Immobilization of hemoglobin on SBA-15 applied to the electrocatalytic reduction of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The direct electron transfer between hemoglobin (Hb) and an electrode was realized by first immobilizing the protein onto SBA-15.The results of the immobilization showed that the adsorption was pH-dependent with a maximum adsorption near the isoelectric point of the protein, and SBA-15 with a larger pore diameter showed greater adsorption capacity for Hb. UV–vis spectroscopy and nitrogen adsorption analysis indicated that Hb was adsorbed within the channel of SBA-15 and no significant denaturation occurred to the protein. The Hb/SBA-15 composite obtained was used for the fabrication of a Hb biosensor to detect hydrogen peroxide. A pair of well-defined redox peaks at −0.337 and −0.370 V on the Hb/SBA-15 composite modified glassy carbon electrode was observed, and the electrode reactions showed a surface-controlled process with a single proton transfer at a scan rate range from 20 to 1,000 mV/s. The sensor showed a fast amperometric response, a low detection limit (2.3 × 10⁻⁹ M) and good stability for the detection of H₂O₂. The electrochemical results indicated that the immobilized Hb still retained its biological activity.     

A photodimerization approach to crosslink and functionalize microgels

Microgels were prepared within reverse micelles via photocrosslinking. Gelation resulted from the [2 + 2] photodimerization reaction of nitrocinnamoyl (NC) groups on multi-arm polyethylene glycol (PEG) or gelatin. Because of the potential for biomedical and chemical applications, immobilization capacity within the microgels was investigated. Quantum dots (QDs), for example, share a similar size scale with proteins and can be physically trapped within the microgels. In addition, the optoelectronic properties of QDs could be utilized for analytical, imaging, and therapeutic purposes. Small molecules and recognition sequences (e.g. biotin) can also be covalently immobilized within the microgel networks through the photodimerization reaction. In the presence of biotin-PEG-NC, the resulting microgels added to streptavidin-coated plates. The microgel properties such as biodegradability and degree of swelling may be engineered for particular applications including targeted monitoring and controlled drug delivery systems.     

Synthesis of Immobilized CMP-Sialic Acids and Their Enzymatic Transfer with Sialyltransferase

A novel immobilization procedure for glycoproteins is based on the reacion of immobilized CMP-NeuAc (CMP-sialic acids) with sialyltransferase (see scheme). The transfer ability was tested under various conditions; a corresponding oligosaccharide or asialoglycoprotein acted as sialyl acceptor. The solid-phase synthesis of CMP-NeuAc is also described.     

Facile Route to Enzyme Immobilization: Gloucose Oxidase Entrapped in Titania Under Mild Environmental Conditions and Consequent Electrochemical Sensor Response

A facile one-step method to the immobilization of the combination of glucose oxidase(GOD) and catalase(CAT) in mesostructured TiO₂ was proposed. The results obtained by transmission electron microspectroscopy and nitrogen adsorption-desorption analysis clearly show that the TiO₂ mediated by the combination of GOD and CAT(CGC) has a large surface area and a narrow pore-size distribution. The CGC immobilized on mesostructured TiO₂ exhibits direct electrochemistry and good electrocatalytic performance without any electron mediator.     

用于农药残留检测的酶生物传感器

酶生物传感器在农药残留检测方面具有传统检测方法不可比拟的优势.本文介绍了胆碱酯酶和有机磷水解酶在生物传感器中的应用,重点介绍了用于有机磷等农药残留分析的酶生物传感器的种类和研究现状,讨论了几种酶固定化方法存在的优势和局限,指出了目前研究需解决的问题并展望了未来的发展方向.     

基于纳米自组装技术的功能化溶胶-凝胶过氧化氢生物传感器

结合功能化溶胶-凝胶(sol-gel)网络结构、自组装技术和纳米粒子效应,提出一种生物传感界面构建方法.利用自组装技术在玻碳电极表面组装氨基化sol-gel膜,通过与自组装膜间的强烈作用将纳米金粒子固定于sol-gel网络中,再通过静电吸附作用实现辣根过氧化物酶(HRP)在纳米金粒子表面的固定化,构建纳米自组装HRP传感界面.将制备的传感器用于对H2O2的催化还原,很好地保持了酶的生物活性,改善了传感器的灵敏度.     

