Ming Zhou

Bioelectrochemical Interface Engineering: Toward the Fabrication of Electrochemical Biosensors, Biofuel Cells, and Self-Powered Logic Biosensors

Over the past decade, researchers have devoted considerable attention to the integration of living organisms with electronic elements to yield bioelectronic devices. Not only is the integration of DNA, enzymes, or whole cells with electronics of scientific interest, but it has many versatile potential applications. Researchers are using these ideas to fabricate biosensors for analytical applications and to assemble biofuel cells (BFCs) and biomolecule-based devices. Other research efforts include the development of biocomputing systems for information processing. In this Account, we focus on our recent progress in engineering at the bioelectrochemical interface (BECI) for the rational design and construction of important bioelectronic devices, ranging from electrochemical (EC-) biosensors to BFCs, and self-powered logic biosensors. Hydrogels and sol-gels provide attractive materials for the immobilization of enzymes because they make EC-enzyme biosensors stable and even functional in extreme environments. We use a layer-by-layer (LBL) self-assembly technique to fabricate multicomponent thin films on the BECI at the nanometer scale. Additionally, we demonstrate how carbon nanomaterials have paved the way for new and improved EC-enzyme biosensors. In addition to the widely reported BECI-based electrochemical impedance spectroscopy (EIS)-type aptasensors, we integrate the LBL technique with our previously developed solid-state probe technique for redox probes immobilization on electrode surfaces to design and fabricate BECI-based differential pulse voltammetry (DPV)-type aptasensors. BFCs can directly harvest energy from ambient biofuels as green energy sources, which could lead to their application as simple, flexible, and portable power sources. Porous materials provide favorable microenvironments for enzyme immobilization, which can enhance BFC power output. Furthermore, by introducing aptamer-based logic systems to BFCs, such systems could be applied as self-powered and intelligent aptasensors for the logic detection. We have developed biocomputing keypad lock security systems which can be also used for intelligent medical diagnostics. BECI engineering provides a simple but effective approach toward the design and fabrication of EC-biosensors, BFCs, and self-powered logic biosensors, which will make essential contributions in the development of creative and practical bioelectronic devices. The exploration of novel interface engineering applications and the creation of new fabrication concepts or methods merit further attention.

Highly ordered mesoporous carbons as electrode material for the construction of electrochemical dehydrogenase- and oxidase-based biosensors

In this work, the excellent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors. The high density of edge-plane-like defective sites and high specific surface area of OMCs could be responsible for the electrocatalytic behavior at OMCs modified glassy carbon electrode (OMCs/GE), which induced a substantial decrease in the overpotential of NADH and H(2)O(2) oxidation reaction compared to carbon nanotubes modified glassy carbon electrode (CNTs/GE). Such ability of OMCs permits effective low-potential amperometric biosensing of ethanol and glucose, respectively, at Nafion/ADH-OMCs/GE and Nafion/GOD-OMCs/GE. Especially, as an amperometric glucose biosensor, Nafion/GOD-OMCs/GE showed large determination range (500-15,000 micromoll(-1)), high sensitivity (0.053 nA micromol(-1)), fast (9+/-1s) and stable response (amperometric response retained 90% of the initial activity after 10h stirring of 2 mmoll(-1) glucose solution) to glucose as well as the effective discrimination to the possible interferences, which may make it to readily satisfy the need for the routine clinical diagnosis of diabetes. By comparing the electrochemical performance of OMCs with that of CNTs as electrode material for the construction of ADH- and GOD-biosensors in this work, we reveal that OMCs could be a favorable and promising carbon electrode material for constructing other electrochemical dehydrogenase- and oxidase-based biosensors, which may have wide potential applications in biocatalysis, bioelectronics and biofuel cells.

