铁掺杂碳点作为过氧化物模拟酶用于谷胱甘肽检测研究

以芦丁、尿素和三氯化铁为原料,水热法合成了铁掺杂碳点(Fe-CDs),并对制备的Fe-CDs进行了透射电子显微镜、X-射线光电子能谱和傅里叶红外光谱的表征。Fe-CDs表面富含-COOH、-OH和-NH₂等含氧官能团,粒径主要分布在0.5～5 nm。Fe-CDs可催化H₂O₂氧化3,3’,5,5’-四甲基联苯胺,并在652 nm处出现较强的吸收峰。而谷胱甘肽(GSH)能还原ox-TMB使体系吸收峰强度降低。基于上述原理,建立了以Fe-CDs为过氧化物模拟酶的GSH测定方法。GSH浓度与体系吸收峰强度的变化值(ΔA)在2～30μmol·L^-1浓度范围内呈良好的线性关系,检出限为0.8μmol·L^-1。将该方法用于测定实际样品谷胱甘肽片的含量,加标回收率在98%～103%,RSD为1.4%～2.2%。结果表明,该方法能够用于实际样品谷胱甘肽片中GSH的含量测定。     

石墨烯量子点功能化金纳米粒子的制备及作为过氧化物模拟酶用于葡萄糖检测

基于石墨烯量子点（GQD）的还原性,在无需外加保护剂的条件下,采用一步法成功制备了稳定性高、分散性好的石墨烯量子点功能化的金纳米粒子（GQD@AuNPs）.所制备的GQD@AuNPs有优良的过氧化物模拟酶催化活性,能够有效地催化H₂O₂氧化3,3’,5,5’-四甲基联苯胺（TMB）产生显色反应.以TMB为模型底物,研究了催化条件（温度和pH）对催化活性的影响.电子自旋共振光谱（ESR）结果表明,GQD@AuNPs与辣根过氧化物酶（HRP）类似,能有效地催化H₂O₂分解成羟基自由基（^·OH）.基于此,结合葡萄糖在葡萄糖氧化酶（GOx）作用下产生H₂O₂的原理,建立了可视化检测血清中葡萄糖含量的简便方法.在优化条件下,本方法的检测范围为2.0×l0^-6～4.0×l0^-5 mol·L^-1,检出限为3.0×l0^-7 mol·L^-1,并对实际样品进行测定,测定结果与临床结果一致.     

基于碳量子点过氧化物模拟酶的肌氨酸比色测定

以果皮为原料制备了水溶性碳量子点(CQDs), 透射电子显微镜分析表明其平均粒径为2.4 nm; 红外光谱分析证实CQDs表面富含含氧官能团. 所得CQDs可催化H₂O₂氧化3,3',5,5'-四甲基联苯胺(TMB)生成蓝色氧化产物(ox-TMB). 基于上述反应, 建立了测定H₂O₂的分析方法, 在pH=3.5, 温度40 ℃, TMB浓度为1.0 mmol/L及孵育时间15 min的条件下, 当H₂O₂浓度在5.0~100 μmol/L范围时, ox-TMB的吸光度随H₂O₂浓度的升高而线 性增强, 方法的检出限为3.0 μmol/L. 鉴于H₂O₂是肌氨酸氧化酶催化肌氨酸氧化的产物之一, 建立了CQDs催化H₂O₂氧化TMB间接测定肌氨酸的分析方法. 结果表明, 当肌氨酸浓度在0.5~350 μmol/L范围内时, 吸光度 与其浓度呈良好的线性关系, 方法的检出限为0.3 μmol/L; 将该方法应用于人体尿样的测定, 回收率为94%~99%.     

用肌红蛋白作为过氧化物酶模拟酶光度测定葡萄糖

过氧化物酶(POD)由于活性高和选择性好常用于H202和葡萄糖(Glucose)含量的测定,但天然POD价格昂贵、易失活,实验条件和储存环境都很苛刻。肌红蛋白(Mb)是一种生物小分子,价格比POD低,实验条件温和,本实验将肌红蛋白作为过氧化物酶模拟酶催化H202氧化偶联还原型色原N-乙基-N-(2-羟基-3-磺酸基丙基)-3,5-二甲氧基苯胺(DAOS)和4-氨基安替比林(AAP)显色反应能用于H202的测定,     

