Ratiometric fluorescence sensors with quantum dots (QDs) as signal reporters have been widely used in biomarkers testing. However, there are few reports on the construction of a ratio fluorescence sensor based on the dual action of enzyme reaction and QDs. In this study, a “two-in-one” multifunctional catalytic QDs (BSA-MnO2 QDs) developed by hydrothermal method displayed excellent fluorescent properties and high oxidase-like activity. Its optimal quantum yield and Michaelis–Menten kinetics constants Km were 10.7% and 0.072 mM, respectively. In the presence of an enzyme substrate, the ratiometric signal can be generated indirectly by BSA-MnO2 QDs catalyzing, which was more conducive to the construction of a ratio fluorescence biosensor and made the experiment result more accurate. Based on these advantages, an acid phosphatase (ACP) ratiometric fluorescence biosensor was designed. In the absence of ACP, o-phenylenediamine (OPD) was catalyzed to produce 2,3-diaminophenothiazine (DAP) (the oxidized fluorescent product of OPD) that has an inner-filter effect with BSA-MnO2 QDs. Conversely, in the presence of ACP, l-ascorbic acid-2-phosphate was dephosphorylated to produce ascorbic acid, which inhibited the oxidase-like activity of BSA-MnO2 QDs and prevented the catalytic oxidation of OPD to DAP. The method can achieve the assay of ACP with a detection limit of 0.038 mU/mL. In addition, this effect can be achieved when other natural enzymes catalyze substrates to produce reducing substances. In this study, a universal ratio fluorescence probe (BSA-MnO2 QDs) was discovered and prepared for the first time, which has wide application prospects.
Nan Lv,Shaodong Zhai,Jun Xiong,Nan Hu,Xiang Guo,Zhida Liu,Ruiping Zhang
Pathological thrombus can cause serious acute diseases that present a significant threat to human health, such as myocardial infarction and stroke. Challenges remain in achieving effective thrombolysis and real-time monitoring of therapeutic effects while minimizing side effects. Herein,a multifunctional nanoplatform (TG-OPDEA@UK/MnO 2 -H1080) with enhanced thrombus-permeability was developed to monitor the therapeutic effect of antioxidant-thrombolysis by hydroxyl radical-responsive NIR-II fluorescence imaging. The polyzwitterion poly (oxidized N,N-Diethylaminoethyl methacrylate- co -n-butyl methacrylate) (OPDEA) was prepared as the matrix of nanoparticles to simultaneously loading urokinase (UK) and MnO 2 QDs, as well as NIR-II fluorescent molecule, H-1080. Subsequently, the fibrin targeted peptide CREKA was modified on the surface of the nanoparticles. OPDEA exhibits efficient loading capacity while endowing nanoparticles with the ability to effectively increased penetration depth of UK by 94.1 % into the thrombus, for extensive thrombolysis and fluorescence monitoring. The loaded UK exhibited good thrombolytic effect and greatly reduced the risk of bleeding by 82.6 %. TG-OPDEA@UK/MnO 2 -H1080 showed good thrombolytic efficacy and specific thrombus monitoring in the mouse carotid artery thrombosis model induced by ferric chloride (FeCl 3 ). This work prepares a nanoplatform for thrombolytic therapy and real-time efficacy assessment based on an independent externally forced thrombus penetration delivery strategy.
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