Inspired by the intrinsic catalytic properties of alkaline phosphatase (ALP) and tyrosinase (TYR) as well as the fluorogenic reaction between levodopa and resorcinol, a ratiometric fluorescent probe based on the CdTe/CdS/ZnS/SiO₂ QDs for visual monitoring the activity of ALP was developed. Phosphotyrosine was catalyzed into tyrosine by ALP, and then tyrosine was catalyzed into levodopa by TYR. Carboxyazamonardine, the reactive product of levodopa and resorcinol, gave rise to a strong blue fluorescence at 470 nm and quenched the red fluorescence of CdTe/CdS/ZnS/SiO₂ QDs at 620 nm due to their inner filter effect. Thus, the resulting ratiometric fluorescence acted as the signal output for quantitative ALP detection, accompanying with the fluorescence color changing from red to purple and finally blue for semiquantitative ALP detection. A good linear relationship was obtained ranging from 0.08-500 U L^-1 with the detection limit of 0.02 U L^-1. Moreover, the probe was successfully applied to monitoring ALP activity in human serum samples without any pretreatment, and also used to screen ALP inhibitors. These results suggested that the developed method offered a highly sensitive and promising analytical platform for ALP in clinical diagnostics and paved a new way for monitoring enzymes activity visually for point-of-care diagnosis.

受碱性磷酸酶（ALP）和酪氨酸酶（TYR）的内在催化特性以及左旋多巴和间苯二酚之间的荧光反应的启发，基于CdTe / CdS / ZnS / SiO ₂ QD的比例荧光探针可用于视觉监控开发了ALP。磷酸酪氨酸被ALP催化成酪氨酸，然后酪氨酸被TYR催化成左旋多巴。左旋多巴和间苯二酚的反应产物羧氮莫纳丁在470 nm处发出强烈的蓝色荧光，并淬灭了CdTe / CdS / ZnS / SiO ₂的红色荧光。由于其内部滤光效果，在620 nm处的量子点。因此，所得的比例荧光作为定量ALP检测的信号输出，同时荧光颜色从红色变为紫色，最后变为蓝色以进行半定量ALP检测。在0.08-500 UL ^-1范围内获得了良好的线性关系，检出限为0.02 UL ^-1。此外，该探针无需任何预处理即可成功地用于监测人血清样品中的ALP活性，还可用于筛选ALP抑制剂。这些结果表明，所开发的方法为临床诊断中的ALP提供了一个高度敏感和有希望的分析平台，并为在现场诊断中视觉监控酶活性铺平了新途径。