石墨烯量子点-银纳米颗粒复合物用于过氧化氢和葡萄糖比色检测

以石墨烯量子点(GQDs)为还原剂和稳定剂,在其表面原位生长银纳米粒子(AgNPs),制备了具有良好分散性的GQDs/AgNPs纳米复合物,其粒径小于30 nm.GQDs/AgNPs纳米复合物具有类过氧化物酶的催化活性,能有效催化H2O2氧化3,3',5,5'-四甲基联苯胺(TMB)并发生显色反应.稳态动力学分析表明,GQDs/AgNPs催化动力学遵循典型的Michaelis-Menten模型,其催化机理符合乒乓机制.与辣根过氧化物酶(HRP)相比,GQDs/AgNPs纳米复合物具有更强的亲和性.基于GQDs/AgNPs的催化活性和葡萄糖氧化产生H2O2的原理,建立了H2O2和葡萄糖的比色检测方法,检出限分别为0.18和1.6 μmol/L.将本方法应用于血浆中葡萄糖的检测分析,结果与标准方法相符.     

废虾壳衍生多孔碳纳米酶的制备及用于比色检测自来水中过氧化氢

以废虾壳为碳源,通过惰性气氛高温碳化法制得废虾壳衍生的多孔碳纳米酶,并将其作为一种类过氧化物模拟酶用于比色检测自来水中的H₂O₂。所制备的碳纳米酶呈无定型多孔结构,且催化活性类似天然辣根过氧化物酶。考察了反应体系中各参数对类过氧化物酶催化活性的影响。在最优条件下,废虾壳衍生多孔碳纳米酶比色分析H₂O₂的线性范围为0～200μmol/L,线性相关系数R²=0.9772,检出限为0.59μmol/L。建立的方法可用于快速分析自来水中的H₂O₂。     

胶束增敏的辣根过氧化物酶催化荧光反应测定葡萄糖的研究

采用葡萄糖氧化酶－辣根过氧化物酶－对羟基苯丙酸－过氧化体系测定葡萄糖，阳离子胶束十六烷基三甲基溴化铵对生荧反应具有催化和增敏作用，可用于１μ１样品中葡萄糖的测定，线性范围０．５－５０μｇ，线性相关系数ｒ＝０．９９６６，相对标准偏差为０．７３％，检测限为０．４６μｇ。     

基于二氧化锰-氧掺杂氮化碳级联催化的无酶比色检测葡萄糖研究

基于二氧化锰(MnO₂)-氧掺杂氮化碳(OCN)复合材料,构建了一种级联催化无酶比色葡萄糖传感器。通过在OCN的分散液中化学沉淀MnO₂晶体制备得到MnO₂-OCN复合材料。单体MnO₂具有优异的类葡萄糖氧化酶活性,能够催化葡萄糖分解产生H₂O₂,但类过氧化物酶活性较弱,无法充分消耗反应产生的H₂O₂。通过引入OCN,利用其优异的类过氧化物酶活性,可以显著促进H₂O₂对底物的催化氧化,使溶液变色,显著改善了对葡萄糖的检测性能。基于MnO₂-OCN复合材料构建的无酶比色传感器拥有较宽的检测范围(0.05～2.00 mmol/L),检出限为23μmol/L(S/N=3)。将此传感器用于血清样品中葡萄糖的检测,加标回收率为91.9%～94.3%。由于MnO₂和OCN两种材料对底物有较强的专一性,此传感器特异性识别催化葡萄糖,特异性良...     

NEWS——CdTe量子点/过氧化物酶体系用于灵敏检测酚类化合物和过氧化氢

半导体纳米粒子（量子点,quantum dots,QDs）由于其独特的电子量子限域及尺寸相关的荧光发射性质,已经在电子学,发光装置和生物分析领域中引起了广泛的的兴趣。发展基于QDs的化学及生物分析尤其是传感器是分析化学领域的前沿之一。由于量子点的荧光对其表面非常敏感,物质与量子点表面的相互作用可能会导致荧光的变化;研究发现,电子／空穴受体（如苯醌、对苯胺等）会猝灭量子点的荧光。     

Carbon dots from tryptophan doped glucose for peroxynitrite sensing

Tryptophan doped carbon dots (Trp-CD) were microwave synthesized. The optimum conditions of synthesizing of the Trp-CD were established by response surface multivariate optimization methodologies and were the following: 2.5 g of glucose and 300 mg of tryptophan diluted in 15 mL of water exposed for 5 min to a microwave radiation of 700 W. Trp-CD have an average size of 20 nm, were fluorescent with a quantum yield of 12.4% and the presence of peroxynitrite anion (ONOO⁻) provokes quenching of the fluorescence. The evaluated analytical methodology for ONOO⁻ detection shows a linear response range from 5 to 25 μM with a limit of detection of 1.5 μM and quantification of 4.9 μM. The capability of the ONOO⁻ quantification was evaluated in standard solutions and in fortified serum samples.     

