Clinically, patients with gout are often treated with uricase (Uox)-based drugs. While these medications are effective, many patients suffer from immune rejection associated with their use. To reduce Uox's immunogenicity, it was modified with carbon dots synthesized from citric acid and ethylenediamine (CA/EDA-CDs), forming CA/EDA-Uox. The particle size, zeta potential, and main functional groups of CA/EDA-CDs and CA/EDA-Uox were characterized by transmission electron microscopy (TEM), FT-IR, and dynamic light scattering (DLS). CCK8 and flow cytometry were used to detect the survival rate of L02 cells treated with CA/EDA-CDs and CA/EDA-Uox, respectively. After treatment with 1% CA/EDA-Uox for 2 weeks, IgG and IgM titers in rats were detected by ELISA. The particle size of CA/EDA-CDs is mainly 5 nm, and zeta potential is distributed in -10.3 mV and 5.8 mV. The cell survival rate and the number of fluorescently labeled cells were the highest in 1% CA/EDA-CDs and 1% CA/EDA-Uox treatment groups, respectively. No antibody was detected in 1% CA/EDA-Uox treated rats. The contents of IL-2, 6, 10, and TNF-β in the blood of quails were significantly lower than those in Uox group (p < 0.01). The cytotoxicity of 1% CA/EDA-CDs and 1% CA/EDA-Uox were the lowest; there were less antibodies produced by 1% CA/EDA-Uox in rats. CA/EDA-Uox exhibits satisfactory safety, low immunogenicity, and favorable pharmacological properties. It holds promise for progression to the clinical trials and eventual clinical application.

Background: Uricase (Uox) is a major drug in gout and a supplementary drug in cancer treatment. Because allergic reactions caused by Uox limit its clinical application,10% Co/EDTA was used to chemically modify Uox from A. flavus to reduce its immunogenicity. Methods: The immunogenicity of Uox and 10% Co/EDTA-Uox was examined by determining the antibody titer and concentration of IL-2, IL-6, IL-10, and TNF-β in quail and rat serum. Moreover, we examined the pharmacokinetics of 10% Co/EDTA-Uox in rats and acute toxicity in mice. Results: The concentration of UA decreased from 771.85 ± 180.99 to 299.47 ± 20.37 μmoL/L (p<0.01) in the hyperuricemia model of quails injected by 10% Co/EDTA-Uox. Two-way immuno- diffusion electrophoresis revealed that 10% Co/EDTA-Uox did not produce antibody, whereas the antibody titer against Uox was 1:16. The concentrations of four cytokines in the 10% Co/EDTA-Uox group were significantly lower than in Uox group (p < 0.01); The titer of IgG and IgM against 10% Co/EDTA-Uox was significantly lower than that against Uox at different serum dilutions (p < 0.0001). The pharmacokinetic data indicated that the half-life time of 10% Co/EDTA- Uox (69.315 h) was significantly longer than that of Uox (13.4 h) (p<0.01). The tissue section of the liver, heart, kidney, and spleen revealed no toxicity in Uox and 10% Co/EDTA- Uox groups. Conclusion: 10% Co/EDTA-Uox possesses little immunogenicity, a long half-life time, and a highly efficient degradation of UA.

Cascade reactions catalyzed by natural uricase and mimic peroxidase (MPOD) have been applied for uric acid (UA) detection. However, the optimal catalytic activity of MPOD is mostly in acidic conditions (pH 2-5), mis-matching the optimal catalytic alkaline environment of uricase. In this paper, using CuSO4 and urea as raw materials, a MPOD with high catalytic activity in alkaline environment was synthesized by hydrothermal method. Then, based on coupling reaction of uricase/UA/MPOD/guaiacol (GA) system, a novel spectrophoto-metric method was established to detect 5-60 mu mol/L UA (limit of detection = 3.14 mu mol/L (S/N = 3)) and accurately quantified serum UA (275.6 +/- 39.9 mu mol/L, n = 5) with 95-105% of standard addition recovery. The results were consistent with commercial UA kit (p > 0.05). The MPOD could replace natural POD to reduce the cost of UA detection due to simple preparation and cheap raw materials, and is expected to achieve the specific detection of some substances, like glucose and cholesterol, combined with glucose oxidase and cholesterol oxidase.