Graphene Enhanced Electron Transfer at Aptamer Modified Electrode and Its Application in Biosensing

Graphene (GN), a two-dimensional and one-atom thick carbon sheet, is showing exciting applications because of its unique morphology and properties. In this work, a new electrochemical biosensing platform by taking advantage of the ultrahigh electron transfer ability of GN and its unique GN/ssDNA interaction was reported. Adenosine triphosphate binding aptamer (ABA) immobilized on Au electrode could strongly adsorb GN due to the strong π-π interaction and resulted in a large decrease of the charge transfer resistance (R(ct)) of the electrode. However, the binding reaction between ABA and its target adenosine triphosphate (ATP) inhibited the adsorption of GN, and R(ct) could not be decreased. On the basis of this, we developed a new GN-based biosensing platform for the detection of small molecule ATP. The experimental results confirmed that the electrochemical aptasensor we developed possessed a good sensitivity and high selectivity for ATP. The detection range for ATP was from 15 × 10(-9) to 4 × 10(-3) M. The method here was label-free and sensitive and did not require sophisticated fabrication. Furthermore, we can generalize this strategy to detect Hg(2+) using a thymine (T)-rich, mercury-specific oligonucleotide. Therefore, we expected that this method may offer a promising approach for designing high-performance electrochemical aptasensors for the sensitive and selective detection of a spectrum of targets.

Au NPs-enhanced surface plasmon resonance for sensitive detection of mercury(II) ions.

We reported a sensitive surface plasmon resonance (SPR) sensor for the detection of Hg(2+) in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe was first immobilized on gold film through formation of Au-S bond between DNA and gold film. In the presence of Hg(2+), the MSO probe captured free Hg(2+) in aqueous media via the Hg(2+)-mediated coordination of T-Hg(2+)-T base pairs. This direct immobilization strategy led to a detection limit of 0.3 microM of Hg(2+). In order to improve the sensitivity, part complementary DNA (PCS)-modified Au NPs labels were employed to amplify SPR signals. We demonstrated that this Au NPs-based sensing strategy resulted in a detection limit down to 5 nM of Hg(2+), brings about an amplification factor of two orders of magnitude. This Au NPs-based Hg(2+) sensor also exhibited excellent selectivity over a spectrum of interference metal ions. Taking advantage of the high amplifying characteristic of Au NPs and the specificity of MSO to Hg(2+) recognition, we developed here a SPR sensor for specific Hg(2+) detection with high sensitivity.

Microfluidic Electrochemical Aptameric Assay Integrated On-Chip: A Potentially Convenient Sensing Platform for the Amplified and Multiplex Analysis of Small Molecules

Aptamers are artificial oligonucleotides that have been widely employed to design biosensors (i.e., aptasensors). In this work, we report a microfluidic electrochemical aptamer-based sensor (MECAS) by constructing Au-Ag dual-metal array three-electrode on-chip for multiplex detection of small molecules. In combination with the microfluidic channels covering on the glass chip, different targets are transported to the Au electrodes integrated on different positions of the chip. These electrodes are premodified by different kinds of aptamers, respectively, to fabricate different sensing interfaces which can selectively capture the corresponding target. It is an address-dependent sensing platform; thus, with the use of only one electrochemical probe, multitargets can be recognized and detected according to the readout on a corresponding aptamer-modified electrode. In the sensing strategy, the electrochemical probe, [Ru(NH(3))(6)](3+) (RuHex), which can quantitatively bind to surface-confined DNA via electrostatic interaction, was used to produce chronocoulometric signal; Au nanoparticles (AuNPs) were used to improve the sensitivity of the sensor by amplifying the detection signals. Moreover, the sensing interface fabrication, sample incubation, and electrochemical detection were all performed in microfluidic channels. By using this detection chip, we achieved the multianalysis of two model small molecules, ATP, and cocaine, in mixed samples within 40 min. The detection limit of ATP was 3 × 10(-10) M, whereas the detection limit of cocaine was 7 × 10(-8) M. This Au-Ag dual metal electrochemical chip detector integrated MECAS was simple, sensitive, and selective. Also it is similar to a dosimeter which accumulates signal upon exposure. It held promising potential for designing electrochemical devices with high throughput, high automation, and high integration in multianalysis.

