Fluorescence nanoparticles (FNs) are a type of nano-dots generated during baking process, and their safety on organism is unclear and little is known to their cytotoxicity. In this study, the FNs from instant coffee were purified and characterized. The FNs with an average size about 2.08 nm emitted bright blue fluorescence with lifetime about 2.74 ns. The element and functional groups were analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, respectively. The results indicated that these FNs were internalized in lysosomes and induced apoptosis of normal rat kidney (NRK) and Caco-2 cells. While, the pan-caspase inhibitor, Z-VAD-FMK didn't decrease the rate of apoptosis and cell death of the FNs-treated NRK and Caco-2 cells. These internalized FNs enlarged lysosomes, decreased lysosomal enzyme degradation activity and increased lysosomal pH value. Partial co-localization of receptor-interacting serine-threonine kinase 3 (RIPK3) to lysosomes in FNs-treated cells was observed, and the amount of RIPK1 and RIPK3 increased after treatment with FNs. The results demonstrated that the FNs from instant coffee induced lysosomal membrane permeabilization and initiated necroptosis.

荧光纳米粒子（FNs）是一种在烘烤过程中产生的纳米点，其对生物体的安全性尚不清楚，对其细胞毒性也知之甚少。在这项研究中，对速溶咖啡中的 FN 进行了纯化和表征。平均尺寸约为 2.08 nm 的 FN 发出明亮的蓝色荧光，寿命约为 2.74 ns。元素和官能团分别通过X射线光电子能谱和傅里叶变换红外光谱分析。结果表明，这些 FNs 在溶酶体中内化并诱导正常大鼠肾 (NRK) 和 Caco-2 细胞的凋亡。而泛半胱天冬酶抑制剂Z-VAD-FMK 没有降低 FNs 处理的 NRK 和 Caco-2 细胞的凋亡率和细胞死亡率。这些内化的 FN 扩大了溶酶体，降低了溶酶体酶的降解活性并增加了溶酶体的 pH 值。在 FNs 处理的细胞中观察到受体相互作用的丝氨酸-苏氨酸激酶 3 (RIPK3) 与溶酶体的部分共定位，并且在 FNs 处理后 RIPK1 和 RIPK3 的量增加。结果表明，速溶咖啡中的 FNs 诱导溶酶体膜透化并引发坏死性凋亡。