Fruit waste (Pulp) decorated CuO NFs as promising platform for enhanced catalytic response and its peroxidase mimics evaluation

Herein, we report for the first time, an eco-compatible hydrothermal route for the synthesis of carbon enriched mesoporous material (CuO NFs@MP) using fruit waste (Pulp) obtained from Citrus limetta’s (Mausambi) decorated irregular shaped CuO nanoflakes (NFs). The CuO NFs@MP nanocomposite was fully characterized through several spectroscopic-cum-analytical techniques such as TEM and XPS, which further confirmed the presence of CuO NFs. CuO NFs@MP could serve as an excellent catalyst for N-Arylation reaction and also paves promising peroxidase mimic activity. The preliminary results indicated that CuO NFs@MP shows the catalytic advantage of higher yields, shorter reaction time and greener conditions. Simultaneously, the oxidation of colorless TMB with H₂O₂ into blue-green colored ox-TMB was also observed in 60 s with CuO NFs@MP. The present nanocomposite is easy to synthesize, economical, retrievable and a reusable catalyst for synthesizing a varied range of N-Arylated products and could also mimic peroxidase without significant loss of activity.     

Antioxidant and Prooxidant Nanozymes: From Cellular Redox Regulation to Next-Generation Therapeutics

Nanozymes, nanomaterials with enzyme-mimicking activity, have attracted tremendous interest in recent years owing to their ability to replace natural enzymes in various biomedical applications, such as biosensing, therapeutics, drug delivery, and bioimaging. In particular, the nanozymes capable of regulating the cellular redox status by mimicking the antioxidant enzymes in mammalian cells are of great therapeutic significance in oxidative-stress-mediated disorders. As the distinction of physiological oxidative stress (oxidative eustress) and pathological oxidative stress (oxidative distress) occurs at a fine borderline, it is a great challenge to design nanozymes that can differentially sense the two extremes in cells, tissues and organs and mediate appropriate redox chemical reactions. In this Review, we summarize the advances in the development of redox-active nanozymes and their biomedical applications. We primarily highlight the therapeutic significance of the antioxidant and prooxidant nanozymes in various disease model systems, such as cancer, neurodegeneration, and cardiovascular diseases. The future perspectives of this emerging area of research and the challenges associated with the biomedical applications of nanozymes are described.     

Blue-LED Synthesis of Pummerer's Ketones by Peroxidase-Lignin-Catalyzed Oxidative Coupling of Substituted Phenols

Pummerer's ketones resembling the tricyclic scaffold of bioactive natural substances were synthesized by blue-LED driven Horseradish Peroxidase oxidative coupling of substituted phenols in 2-methyltetrahydrofuran by using meso-tetraphenylporphyrin as photosensitizer and dioxygen as primary oxidant. The application of functionalized lignin nanoparticles as a renewable and efficient platform for the immobilization of the enzyme extended the effectiveness of the overall process to heterogeneous catalysis under buffer limiting conditions.     

基于愈创木酚荧光减量准确测定过氧化物酶活性的新方法

利用H2O2/过氧化物酶(POD)/愈创木酚(GA)反应体系的产物(470 nm)吸光度去定量POD活性是目前常用方法之一,但产物不稳定且对比色皿有吸附现象是该反应的主要缺点之一。为了解决此问题,本研究利用GA的荧光特性建立了一种能准确测定POD活性的方法。用辣根过氧化物酶( HRP)作为测试样品得到了以下优化条件：0.5 mmol/L GA,0.5 mmol/L H2O2,0.05 mol/L PBS缓冲液(pH 6.0),反应温度20℃,样品耗量20μL;本方法的线性范围为500~60000 U/L(r=0.9993),RSD≤2.4%(n=11),检出限为385 U/L。在优化条件下,用白萝卜提取液作为测试样品,用本方法((9714依132) U/L)与比色法((9926依352) U/L)和循环催化流动分析法((9608依456) U/L)进行了对比,结果表明,3种方法相互一致性很好。     

Revisiting catechol derivatives as robust chromogenic hydrogen donors working in alkaline media for peroxidase mimetics

Colloidal noble metal-based nanoparticles are able to catalyze oxidation of chromogenic substrates by H₂O_2, similarly to peroxidases, even in basic media. However, lack of robust chromogens, which work in high pH impedes their real applications. Herein we demonstrate the applicability of selected catechol derivatives: bromopyrogallol red (BPR) and pyrogallol (PG) as chromogenic substrates for peroxidase-like activity assays, which are capable of working over wide range of pH, covering also basic values. Hyperbranched polyglycidol-stabilized gold nanoparticles (HBPG@AuNPs) were used as model enzyme mimetics. Efficiency of several methods of improving stability of substrates in alkaline media by means of selective suppression of their autoxidation by molecular oxygen was evaluated. In a framework of presented studies the impact of borate anion, applied as complexing agent for PG and BPR, on their stability and reactivity towards oxidation mediated by catalytic AuNPs was investigated. The key role of high concentration of hydrogen peroxide in elimination of non-catalytic oxidation of PG and improvement of optical properties of BPR in alkaline media containing borate was underlined. Described methods of peroxidase-like activity characterization with the use of BPR and PG can become universal tools for characterization of nanozymes, which gain various applications, among others, they are used as catalytic labels in bioassays and biosensors.     

