引言#

组胺是重要神经递质，也是肥大细胞颗粒里的关键信号分子。病理状态下颗粒内容物漏进胞质，往往是细胞功能受损甚至坏死的标志。但现有小分子探针多靠单波长读数和共价反应，前者易受探针分布不均和激发光波动干扰，后者动力学慢，很难抓住组胺的快速瞬变。作者要解决的，就是做一个能快速、比率读出、适用于活细胞的组胺探针。

Design of the supramolecular probe for the visualization and quantification of histamine (HA) in mast cells. (A) Schematic illustration of the assembly and sensing mechanism of the probe CB[7]2⊃GA-1, enabling specific and rapid imaging of HA. (B) Chemical structures of the host and guest molecules, along with the reference supramolecular complexes CB[7]⊃GA-2 and CB[7]⊃GA-3.

主要结果#

作者设计阳离子荧光客体GA-1，让它与葫芦[7]脲CB[7]自组装，并通过改变正电荷位置控制组装方式。GA-1的正电荷在分子中心，两个芳香臂被两个CB[7]同时包合，形成CB[7]₂⊃GA-1，发射峰从500 nm红移到560 nm，量子产率51.87%。组胺与CB[7]的结合更强，会把GA-1竞争置换出来，荧光回到500 nm，于是F500/F560成为比率信号。体外检测给出检出限13.2 nM，在0—40 µM范围线性R²=0.996，响应时间0.96 s，表观速率常数3.56 s⁻¹；其他神经递质、氨基酸和生物硫醇的相对响应均低于20%。在活肥大细胞中，探针主要定位胞质，与胞质标记的Pearson相关系数0.93；外源组胺使比率从0.12升到1.55。用尼日利亚霉素或莫能霉素诱导内源组胺释放，尼日利亚霉素更快达到饱和（250 s对350 s），幅度也更大。尼日利亚霉素15、20、50 µM分别对应胞质组胺约18、20、26倍升高，细胞体积膨胀直至膜破裂，呈现剂量、组胺水平和形态恶化同向变化。

Multimodal structural analysis of the supramolecular complex CB[7]2⊃GA-1. (A) Job’s plot for the complexation between GA-1 and CB[7] (total concentration = 30 µm), derived from fluorescence data. χ = [GA-1]/([GA-1]+[CB[7]]). (B) Fluorescence emission spectra of GA-1 (30 µm) upon the addition of varying concentrations of CB[7] in aqueous solution, Ex = 440 nm. Inset: Photographs of the GA-1 solution under 365 nm UV illumination before (left) and after (right) the addition of CB[7]. (C) The linear relationship between the fluorescence intensity ratio (F560 nm/F500 nm) and the concentration of CB[7]. (D) ESI-HR-MS analysis of the supramolecular complex CB[7]2⊃GA-1. (E) 1H NMR spectra of GA-1, CB[7]2⊃GA-1, and CB[7] in D2O at 25°C (0.5 mm). (F) Partial 2D ROESY NMR spectrum of CB[7]2⊃GA-1. (G) ITC isotherm and thermodynamic fitting for the binding between GA-1 and CB[7] in water, [GA-1] (cell) = 10 µm, CB[7] (syringe) = 100 µm. (H) Natural transition orbital (NTO) track plots of the guest GA-1 and the CB[7]2⊃GA-1 complex (CB[7] was omitted for clarity in the right-side part).

Real-time ratiometric fluorescence imaging of HA in mast cells under storage dysfunction model. (A) Fluorescence images of mast cells preincubated with the probe CB[7]2⊃GA-1 (30 µm) and subsequently stimulated with monensin and nigericin (15 µm) over a period of 600 s. Ex = 440 nm. (B) Time course of the fluorescence ratio (F500 nm/F560 nm) under the stimulation conditions described in (A). (C, E, G) Fluorescence ratio F500 nm/F560 nm images and (D, F, H) the corresponding changes in cell volume for mast cells preincubated with CB[7]2⊃GA-1 (30 µm) followed by stimulation with nigericin at concentrations of 15 µm (C, D), 20 µm (E, F), and 50 µm (G, H). Ex = 440 nm. Statistical significance of cell volume changes relative to the control group was determined using Student’s t-test. ns, no significant difference; ****p < 0.0001. Data are presented as mean ± S.D. (n = 5). Scale bars: 20 µm (global images) and 5 µm (enlarged images).

结论#

这项研究把“超分子组装比例调控”变成了一个可用的快速比率传感策略，关键不是单纯做出一个探针，而是让组胺检测快到能跟得上颗粒释放。对真实应用来说，它最直接的落点是药物诱导肥大细胞储存功能障碍的早期预警：谁可以用？做细胞毒性、炎症和肥大细胞病理研究的人。怎么用？用比率荧光同时读组胺泄漏和细胞形态变化。会改变什么？把“组胺升高”和“细胞肿胀、破裂”变成可定量关联的早期指标。但原文证据主要来自肥大细胞和离子载体刺激模型，是否适用于体内、临床样本或更广细胞类型，原文没有验证，不能直接推成临床诊断工具。