Smartphone-based colorimetric determination of glucose in food samples based on the intrinsic peroxidase-like activity of nitrogen-doped carbon dots obtained from locusts

In this study, nitrogen-doped carbon dots (N-CDs) with excellent peroxidase-like activity were prepared using locust powder as the carbon source by a self-exothermic reaction. The obtained N-CDs could catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂ to generate a blue oxidized product (TMB_ox) with a maximum absorption peak at 654 nm. The catalytic reaction conditions were optimized; furthermore, steady-state kinetic analysis indicated that N-CDs exhibited high affinity toward both TMB and H₂O₂, and the Michaelis-Menten constant (k_m) values were 0.115 mM (TMB) and 0.764 mM (H₂O₂). A smartphone-based colorimetric method was developed for quantitative detection. The 1/L values (L stands for lightness in HSL color space) of the TMB_ox solution were recorded via an iPhone application Color Analyzer. Since H₂O₂ is the by-product of glucose (Glu) oxidation in the presence of glucose oxidase (GOx), a simple, sensitive, and selective smartphone-based colorimetric method was developed for the determination of Glu, and the detection limit was 1.09 μM. The smartphone-based method was successfully applied to determine Glu in different food samples with recoveries in the range of 88.5–109.0 %.     

二氧化铈纳米微粒过氧化物酶活性及其在葡萄糖检测中的应用

合成了一种稳定和水溶性的聚丙烯酸修饰CeO2 NPs,利用动态光散射(DLS)、傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)进行表征.结果表明,CeO2 NPs能够催化H2O2氧化3,3′,5,5′-四甲基联苯胺(TMB)发生显色反应,表现出过氧化物模拟酶催化活性.利用Raman和顺磁共振(EPR)光谱技术研究了其催化机理.基于CeO2 NPs催化TMB变色反应对H2O2浓度的依赖性和葡萄糖氧化酶能够催化溶解氧氧化葡萄糖产生H2O2的原理,构建了一种简单、灵敏、选择性高的测定血清中葡萄糖的检测方法.在优化条件下,测定葡萄糖的线性范围为0.5~10 mmol/L,检出限(3σ)为0.1 mmol/L.对1.0 mmol/L葡萄糖进行11次平行测定,其相对标准偏差为2.4%.该方法已成功用于血清样品中葡萄糖的测定.     

Intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and their application in the colorimetric detection of H2O2 and glucose

In this paper, the highly intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots (N-GQDs) is revealed. This activity was greatly dependent on pH, temperature and H₂O₂ concentration. The experimental results showed that the stable N-GQDs could be used for the detection of H₂O₂ and glucose over a wide range of pH and temperature, offering a simple, highly selective and sensitive approach for their colorimetric sensing. The linearity between the analyte concentration and absorption ranged from 20 to 1170 μM for H₂O₂ and 25 to 375 μM for glucose with a detection limit of 5.3 μM for H₂O₂ and 16 μM for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples.     

Glutathione-capped CdTe quantum dots for the sensitive detection of glucose

A simple and sensitive assay system for glucose based on the glutathione (GSH)-capped CdTe quantum dots (QDs) was developed. GSH-capped CdTe QDs exhibit higher sensitivity to H₂O₂ produced from the glucose oxidase catalyzed oxidation of glucose, and are also more biocompatible than other thiols-capped QDs. Based on the quenching of H₂O₂ on GSH-capped QDs, glucose can be detected. The detection conditions containing reaction time, the concentration of glucose oxidase and the sizes of QDs were optimized and the detection limits for glucose was determined to be 0.1 μM; two detection ranges of glucose from 1.0 μM to 0.5 mM and from 1.0 mM to 20 mM, respectively were obtained. The detection limit was almost a 1000 times lower than other QDs-based optical glucose sensing systems. The developed glucose detection system was simple and facile with no need of complicated enzyme immobilization and modification of QDs.     

Defect-rich and ultrathin nitrogen-doped carbon nanosheets with enhanced peroxidase-like activity for the detection of urease activity and fluoride ion

Although carbon nanozymes have attracted great interest due to their good biocompatibility, low cost,and high stability, designing high-active carbon nanozymes still faces great challenges. Herein, ultrathin nitrogen-doped carbon nanosheets with rich defects(d-NC) were prepared through a high-temperature annealing process, using potassium chloride and ammonium chloride as templates. Owing to the large specific surface area, rich defects and the high exposure of active sites, the proposed d-NC na...     

