Replacing Mg2+ by Fe2+ for RNA-Cleaving DNAzymes

It has been proposed that Mg²⁺ and Fe²⁺ are very similar in interacting with ribozymes and some protein-based enzymes, but their activities with DNAzymes have yet to be studied. Here, the activity of Fe²⁺ as cofactor for a few RNA-cleaving DNAzymes is investigated. 17E is a well-studied DNAzyme that is active in the presence of many different divalent metal ions; it is highly active with Fe²⁺ with an apparent K_d of 29.7±2.3 μm and a k_obs of 1.12±0.11 min⁻¹ in the presence of 1 mm Fe²⁺ at pH 7.5. Fe²⁺ has 21-fold higher activity than Mg²⁺. Six different DNAzymes are then tested, and only the DNAzymes active with Mg²⁺ (17E, 8–17, and E5) are active with Fe²⁺. Fe²⁺ has 25 and one- to twofold higher activity than Mg²⁺ for the 8–17 and E5 DNAzymes, respectively. In pH>7 buffer and in presence of air, 1 mm Fe²⁺ results in a nonspecific degradation of the DNA strand due to reactive oxygen species (ROS). Cleavage reactions in anoxic environment and antioxidant ascorbate can be used to overcome the effect of oxidation. The findings provide insights for potential DNAzyme catalysis in the early Earth, and they further support the similarity between Mg²⁺ and Fe²⁺ in enzyme catalysis.     

Non‐Toxic Dry‐Coated Nanosilver for Plasmonic Biosensors

The plasmonic properties of noble metals facilitate their use for in vivo bio‐applications such as targeted drug delivery and cancer cell therapy. Nanosilver is best suited for such applications as it has the lowest plasmonic losses among all such materials in the UV‐visible spectrum. Its toxicity, however, can destroy surrounding healthy tissues and thus, hinders its safe use. Here, that toxicity against a model biological system (Escherichia coli) is “cured” or blocked by coating nanosilver hermetically with a about 2 nm thin SiO₂ layer in one‐step by a scalable flame aerosol method followed by swirl injection of a silica precursor vapor (hexamethyldisiloxane) without reducing the plasmonic performance of the enclosed or encapsulated silver nanoparticles (20–40 nm in diameter as determined by X‐ray diffraction and microscopy). This creates the opportunity to safely use powerful nanosilver for intracellular bio‐applications. The label‐free biosensing and surface bio‐functionalization of these ready‐to‐use, non‐toxic (benign) Ag nanoparticles is presented by measuring the adsorption of bovine serum albumin (BSA) in a model sensing experiment. Furthermore, the silica coating around nanosilver prevents its agglomeration or flocculation (as determined by thermal annealing, optical absorption spectroscopy and microscopy) and thus, enhances its biosensitivity, including bioimaging as determined by dark field illumination.     

Chirality‐Based Biosensors

The fabrication of chiral nanostructures gives rise to characteristic chiroptical activity, which can be used for chirality‐based biosensors. Great progress is made in the use of nanoassemblies for the construction of chiral nanoparticle dimers, pyramids, helices, and twisted structures, and their chiroptical activities correlate with diverse structural geometries and enantiomeric configurations. In DNA‐hybridization‐based chiral nanoassemblies, the assembly parameters, such as the components, gaps, multicomponents, and the aftergrowth of metal, can result in multiple bands and enhanced chiroptical effects. Based on known chiral nanostructures, the existing chiral nanoassembly‐based biosensors together with their targets and signal amplification strategies are reviewed. Chirality involves multiple signals, and multitarget biosensors are introduced with newly developed chiral architectures for the accurate and reliable monitoring of biomarkers in living cells. The interactions between chiral nanoarchitectures and biosystems are also highlighted, which are important not only in the chiral dynamic switching of nano‐objects for biomonitoring, but also in manipulating cell growth, proliferation, and adhesion. The future perspectives on chiral fabrication and its use in biosensors are also comprehensively discussed.     