Development of a highly sensitive, reusable, and micro-portable sensor for chemical oxygen demand (COD) determination is significantly important for in-situ measurements. In this paper, a reusable carbon-dots fluorescence capillary sensor is reported. Based the sol-gel technology, citric acid/urea-carbon dots synthesized by the hydrothermal treatment were immobilized on the inner surface of the capillary, and combined with the recirculating-flow system, a new sensor method was established for enriching and determining COD in water. On the basis of the mechanism that MnO2, reaction product of KMnO4 reduced by carbon dots, quenches the fluorescence of the sensor through adsorption/inner filter effect, we successfully determined CODMn (permanganate index) in the range of 0.2-40 mg L-1 (ΔF = -48.32c + 678.25, r = 0.9996,0.2-12 mg L-1;ΔF = -16.31c + 792.61, r = 0.9998,8-40 mg L-1); and then, regeneration of the sensor was conducted by using ascorbic acid to reduce carbon dots and remove the effect of MnO2 adsorbed on the inner surface, as thus, the sensor can be reused at least 20 times with the relative standard deviation less than 0.59%. The method has been applied to the quantification of COD in potable, waste and natural water. Combined with the automatic system, it will be a potential method for in-situ real-time monitoring of COD in water.

The interaction mechanism between carbon dots (CDs) and metal ions is essential for optimizing their design, synthesis, and application. However, it must be accurately distinguished and quantified because of CDs' complex structure, composition, and coexisting various response mechanisms or products. Herein, a recirculating-flow fluorescence capillary analysis (RF-FCA) system was developed to online monitor the fluorescence kinetics of CDs interacting with metal ions. The fluorescence kinetics of purification and dissociation of CDs/metal ion complexes were easy to monitor online by integrating immobilized CDs and RF-FCA. Here, CDs derived from citric acid and ethylenediamine were used as a model system. We found that the fluorescence of CDs is quenched by Cu(II) and Hg(II) only through the formation of a coordination complex, by Cr(VI) only through the inner filtering effect, and by Fe(III) through the above two mechanisms. Then the kinetics of the competitive interaction between metal ions were used to address the difference of binding sites on CDs with metal ions, wherein Hg(II) was bound to other sites of CDs besides the same sites of CDs with Fe(III) and Cu(II). Finally, from the fluorescence kinetics of fluorescent molecules in the CD structure with metal ions, the difference was due to the presence of two fluorescent centers in the carbon core and molecular state in the CDs. Therefore, the RF-FCA system can distinguish and quantify the interaction mechanism between metal ions and CDs effectively and accurately and be a potential detection or performance characterization method.

In using a flow-injection recirculating-catalysis system developed by us to research the simultaneous quantification for peroxidase and ascorbate, it was discovered that the concentrations of peroxidase activity and ascorbate are correlative with the slope and the negative intercept of the linear response curve during a peroxidase-catalyzed kinetic course. Therefore, based on this finding, a new analytical method and a simplified equation for quantifying the peroxidase activity concentration were proposed, Then, test conditions were optimized, finally the use of the method has realized the simultaneous determination for peroxidase of 2-40 U/L and ascorbate of 0.4-12 mg/L in various vegetables (60 μL). The assayed results were consistent with the comparison method, in which the repeatability (RSD < 1.43%, n = 11) was satisfactory. Another important conclusion obtained in this study is that the determination of the peroxidase activity in biosamples must use the kinetic curve method for fear of the influence from the ascorbate's lag phase.

