为 HPTS 在皮肤中的荧光强度较低，可用于诊断银屑病斑块的严重程度。 pH 值（银屑病皮肤 pH = 4.4）高于健康皮肤（pH = 4.9）。可以将制备的纳米凝胶递送到表皮中以抑制增生而不引起皮肤刺激。