Amperometric biosensor based on reductive H2O2 detection using pentacyanoferrate-bound polymer for creatinine determination

Pentacyanoferrate-bound poly(1-vinylimidazole) (PVI[Fe(CN)₅]) was selected as a mediator for amperometric creatinine determination based on the reductive H₂O₂ detection. Creatinine amidohydrolase (CNH), creatine amidohydrolase (CRH), sarcosine oxidase (SOD), peroxidase (POD), and PVI[Fe(CN)₅] were crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) on a glassy carbon (GC) electrode for a creatinine biosensor fabrication. Reduction current was monitored at −0.1 V in the presence of creatinine and O₂. It is revealed that PVI[Fe(CN)₅] is suitable as a mediator for a bioelectrocatalytic reaction of POD, since PVI[Fe(CN)₅] neither reacts with reactants nor works as an electron acceptor of SOD. The amounts of PVI[Fe(CN)₅], PEGDGE, and enzymes were optimized toward creatinine detection. Nafion as a protecting film successfully prevented the enzyme layer from interferences. The detection limit and linear range in creatinine determination were 12 μM and 12–500 μM (R² = 0.993), respectively, and the sensitivity was 11 mA cm⁻² M⁻¹, which is applicable for urine creatinine tests. The results of the creatinine determination for four urine samples measured with this proposed method were compared with Jaffe method, and a good correlation was obtained between the results.     

The Effect of Selenium Supplementation on the NMR Proton Relaxation Time T1 in Plasma

Selenium has been identified as an essential dietary trace e1ementQ)which is a component of glutathione peroxidase (GSH-Px)(₂)and a cytochrome C-like protein(₃), The enzyme,the four subunits of which each contain one atom of selenium in the form of selenocysteine, the selenium containing active centre being amenable to chemical modification, catalyses the reduction of H,O,and organic hydroperoxides to water.In this way GSH-Px plays an important role in the protection of the cell from oxidative stresses such as the superoxide anion,organic hydroperoxides and H₂O₂     

Ni,Ru掺杂CePO4纳米材料的合成与仿酶性质

通过水热方法合成了具有高比表面积的Ni, Ru掺杂CePO₄纳米粒子(NiRu-CePO₄). 结合纳米粒子的X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和X射线能谱(EDX)的表征结果发现, NiRu-CePO₄符合六方相磷酸铈, 纳米粒子长轴尺寸约为20 nm, Ni和Ru均匀分布于纳米CePO₄中; 样品的BET表面积高达178.4 m²/g, ζ电势为-18.2 mV. 以3,3',5,5'-四甲基联苯胺(TMB)作为电子供体和显色剂, 通过分光光度法监测652 nm处的吸光度值对产物浓度进行分析, 结果表明, NiRu-CePO₄催化剂在宽泛的pH范围内表现出类过氧化物酶和类氧化酶活性. 对催化后的催化剂进行表征, 发现样品形貌、 元素分散性和表面Ce的价态均未显著变化, 表明NiRu-CePO₄具有较高的稳定性.     

Peroxidase activity-structure relationship of the intermolecular four-stranded G-quadruplex-hemin complexes and their application in Hg ion detection

The peroxidase activities of the complexes of hemin and intermolecular four-stranded G-quadruplexes formed by short-stranded X_nG_mX_p sequences (X = A, T or C), especially T_nG_mT_p sequences, were compared. The results, combining with those of circular dichroism (CD) spectra and acid-base transition study for DNA-hemin complexes, provide some important information about DNAzymes based on G-quadruplex-hemin complexes, such as the formation of a G-quadruplex structure is an important factor for determining whether a DNA sequence can enhance the catalytic activity of hemin; both intramolecular parallel G-quadruplexes and intermolecular four-stranded parallel G-quadruplexes can enhance the catalytic activity of hemin; the addition of T nucleotides to the 5′-end of a G-tract confers corresponding G-quadruplex greatly enhanced catalytic activity, whereas the addition of T nucleotides to the 3′-end of the G-tract has little effect; the high catalytic activity of hemin in the presence of some short-stranded G-rich sequences may be a result of the reduction of the acidity of the bound hemin cofactor. These studies provide more information for the DNA-hemin peroxidase model system, may help to elucidate the structure-function relationship of peroxidase enzymes and to develop novel, highly efficient peroxidase-liking DNAzymes. As a sequence of such an investigation, a new Hg²⁺ detection method was developed.     

采用可见/近红外光谱检测大麦叶片过氧化氢酶与过氧化物酶含量的研究

采用可见/近红外光谱对丙酯草醚胁迫下大麦叶片过氧化氢酶(catalase,CAT)与过氧化物酶(peroxidase,POD)含量预测进行研究。对500~900nm光谱采用移动平均法(moving average,MA)11点平滑方法进行预处理。采用蒙特卡罗-偏最小二乘法(monte carlo-partial least squares,MCPLS)方法分别对于CAT与POD的含量预测剔除7个与8个异常样本。基于全部光谱建立了CAT与POD含量预测的PLS,最小二乘支持向量机(least-squares support vector machine,LS-SVM)与极限学习机(extreme learning machine,ELM)模型,ELM模型对CAT含量预测效果最好,建模集相关系数(correlation coefficient of calibration,Rc)为0.916,预测集相关系数Rp为0.786;PLS模型对POD含量预测效果最佳,Rc为0.984,Rp为0.876。采用连续投影算法(successive projections algorithm,SPA)算法分别为CAT与POD预测选择了8个与19个特征波长,基于特征波长建立的PLS,LS-SVM与ELM模型中,ELM模型对CAT与POD含量预测效果均最佳,CAT含量预测的相关系数为Rc=0.928,Rp=0.790;POD含量预测的相关系数Rc=0.965,Rp=0.941。基于全谱与基于特征波长的回归分析模型预测效果相当,且对POD含量的预测效果优于对CAT含量的预测效果,而这需要进一步研究以得到精度和稳定性更高的预测模型。研究结果表明,采用可见/近红外光谱结合化学计量学方法可以实现对除草剂胁迫下大麦叶片CAT与POD含量的预测。