A novel homogeneous label-free aptasensor for 2,4,6-trinitrotoluene detection based on an assembly strategy of electrochemiluminescent graphene oxide with gold nanoparticles and aptamer

We report a novel homogeneous label-free aptasensor for 2,4,6-trinitrotoluene (TNT) detection based on an assembly strategy of electrochemiluminescent graphene oxide (GO) with gold nanoparticles (AuNPs) and aptamer. In this sensing strategy, the anti-TNT aptamer was first assembled with AuNPs to form aptamer-AuNPs. Then ruthenium(II) complex functionalized GO (denoted as Ru-GO) was assembled with aptamer-AuNPs by electrostatic interaction. AuNPs could directly quench the electrochemiluminescence (ECL) emission of ruthenium(II) complex on the surface of Ru-GO due to the energy transfer from luminophore to the AuNPs. Weak ECL signal of the assembly was obtained. In the presence of target molecule TNT, the aptamer-AuNPs would aggregate partly due to the aptamer-target interaction and reduce quenching effect, leading to ECL signal restoration and strong ECL signal was obtained. TNT in a range of 0.01-100ngmL(-1) could be detected by use of the ECL intensity discrepancy with a low detection limit of 3.6pgmL(-1). The aptasensor also showed high selectivity towards TNT against 2,4-dinitrotoluene, p-nitrotoluene and nitrobenzene. The present aptasensor has been successfully applied to the detection of TNT in real water samples. Compared with previous reported sensors, this homogenous aptasensor avoided complicated labeling and purification procedure and showed magnificent sensitivity and high selectivity, which made it not only convenient but also time-saving and applicable. Furthermore, this sensing strategy also provides a promising way to develop new ECL aptasensor for other analytes by virtue of other aptamers.

A homogeneous signal-on strategy for the detection of rpoB genes of Mycobacterium tuberculosis based on electrochemiluminescent graphene oxide and ferrocene quenching.

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality all over the world and multidrug resistance TB (MDR-TB) pose a serious threat to the TB control and represent an increasing public health problem. In this work, we report a homogeneous signal-on electrochemiluminescence (ECL) DNA sensor for the sensitive and specific detection of rpoB genes of MDR-TB by using ruthenium(II) complex functionalized graphene oxide (Ru-GO) as suspension sensing interface and ferrocene-labeled ssDNA (Fc-ssDNA) as ECL intensity controller. The ECL of Ru-GO could be effectively quenched by Fc-ssDNA absorbed on the Ru-GO nanosheets. The Ru-GO has good discrimination ability over ssDNA and dsDNA. Mutant ssDNA target responsible for the drug resistant tuberculosis can hybridize with Fc-ssDNA and release Fc-ssDNA from Ru-GO surface, leading to the recovery of ECL. Mutant ssDNA target can be detected in a range from 0.1 to 100 nM with a detection limit of 0.04 nM. The proposed protocol is sensitive, specific, simple, time-saving and polymerase chain reaction free without complicated immobilization, separation and washing steps, which creates a simple but valuable tool for facilitating fast and accurate detection of disease related specific sequences or gene mutations.

A biofuel cell with a single-walled carbon nanohorn-based bioanode operating at physiological condition

Single-walled carbon nanohorns (SWNHs), a new type of carbon nanomaterials, possess excellent catalytic properties, high-purity, and low toxicities, which make them suitable for bioelectrochemical application. Here a biofuel cell anode has been developed by using SWNHs as the support for redox mediator and biocatalyst for the first time. Cyclic voltammetric results show SWNHs promotes the electropolymerization of methylene blue (MB) and the resulted nanocomposite (poly MB-SWNHs) exhibits prominent catalytic ability to the oxidation of nicotinamide adenine dinucleotide. Glucose dehydrogenase was then immobilized on the poly MB-SWNHs modified electrode for the oxidation of glucose. Employing Pt nanoparticles supported on functionalized TiO(2) colloidal spheres with nanoporous surface as cathode catalyst, the as-assembled glucose/O(2) biofuel cell operate at the physiological condition with good performance.

Synthesis and electrochemiluminescence of bis(2,2′-bipyridine)(5-amino-1,10-phenanthroline) ruthenium(II)-functionalized gold nanoparticles

Bis(2,2′-bipyridine)(5-amino-1,10-phenanthroline) ruthenium(II) functionalized gold nanoparticles with electrochemiluminescence activity were successfully synthesized by a simple one-pot method via the reduction of HAuCl4 with NaBH4 in the presence of bis(2,2′-bipyridine)(5-amino-1,10-phenanthroline) ruthenium(II), which is of great potential for application in bioanalysis.