Sun Zheng Juan, Jiang Jun Ze, Li Yuan Fang
Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University), Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China.
Analyst. 2015 Dec 21;140(24):8201-8. doi: 10.1039/c5an01673h.
Herein, we present a novel strategy based on a "turn-on" fluorescence system made up of metal-organic frameworks Fe-MIL-88 and H2O2 for detecting biothiols in human serum. The nonfluorescent Fe-MIL-88 gives weak fluorescence in the presence of H2O2. Interestingly, it was found that biothiols such as glutathione (GSH), cysteine (Cys) or homocysteine (Hcy) could induce fluorescence turn-on of the Fe-MIL-88/H2O2 system. Under optimal conditions, the relative fluorescence intensity exhibited a good linear relationship in the range from 50 nM-10 μM for GSH (r = 0.994), 50 nM-10 μM for Cys (r = 0.990), and 50 nM-10 μM (r = 0.992) for Hcy; the detection limits of GSH, Cys and Hcy were 30 nM, 40 nM, and 40 nM respectively. Mechanism investigation reveals that biothiols could associate with Fe-MIL-88 via hydrogen bonding and electrostatic interaction followed by redox reaction between biothiols and Fe(3+) present in the Fe-MIL-88, Fe(3+) was thus reduced to Fe(2+), and then Fe(2+) could efficiently catalyze the decomposition of H2O2 to yield ˙OH radicals through the Fenton reaction. Besides, biothiols were able to reduce H2O2 to produce ˙OH radicals directly. Thus the Fe-MIL-88 as well as biothiols could cooperatively contribute to the activation of H2O2 to generate higher amounts of ˙OH radicals, which in turn oxidize the free ligand terephthalic acid (BDC) outside or within the Fe-MIL-88 structure to strongly fluorescent hydroxylated terephthalic acid (OHBDC), thereby turning on the fluorescence.
在此，我们提出了一种基于由金属有机框架Fe-MIL-88和H2O2组成的“开启”荧光系统来检测人血清中生物硫醇的新策略。无荧光的Fe-MIL-88在H2O2存在下发出微弱荧光。有趣的是，发现谷胱甘肽（GSH）、半胱氨酸（Cys）或同型半胱氨酸（Hcy）等生物硫醇可诱导Fe-MIL-88/H2O2系统的荧光开启。在最佳条件下，相对荧光强度在50 nM至10 μM范围内对GSH（r = 0.994）、50 nM至10 μM对Cys（r = 0.990）以及50 nM至10 μM对Hcy（r = 0.992）呈现良好的线性关系；GSH、Cys和Hcy的检测限分别为30 nM、40 nM和40 nM。机理研究表明，生物硫醇可通过氢键和静电相互作用与Fe-MIL-88结合，随后生物硫醇与Fe-MIL-88中存在的Fe(3+)之间发生氧化还原反应，Fe(3+)因此被还原为Fe(2+)，然后Fe(2+)可通过芬顿反应有效催化H2O2分解产生˙OH自由基。此外，生物硫醇能够直接将H2O2还原以产生˙OH自由基。因此，Fe-MIL-88以及生物硫醇可协同促进H2O2的活化以产生更多量的˙OH自由基，这些自由基进而将Fe-MIL-88结构外部或内部的游离配体对苯二甲酸（BDC）氧化为强荧光的羟基化对苯二甲酸（OHBDC），从而开启荧光。