Advances in Bioapplications of Carbon Nanotubes

This progress report provides an overview on recent advances in bioapplications of carbon nanotubes including the chemical modification of carbon nanotubes, targeting specifically their covalent and noncovalent conjugations with a variety of biological and bioactive species (proteins and peptides, DNAs/RNAs, and carbohydrates). Furthermore, the significant recent development and progress in the use of carbon nanotubes for biosensors, drug and other delivery systems, bioimaging, etc. and in the understanding of in vivo biodistribution and toxicity of carbon nanotubes are reported.     

Tailored Graphitic Carbon Nitride Nanostructures: Synthesis,Modification, and Sensing Applications

Various beneficial properties of graphitic carbon nitride (g‐CN) have been discovered during the promotion of its visible‐light‐driven photocatalytic activity for water splitting. These properties enable g‐CN working as a sensing signal transducer with multiple output modes. In this review, state‐of‐the‐art sensing applications of tailored g‐CN nanostructures in the recent years are presented. Initially, g‐CN nanoarchitectures featuring large surface areas, abundance of active sites, and high dispersity in water are presented along with their preparation methods. Then, sensing applications of these g‐CN nanoarchitectures are described in sequence of the immobilization of recognition elements; semiconductor and electron donating properties derive signaling transduction modes, and efficient approaches for improving sensing performances. The review is concluded with a summary and some perspectives on the challenges and future possibilities of this research field.     

Enzymatic sensing with laccase-functionalized textile organic biosensors

Herein we present a textile wearable electrochemical transistor by functionalizing a single cotton yarn with semiconducting polymer. The organic electrochemical transistor (OECT), which is low cost and completely integrated e-textile, is decorated by adsorption of the fungal laccase POXA1b, and is used as biosensor for the direct detection of Tyrosine (L-Tyr) without the use of electron mediators. The detection of Tyr in real-case scenario such as human physiological fluids would own a paramount importance in noninvasive analysis of the patient's condition, monitoring and preventing several pathologies. To assess the reaction progression, the redox process is studied by UV–visible absorption with test reference molecule of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS): the results confirmed that the oxidation reaction is driven by the presence of laccase enzyme and direct electron transfer occurred. The modulation of the signal response and the kinetic of the signal is used to detect Tyr molecule in aqueous solution and the role of the enzyme adsorption on the textile is analyzed. A kinetic analysis of the characteristic modulation times of the sensing curves, confirm the sensing properties of the textile device. The textile-based biosensor is demonstrated to monitor human health biomarkers through wearable applications in a non-invasive way, finding potential application in sport, healthcare and working safety.     

Optimal modification of annexin V with fluorescent dyes

The many uses of chemically modified annexin Vs necessitate an understanding of the optimal degree of modification and modification sites of the protein. When reacted with the N-hydroxysuccinimide ester of Cy5.5, annexin V with one modification per mole of protein retained its affinity for phosphatidylserine of apoptotic cells, whereas modification with two dyes per mole of protein caused a complete loss of activity. A tryptic digest LC/MS method was used to identify the modification sites as either of two closely spaced lysine residues, in position 286 or 290. The crystal structure indicated the location of these lysines was distal to the phosphatidylserine binding sites on annexin V. These results can be used to develop active or inactive fluorescent control annexin V proteins and to suggest strategies for attaining higher levels of modification with retention of bioactivity.     

Two-dimensional multiarray formation of hepatocyte spheroids on a microfabricated PEG-brush surface

A two-dimensional microarray of ten thousand (100 x 100) hepatocyte heterospheroids, underlaid with endothelial cells, was successfully constructed with 100 microm spacing in an active area of 20 x 20 mm on microfabricated glass substrates that were coated with poly(ethylene glycol) brushes. Cocultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100 microm, functioning as a miniaturized liver to secret albumin for at least one month. The most important feature of this study is that these substrates are defined to provide an unprecedented control of substrate properties for modulating cell behavior, employing both surface engineering and synthetic polymer chemistry. The spheroid array constructed here is highly useful as a platform of tissue and cell-based biosensors and detects a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.     

生物传感器的研究现状和发展趋势

生物传感器是发展生物技术必不可少的一种先进的检测与监控元件,具有广阔的发展前景,是传感器的一个重要研究方面.本文综述了生物传感器的结构特点、基本原理以及研究现状,探讨了生物传感器的发展趋势.