利用(3-氨丙基)三乙氧基硅烷和柠檬酸合成了一种硅、氮共掺杂的高量子产率的荧光碳点(SiN-CDs).Hg(Ⅱ)能静态猝灭SiN-CDs在455 nm处的荧光(λex=370 nm),据此建立了一种荧光猝灭测定Hg(Ⅱ)的方法.在pH为7的醋酸盐缓冲溶液中,0.005～6 μmol/L的Hg(Ⅱ)与荧光猝灭值(AF)呈线性关系,检测限(3σ/k)为3.33 nmol/L,低于世界卫生组织饮用水中Hg(Ⅱ)的指导值.标准加入法测定环境水样中Hg(Ⅱ)含量,其加标回收率为92％～105％,测定值的相对标准偏差(RSD)为0.50％～4.53％.

将柠檬酸/乙二胺荧光碳点(CDs)通过与γ-氨丙基三乙氧基硅烷(KH550)的交联反应修饰在玻璃毛细管的内表面,开发了一种新的固定化碳点荧光毛细传感器(CDs-FCAS).基于CDs与Cr(Ⅵ)之间的荧光猝灭反应,用于Cr(Ⅵ)含量的在线检测;并用PBS对反应后的传感器进行清洗,恢复传感器的荧光,实现了 CDs-FCAS的重复利用.传感器荧光稳定性良好(RSD＜3.5％).对测定条件进行了优化:反应溶液pH 8.0、泵流量为1 mL/min.CDs-FCAS测定Cr(Ⅵ)的线性范围为0.1～2.0 mg/L,检出限为0.05 mg/L.该方法成功用于环境水中Cr(Ⅵ)的测定,回收率为95.1％～104.7％.

以柠檬酸、乙二胺、水杨酸和Fe(Ⅲ)为原料,合成了一种对氟离子特异性响应的复合荧光碳点(RCDs-Fe(Ⅲ)).随后通过一系列实验,对碳点合成和氟离子检测条件进行了优化.结果表明,碳点合成最优原料配比为2 mL乙二胺、2 g柠檬酸和0.2 g水杨酸;最优检测条件:反应体系溶剂为pH 5.0的盐酸溶液,Fe(Ⅲ)浓度为150 mg/L,复合碳点浓度为0.5％,碳点激发与发射波长分别为370,460 nm.在最优检测条件下,RCDs-Fe(Ⅲ)检测氟离子的线性范围为1～25 mg/L,检出限为0.82 mg/L.复合碳点测定牙膏中氟离子的结果与对比法一致.

In the research of carbon dots (CDs) containing various nitrogen sources, it was first found that urea/citric acid-CDs showed a selective discolouration reaction with sulphide ions. Therefore, by optimizing various synthesis and detection conditions of the CDs determining sulfur ions, such as the raw material ratio, temperature, time, pH, and oxidation atmosphere in the CD synthesis, a discolour CD-probe method for trace-level sulphide ions was developed. The method is environmentally friendly, shows two linear-response ranges in 0.050-1.0 mg L-1 (A = -0.0827c + 0.8366) and 1.0-15 mg L-1 S2- (A = -0.0209c + 0.7587) and can be used for the high and low concentration quantification of sulphide in various wastewaters. Subsequently, in order to realize the separation and detection of sulphide ions in wastewaters or rich- and barren-liquids containing N-methyldiethanolamine and other substances in desulphurizing solutions, an automatic pretreatment system was also established.

A new fluorescence probe method for the detection of Hg(II) in serum was established, which has the detection limit of 3.57 nM and quantification limit of 5 nM, based on the electrostatic induced agglomeration quenching and complexation between Hg(II) and silicon-nitrogen-doped carbon nanodots (Si/N-CDs). Furthermore, the fluorescence probe also showed the satisfactory results in the determination of Hg (II) in human serum. Subsequently, take advantage of the uric acid (UA) to recover the fluorescence of the Si/N-CDs-Hg(II) complex probe, another enzyme-free ways to determine UA was developed. The complex probe can selectively detect the UA content in the 0.5-30 mu M range, and its detection limit can reach 0.14 mu M, which has successfully detected the UA in total serum, and the results were no significant difference comparing with the controls. (C) 2021 Elsevier B.V. All rights reserved.

