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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. [ABSTRACT FROM AUTHOR]

A novel magnetic nanozyme Fe3O4@MXene-Au nanocomposite, which possessed higher peroxidase-like activity than that of Fe3O4 nanoparticles and Fe3O4@MXene nanocomposites, was developed. The outstanding magnetic properties of the nanozyme endowed it with the ability of simple and rapid separation, achieving great recyclability. Based on Fe3O4@MXene-Au nanocomposites and glucose oxidase (Glu Ox), a highly selective colorimetric biosensor for glucose detection was developed. Fe3O4@MXene-Au nanocomposites can catalyze H2O2 produced from glucose catalyzed by glucose oxidase to ·OH and oxidize colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) with a significant absorbance at 652 nm. The linear range of glucose was 0–1.4 mM under optimal conditions, with a limit of detection (LOD) of 0.11 mM. Glucose in human whole blood was successfully detected with satisfactory recoveries. Furthermore, a facile agarose hydrogel detection platform was designed. With smartphone software, glucose detection can be realized by the agarose hydrogel platform, demonstrating the potential in on-site and visual detection of glucose. [ABSTRACT FROM AUTHOR]

A selective method for the determination of myosmine (a tobacco alkaloid) was developed using molecularly imprinted polymers (MIPs) based on Fe3O4@SiO2 and PAMAM dendrimers. Fe3O4@SiO2 with excellent magnetism and rapid separation performance was chosen as carrier for the MIPs. Moreover, the MIPs modified with PAMAM dendrimers exhibited a regular structure and abundant functional groups, which improve the efficiency of imprinting sites. The myosmine concentration was measured by HPLC with PDA detector, and the UV detection wavelength was set to 200 nm. The linear range of this assay was 13.2–400 mg/L with a correlation coefficient of 0.999, and the detection limit was 4.0 mg/L (S/N = 3). The MIPs have been used for the determination of myosmine in cigarettes, and the recovery range was 84.2–93.5%, with RSD values in the range 0.41–3.1%. In conclusion, our MIPs combine advantages of simple preparation and remarkable selectivity, which gives them excellent application prospects for the sensitive determination of trace myosmine in tobacco products. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2 ) has been reported to mediate a variety of physiological and pathological processes in living systems. In this work, a biosensor for determination of H 2 O 2 was prepared by using an HRP/Ti 3 C 2 /Nafion film-modified glassy carbon electrode (GCE). Ti 3 C 2 nanosheets with remarkable conductivity and high specific surface area were chosen as carriers for HRP. Moreover, this biosensor modified with HRP has a specific catalytic effect on H 2 O 2 . The difference in peak current could reflect the quantitative change of H 2 O 2 . The linear range of the biosensor is 5-8000 μM, and the detection limit is 1 μM ( S / N = 3). This biosensor was used to detect H 2 O 2 in clinical serum samples of normal controls and patients with acute myocardial infarction (AMI) before and after percutaneous coronary intervention (PCI). The results showed that the difference between normal controls and patients is significant ( P < 0.05), as well as the difference for patients before and after PCI ( P < 0.01), but no significant difference existed between postoperative patients and normal controls. This biosensor has the advantages of simple preparation, high sensitivity, and quick detection, showing potential application in clinical diagnosis.

This study aimed to compare the efficacy and safety of thrombolytic and anticoagulant therapy for acute submassive pulmonary embolism (PE). A retrospective evaluation was performed on 25 consecutive inpatients with acute submassive PE treated by thrombolytic therapy and 25 earlier consecutive inpatients with acute submassive PE treated by anticoagulant therapy. No statistically significant difference in clinical curative effect was identified between the thrombolysis and anticoagulation groups (P>0.05). Following 24 h of therapy, the improvement rates of dyspnea and revascularization in the thrombolysis group achieved statistical significance compared with those of the anticoagulation group (P<0.01 for each). The PO 2 level of the thrombolysis group (81.18±5.66 mmHg) was notably higher than that of the anticoagulation group and the difference was statistically significant (P<0.01). The pulmonary arterial pressures of the thrombolysis group (51.21±6.86 mmHg) were significantly lower than those of the anticoagulation group (60.64±5.17 mmHg) (P<0.01). Furthermore, the difference between the hemorrhage rates of the two groups was statistically significant (P<0.05). Thrombolysis was shown to rapidly relieve dyspnea, reduce pulmonary arterial pressure and revascularize the embolized blood vessels. However, the hemorrhage rate of the thrombolysis group was higher than that of the anticoagulation group. The overall efficacies and fatality rates of the thrombolysis and anticoagulation groups were similar.