Bifunctional Trehalose Anode Incorporating Two Covalently Linked Enzymes Acting in Series

Energy consumption during insect flight and bioinspiration for MAV design: A review

The excellent biological characteristics of insects provide an important source of inspiration for designing micro air vehicles (MAVs). Insect flight is an incredibly complex and energy-intensive process. Unique insect flight muscles and contraction mechanisms enable flapping at high frequencies. Moreover, the metabolic rate during flight can reach hundreds of times the resting state. Understanding energy consumption during flight is crucial for designing efficient biomimetic aircraft. This paper summarizes the structures and contraction mechanisms of insect flight muscles, explores the underlying metabolic processes, and identifies methods for energy substrate identification and detection, and discusses inspiration for biomimetic MAV design. This paper reviews energy consumption during insect flight, promotes the understanding of insect bioenergetics, and applies this information to the design of MAVs.

Sensitive Fluorescent Sensor for Recognition of HIV-1 dsDNA by Using Glucose Oxidase and Triplex DNA

A sensitive fluorescent sensor for sequence-specific recognition of double-stranded DNA (dsDNA) was developed on the surface of silver-coated glass slide (SCGS). Oligonucleotide-1 (Oligo-1) was designed to assemble on the surface of SCGS and act as capture DNA, and oligonucleotide-2 (Oligo-2) was designed as signal DNA. Upon addition of target HIV-1 dsDNA (Oligo-3•Oligo-4), signal DNA could bind on the surface of silver-coated glass because of the formation of C•GoC in parallel triplex DNA structure. Biotin-labeled glucose oxidase (biotin-GOx) could bind to signal DNA through the specific interaction of biotin-streptavidin, thereby GOx was attached to the surface of SCGS, which was dependent on the concentration of target HIV-1 dsDNA. GOx could catalyze the oxidation of glucose and yield H₂O₂, and the HPPA can be oxidized into a fluorescent product in the presence of HRP. Therefore, the concentration of target HIV-1 dsDNA could be estimated with fluorescence intensity. Under the optimum conditions, the fluorescence intensity was proportional to the concentration of target HIV-1 dsDNA over the range of 10 pM to 1000 pM, the detection limit was 3 pM. Moreover, the sensor had good sequence selectivity and practicability and might be applied for the diagnosis of HIV disease in the future.

Contribution of convection and diffusion to the cascade reaction kinetics of β-galactosidase/glucose oxidase confined in a microchannel

The spatial positioning of enzymes and mass transport play crucial roles in the functionality and efficiency of enzyme cascade reactions. To fully understand the mass transport regulating kinetics of enzyme cascade reactions, we investigated the contribution of convective and diffusive transports to a cascade reaction of β-galactosidase (β-Gal)/glucose oxidase (GOx) confined in a microchannel. β-Gal and GOx are assembled on two separated gold films patterned in a polydimethylsiloxane (PDMS) microchannel with a controllable distance from 50 to 100 μm. Experimental results demonstrated that the reaction yield increases with decreasing distance between two enzymes and increasing substrate flow rate. Together with the simulation results, we extracted individual reaction kinetics of the enzyme cascade reaction and found that the reaction rate catalyzed by β-Gal occurred much faster than by GOx, and thus, the β-Gal catalytic reaction showed diffusion controll, whereas the GOx catalytic reaction showed kinetic controll. Since the decrease in the enzymes distance shortens the transport length of intermediate glucose to GOx, the amount of glucose reaching GOx will be increased in the unit time, and in turn, the enzyme cascade reaction yield will be increased with decreasing the gap distance. This phenomenon is similar to the intermediates pool of tricarboxylic acid (TCA) cycle in the metabolic system. This study promotes the understanding of the metabolic/signal transduction processes and active transport in biological systems and promises to design high performance biosensors and biofuel cells systems.

Enzyme Immobilization and Mediation with Osmium Redox Polymers

Enzymatic electrodes are becoming increasingly common for energy production and sensing applications. Research over the past several decades has addressed a major issue that can occur when using these biocatalysts, i.e., slow heterogeneous electron transfer, by incorporation of a redox active species to act as an electron shuttle. There are several advantages to immobilizing both the enzyme and mediator at the enzyme surface, including increased electron transfer rates, decreased enzyme leaching, and minimized diffusion limitations. Redox polymers consisting of a redox active center attached to a polymer backbone are a particularly attractive option because they have high self-exchange rates for electron transfer and tunable redox potential. Osmium (Os) polymers are the most well studied of this type of polymer for bioelectrocatalysis. Here, we describe the methods to synthesize one of the most common Os redox polymers and how it can be used to fabricate glucose oxidase electrodes. Procedures are also outlined for evaluating the enzymatic electrodes.

Sortase A-catalyzed site-specific coimmobilization on microparticles via streptavidin

A microparticle surface was designed by the unique method incorporating streptavidin-biotin affinity and sortase A (SrtA)-catalyzed transpeptidation. Leucine-proline-glutamate-threonine-glycine-tagged streptavidin (Stav-LPETG)was immobilized on the surface using streptavidin-biotin affinity, and GGGGG-tagged red fluorescent protein (Gly5-RFP) was conjugated with SrtA. Biotinylated fluorescein isothiocyanate (biotin-FITC) was then bound to residual biotin-binding sites in Stav-LPETG. The resulting particles had RFP and FITC immobilized on the surface via Stav-LPETG, and RFP- and FITC-associated fluorescence was observed using fluorescence microscopy. Finally, GGG-tagged glucose oxidase and biotinylated horseradish peroxidase were immobilized on the microparticle surface, resulting in a functional particle capable of detecting glucose. This particle can be repeatedly used and is more sensitive in detecting glucose than particles prepared using chemical modification. Our method provides a simple strategy for site-specific coimmobilization on molecular surfaces and expands the use of protein hybrid devices.