Herein, cobalt and nitrogen co-doped carbon dots (Co-N-CDs) were fabricated via a one-pot hydrothermal approach. The obtained Co-N-CDs displayed peroxidase-like activity and fluorescence properties. It could catalyze the oxidization of guaiacol (GA) in the presence of hydrogen peroxide (H2O2), and thus, resulted in color change, accompanied by a new absorption peak in 470 nm. Owing to the inner filter effect, the oxidized product of GA (known as 2-PQ) largely absorbed the Co-N-CD fluorescence which was excited at 380 nm. Such changes in absorbance and fluorescence intensity were H2O2 concentration-dependent. Specifically, H2O2 could be generated by glucose oxidase to catalyze the oxidation of glucose, and thus, a colorimetric and fluorimetric sensor for glucose was established with high selectivity and excellent sensitivity. After the optimization of experimental conditions, this colorimetric sensor has a good linear range from 2 to 100 μM for glucose and the detection limit was 1.16 μM. Besides, the linear relationship between the fluorescence quenching value (ΔF) and the glucose concentration (0.4-40 μM) was obtained with a detection limit of 0.18 μM. Meanwhile, the proposed sensor has also been successfully applied for glucose detection in human serum samples, and the results were consistent with those of the standard method.

利用柠檬酸(CA)为碳源,乙二胺(EDA)为氮源通过微波加热法合成柠檬酸/乙二胺碳点(CA/EDA-CQDs).采用静电结合法,将CA/EDA-CQDs固定在毛细管内表面,制备了一种荧光传感器.考察了CA/EDA-CQDs与聚丙烯酸(PAA)溶液浓度、pH对固定化影响.优化的固定化条件为:CA/EDA-CQDs浓度为15 mg/L,pH为3,PAA浓度为6 mg/L,pH为3.制备的传感器对Fe3+有特异性响应.

To evaluate the grain size and particle number formed in a non-equilibrium flow mixing state, flow-injection analysis (FIA) was combined with focused beam reflectance measurement (FBRM). The influence of BaCl2, PEG-4000, ethanol, flowrate, temperature and acidity on the dynamic formation of BaSO4 particles was evaluated. Optimization parameters obtained were 5% BaCl2 as the reagent, 2% PEG-4000 + 6% ethanol as the stabilizer and 0.3 mol L-1 HCl as the carrier with 4 ml min-1 flowrate, and the BaSO4 particle size distribution in the system was in the 1-50 μm range. Under optimized conditions, the system was successfully used for the determination of high sulfate concentrations in the wet-process phosphoric acid process in the 3.2-48 g L-1 (Sct = 55c + 208, r = 0.998, n = 3) range for SO42-. The relative standard deviation was less than 1.86% (n = 11), the detection limit was 0.95 g L-1, the sample throughput reached 30 samples per h, recovery data were within the 97-106% range, and the results were consistent with those of gravimetry (RD < 3%). The system avoids the large error caused by high dilution and the slow analysis speed when measuring high sulfate concentrations.

基于愈创木酚(GA)/过氧化物酶(POD)/过氧化氢(H2O2)反应体系,建立一种新的流动注射分析流路,测定多种植物样品中过氧化物酶活性.结果表明,系统参数优化如下:系统流速1.91 mL/min,样品进样体积40μL,试剂注入体积150μL,反应盘管长度150 cm,磷酸盐缓冲溶液浓度0.05 mol/L,pH 6.0;HCl清洗液进样体积150μL,浓度0.24 mol/L;底物为4.5 mmol/L GA和1.5 mmol/L H2 O2混合溶液;反应产物的表观摩尔吸光系数测定结果为0.0064 L/(μmol·cm).本方法测定范围在153～2752 U/L之间,检出限为25.7 U/L,重现性较好(RSD≤3.38％,n=11),分析速度为90样/h.对五种植物样品中的过氧化物酶活性测定并进行加标回收实验,回收率在95％ ～105％之间.