Fabrication of mesoporous SiO2–C–Fe3O4/γ–Fe2O3 and SiO2–C–Fe magnetic composites

A synthetic method for the fabrication of silica-based mesoporous magnetic (Fe or iron oxide spinel) nanocomposites with enhanced adsorption and magnetic capabilities is presented. The successful in situ synthesis of magnetic nanoparticles is a consequence of the incorporation of a small amount of carbon into the pores of the silica, this step being essential for the generation of relatively large iron oxide magnetic nanocrystals (10 ± 3 nm) and for the formation of iron nanoparticles. These composites combine good magnetic properties (superparamagnetic behaviour in the case of SiO₂–C–Fe₃O₄/γ–Fe₂O₃ samples) with a large and accessible porosity made up of wide mesopores (>9 nm). In the present work, we have demonstrated the usefulness of this kind of composite for the adsorption of a globular protein (hemoglobin). The results obtained show that a significant amount of hemoglobin can be immobilized within the pores of these materials (up to 180 mg g⁻¹ for some of the samples). Moreover, we have proved that the composite loaded with hemoglobin can be easily manipulated by means of an external magnetic field.     

Real Time Electrochemical Monitoring of DNA/PNA Dissociation by Melting Curve Analysis

An immobilization‐free electrochemical method is reported for real‐time monitoring of the DNA hybrid dissociation between a ferrocene labeled peptide nucleic acid (PNA) and a fully‐complementary or single‐base‐mismatched DNA. This method takes advantages of electrostatic charge characteristics and interactions among the neutrally charged PNA, the negatively charged DNA and the negatively charged electrode surface made of indium tin oxide (ITO). When a ferrocene labeled PNA (Fc‐PNA) sequence is hybridized to a complementary DNA strand, electrostatic repulsion between the negatively charged PNA/DNA hybrid and the negative ITO surface retards the diffusion of the electroactive Fc to the electrode, resulting in a much reduced electrochemical signal. On the other hand, when the Fc‐PNA is dissociated from the hybrid at elevated temperatures, the neutrally charged Fc‐PNA easily diffuses to the electrode with an enhanced electrochemical signal. Therefore, an electrochemical melting curve of the Fc‐PNA/DNA hybrid can be obtained by measuring the Fc signal with the increasing temperature. This strategy allows monitoring of the dissociation of the DNA hybrid in real time, which might lead to a simple detection method for single nucleotide polymorphism (SNP) analysis.     

Enzyme-functionalized mesoporous silica for bioanalytical applications

The unique properties of mesoporous silica materials (MPs) have attracted substantial interest for use as enzyme-immobilization matrices. These features include high surface area, chemical, thermal, and mechanical stability, highly uniform pore distribution and tunable pore size, high adsorption capacity, and an ordered porous network for free diffusion of substrates and reaction products. Research demonstrated that enzymes encapsulated or entrapped in MPs retain their biocatalytic activity and are more stable than enzymes in solution. This review discusses recent advances in the study and use of mesoporous silica for enzyme immobilization and application in biosensor technology. Different types of MPs, their morphological and structural characteristics, and strategies used for their functionalization with enzymes are discussed. Finally, prospective and potential benefits of these materials for bioanalytical applications and biosensor technology are also presented. Figure Enzyme-functionalized mesoporous silica fibers and their integration in a biosensor design. The immobilization process takes place essentially in the silica micropores.     

Removal of phosphate from aqueous solution by zeolite synthesized from fly ash

Fifteen Chinese fly ashes were converted hydrothermally into zeolites, and phosphate immobilization capacity (PIC) of the synthesized zeolites and the corresponding raw fly ashes were determined using an initial phosphate concentration of 1000 mg/L. Results showed that there was a remarkable increase in PIC (from 1.2 to 7.6 times) following the synthesis process. Fractionation of immobilized phosphorus indicated that Fe+Al-P increased most significantly and consistently among all the phosphorus fractions following the conversion of fly ash to zeolite. The PIC and Ca+Mg-P were closely related to Ca content (with r values of 0.9683 and 0.9651, respectively) rather than Mg content (with r values of 0.3920 and 0.3212, respectively). The r values of PIC and Fe+Al-P with Fe content (with r values of 0.4686 and 0.6385, respectively) were higher than those with Al content (with r values of -0.7857 and -0.3770, respectively). Although calcium and iron components were mainly involved in phosphate immobilization, there was no significant change of Ca and Fe content following the conversion of fly ash to zeolite. Increase in dissociated Fe(2)O(3) and specific surface area probably accounted for the enhancement in PIC of synthesized zeolites compared with corresponding fly ashes. The PIC value of zeolites showed a significant correlation with dissociated Fe(2)O(3) (r=0.6186). The specific surface area increased 26.0-89.4 times as a result of the conversion of fly ash to zeolite. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high, medium and low calcium fly ashes and this behavior was explained by the reaction of phosphate with calcium and iron components.