We report a new fluorescence resonance energy transfer (FRET) sensing platform for the sensitive detection of caspase-3 activity in vitro and in cells using NaGdF₄:Yb³⁺,Er³⁺@NaGdF₄ upconversion nanoparticles (UCNPs) as the energy donor and Rhodamine B (RB) as the energy acceptor. The phosphorylated RB-modified peptide containing a caspase-3 cleavage site and cell-penetrating peptide (CPP) motif (sequence, (RB)-DEVDGGS(p)GCGT(p)GRKKRRQRRRPQ) is immobilized on the UCNP surface via the strong coordination interaction between Gd³⁺ ions with phosphate. After the cleavage of DEVD by caspase-3, the RB is released from the UCNP surface and the reduced upconversion luminescence (UCL) is recovered. Under the optimum conditions, the recovery ratio of the UCL is linearly dependent on the caspase-3 concentration within the range of 0.01 to 1000 pg mL⁻¹ and with a limit of detection (LOD) of 0.01 pg mL⁻¹ (S/N = 3). In particular, the as-proposed UCNP-based FRET sensing platform has reasonable selectivity which is successfully employed to monitor caspase-3 activity in drug-induced apoptosis of HeLa cells.

中文翻译：

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基于上转换纳米粒子的荧光共振能量转移系统，可有效检测caspase-3活性†

我们报告了一个新的荧光共振能量转移（FRET）传感平台，用于在体外和细胞中使用NaGdF ₄：Yb ³⁺，Er ³⁺ @NaGdF ₄上转换纳米粒子（UCNPs）作为能量供体来灵敏检测caspase-3活性罗丹明B（RB）作为能量受体。包含caspase-3裂解位点和细胞穿透肽（CPP）基序的磷酸化RB修饰肽（序列（RB）-DEVDGGS（p）GCGT（p）GRKKRRQRRRPQ）通过强配位相互作用固定在UCNP表面在Gd ³⁺之间离子与磷酸盐。在caspase-3切割DEVD之后，RB从UCNP表面释放出来，并且还原的上转换发光（UCL）得以恢复。在最佳条件下，UCL的回收率与caspase-3浓度线性相关，范围为0.01到1000 pg mL ^-1，检出限（LOD）为0.01 pg mL ^-1（S / N = 3）。特别地，如所提议的基于UCNP的FRET感测平台具有合理的选择性，其被成功地用于监测药物诱导的HeLa细胞凋亡中的caspase-3活性。