采用磷钼酸光度法自动快速分析湿法磷酸中超高浓度P2O5(3～200 g/L)含量,考察了显色剂浓度、酸度、反应盘管RC长度、稀释盘管DC长度、温度等对P2 O5测定的影响.优化的测试条件为:反应试剂由15 mmol/L钼酸铵、9 mmol/L偏钒酸铵及0.7 mol/L HNO3构成,RC为25 cm,DC2为500 cm.结果表明,本方法的直接测定P2O5的范围达到了工业生产的控制要求(3～200 g/L P2O5),重现性较好(RSD≤0.63％,n=11),分析速度为20样/h,实样加标回收率在98％～104％,测定结果与喹钼柠酮重量法一致,而且不会受到湿法磷酸生产中共存的高浓度SO2-4、F-的干扰.

In this paper, an ultrasensitive and rapid "turn-on" fluorescence sensor, integrating flow-injection (FI) with nitrogen-doped carbon dots/gold nanoparticles (N-CDs/AuNPs) double-probe is established for the determination of metformin hydrochloride (MET) in biological fluids. The sensing strategy involves the weak inner filter effect between AuNPs and N-CDs due to aggregation products of MET with AuNPs. Unfortunately, the degree of AuNPs aggregation is difficult to control through manual assays, resulting in intolerable measurement error that limits further applications. However, the proposed method overcomes the above problem, and significantly lowers the consumption of expensive reagents (AuNPs: about 60 lL per test). Under optimal conditions, the fluorescence intensity at 400 nm excitation and 505 nm emission wavelengths display a linear correlation with MET concentration (5-100 mu g L-1) and the limit of detection is 2.32 mu g L-1 (3.3 S/k). The advantages of the presented method include high sensitivity, rapid speed (60 sample h(-1)), good accuracy and precision (RSD <= 2.1%, n = 11) and low cost. Since MET is the first-line hypoglycemic agent in patients with type II diabetes, this method can preliminarily determine MET content in urine samples, giving satisfactory results. (C) 2020 Elsevier B.V. All rights reserved.

The use of a recirculating-flow catalysis detection system (RFCD) explored competition and the influence of ascorbic acid (AsA) in peroxidase (POD)-catalyzed reactions. The study identified that AsA is neither the inhibitor of POD nor could directly deplete H2O2; it directly reacts with chromogenic products to form colorless intermediates, which can react with H2O2 to again rapidly re-generate the chromogenic products. If using the reactions (trinder reactions or enzyme-linked reactions) to determine POD activity (EPOD), substrates or analytes, the interference of concomitant AsA should be removed and the conclusions have significance for oxidase/POD catalyzed reactions. In addition, the RFCD system was also used to simultaneously determine EPOD and AsA.

为了解决湿法磷酸生产中高含量SO3的测定,对硫酸钡浊度测定法的反应条件进行了改进,并自行设计制造了自动化的分析系统.测定时样品由蠕动泵(P)推入酸化盘管(AC)中进行酸化和稀释,由定量环(Sv)取样25μL,注入反应系统.在第一反应盘管(RC1)中,SO3与第一混合试剂中的BaCl2溶液反应生成BaSO4悬浊液,该溶液中的聚乙二醇-4000(PEG-4000)和乙醇通过协同作用避免了BaSO4颗粒的团聚,降低粒子间的相互作用,使BaSO4的生成减少,降低了测定的灵敏度,提高了稳定性.在第二反应盘管(RC2)中,BaSO4与第二混合试剂中的NH3·H2O/乙二胺四乙酸二钠(Na2 EDTA)溶液发生络合反应同时被Na2 EDTA包裹,进一步降低其灵敏度.最后反应溶液进入流通式光度检测器,在680.0 nm波长处测试BaSO4悬浊液的吸光度.经优化试验条件,上述第一混合试剂中3种组分的质量分数或体积分数为:BaCl24％,PEG-40003％和乙醇2％;第二混合试剂中Na2 EDTA的质量分数为6％,NH3·H2 O的体积分数为6％.对实际按本方法及重量法分析进行测定,两种方法所得结果的相对偏差在±2％以内,且不受共存的高含量PO43-和F-的干扰.

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.