Catalytic and peroxidase-like activity of carbon based-AuPd bimetallic nanocomposite produced using carbon dots as the reductant

In this report, carbon-based AuPd bimetallic nanocomposite (AuPd/C NC) was synthesized using carbon dots (C-dots) as the reducing agent and stabilizer by a simple green sequential reduction strategy, without adding other agents. The as synthesized AuPd/C NC showed good catalytic activity and peroxidase-like property. The structure and morphology of these nanoparticles were clearly characterized by UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The AuPd/C NC catalyst exhibits noticeably higher catalytic activity than Pd and Au nanoparticles in catalysis reduction of 4-nitrophenol (4-NP). Moreover, based on the high peroxidase-like property of AuPd/C NC, a new colorimetric detection method for hydrogen peroxide (H₂O₂) has been designed using 3,3′,5,5′-tetramethyl-benzidine (TMB) as the substrate, which provides a simple and sensitive means to detect H₂O₂ in wide linear range of 5 μM–500 μM and 500 μM–4 mM with low detection limit of 1.6 μM (S/N = 3). Therefore, the facile synthesis strategy for bimetallic nanoparticles by the mild reductant of carbon dot will provide some new thoughts for preparing of carbon-based metal nanomaterials and expand their application in catalysis and analytical chemistry areas.     

A heme-peptide metalloenzyme mimetic with natural peroxidase-like activity

Mimicking enzymes with alternative molecules represents an important objective in synthetic biology, aimed to obtain new chemical entities for specific applications. This objective is hampered by the large size and complexity of enzymes. The manipulation of their structures often leads to a reduction of enzyme activity. Herein, we describe the spectroscopic and functional characterization of Fe(III)-mimochrome VI, a 3.5 kDa synthetic heme-protein model, which displays a peroxidase-like catalytic activity. By the use of hydrogen peroxide, Fe(III)-mimochrome VI efficiently catalyzes the oxidation of several substrates, with a typical Michaelis-Menten mechanism and with several multiple turnovers. The catalytic efficiency of Fe(III)-mimochrome VI in the oxidation of 2,2'-azino-di(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and guaiacol (k(cat)/K(m)=4417 and 870 mM(-1) s(-1), respectively) is comparable to that of native horseradish peroxidase (HRP, k(cat)/K(m)=5125 and 500 mM(-1) s(-1), respectively). Fe(III)-mimochrome VI also converts phenol to 4- and 2-nitrophenol in the presence of NO(2) (-) and H(2) O(2) in high yields. These results demonstrate that small synthetic peptides can impart high enzyme activities to metal cofactors, and anticipate the possibility of constructing new biocatalysts tailored to specific functions.     

Direct electrochemical detection of kanamycin based on peroxidase-like activity of gold nanoparticles

An enzyme-free, ultrasensitive electrochemical detection of kanamycin residue was achieved based on mimetic peroxidase activity of gold nanoparticles (AuNPs) and target-induced replacement of the aptamer. AuNPs which were synthesized using tyrosine as a reducing and capping agent, exhibited mimetic peroxidase activity. In the presence of kanamycin-specific aptamer, however, the single-stranded DNA (ssDNA) adsorbed on the surface of AuNPs via the interaction between the bases of ssDNA and AuNPs, and therefore blocked the catalytic site of AuNPs, and inhibited their peroxidase activity. While in the presence of target kanamycin, it bound with the adsorbed aptamer on AuNPs with high affinity, exposed the surface of AuNPs and recovered the peroxidase activity. Then AuNPs catalyzed the reaction between H₂O₂ and reduced thionine to produce oxidized thionine. The latter exhibited a distinct reduction peak on gold electrode in differential pulse voltammetry (DPV), and could be utilized to quantify the concentration of kanamycin. Under the optimized conditions, the proposed electrochemical assay showed an extremely high sensitivity towards kanamycin, with a linear relationship between the peak current and the concentration of kanamycin in the range of 0.1–60 nM, and a detection limit of 0.06 nM. Moreover, the established approach was successfully applied in the detection of kanamycin in honey samples. Therefore, the proposed electrochemical assay has great potential in the fields of food quality control and environmental monitoring.     

Intrinsically fluorescent carbon dots with tunable emission derived from hydrothermal treatment of glucose in the presence of monopotassium phosphate

A facile method is developed to synthesize intrinsically fluorescent carbon dots by hydrothermal treatment of glucose in the presence of monopotassium phosphate. The fluorescence emission of the carbon dots thus produced is tunable by simply adjusting the concentration of monopotassium phosphate.