用单壁纳米碳管制备葡萄糖生物传感器的研究

以单壁纳米碳管为代表材料,对利用纳米碳管制备葡萄糖生物传感器中纳米碳管的作用和纳米碳管修饰电极的方法、酶的固定化方法及电极种类等因素对传感器性能的影响进行了研究.研究结果表明,纳米碳管的加入能有效地改善传感器的电化学性能,利用二茂铁和单壁纳米碳管共同修饰电极所制得的传感器的性能要好于仅用单壁纳米碳管修饰电极制得的传感器.在酶的固定化方法中,戊二醛交联法要略好于明胶包埋法;而利用铂电极制备出的生物传感器对葡萄糖的响应电流要明显高于利用金电极和玻碳电极制备出的生物传感器.这些结论对于开发纳米碳管在生物传感领域及生命科学相关领域的应用有参考价值.     

A large-area nanoscale gold hemisphere pattern as a nanoelectrode array

Two-dimensional (2D) nanostructure patterns have extensive applications in photonic devices, nanoelectronics, electrochemical devices, biosensors, catalysts and high-density magnetic recording devices. It remains a challenge to develop low-cost, high-throughput, high-resolution techniques for the fabrication of large-area (wafer-scale) 2D nanostructure array patterns with controlled feature size, shape and pitch. The present work has demonstrated a low-cost, high-throughput, high-resolution approach for the fabrication of large-area, high-quality nanostructure array patterns by nanosphere lithography combined with electroplating. The gold hemisphere array pattern obtained is capable of functioning as a nanoelectrode array (NEA) in which the gold hemispheres act as individual electrodes that are separated with an insulating polypyrrole (PPY) film. Cyclic voltammetry measurement has shown a sigmoid-shaped voltammogram, which is characteristic of electrochemical characteristics of a nanoelectrode array. NEAs are expected to find extensive applications in fundamental electrochemistry studies and electrochemical devices.     

Rational design and one-step formation of multifunctional gel transducer for simple fabrication of integrated electrochemical biosensors

This study demonstrates a new strategy to simplify the biosensor fabrication and thus minimize the biosensor-to-biosensor deviation through rational design and one-step formation of a multifunctional gel electronic transducer integrating all elements necessitated for efficiently transducing the biorecognition events to signal readout, by using glucose dehydrogenase (GDH) based electrochemical biosensor as an example. To meet the requirements for preparing integrated biosensors and retaining electronic and ionic conductivities for electronically transducing process, ionic liquids (ILs) with enzyme cofactor (i.e., oxidized form of nicotinamide adenine dinucleotide) as the anion were synthesized and used to form a bucky gel with single-walled carbon nanotubes, in which methylene green electrocatalyst was stably encapsulated for the oxidation of nicotinamide adenine dinucleotide. With such kind of rationally designed and one-step-formed multifunctional gel as the electronic transducer, the GDH-based electrochemical biosensors were simply fabricated by polishing the electrodes onto the gel followed by enzyme immobilization. This capability greatly simplifies the biosensor fabrication, prolongs the stability of the biosensors, and, more remarkably, minimizes the biosensor-to-biosensor deviation. The relative standard deviations obtained both with one electrode for the repeated measurements of glucose and with the different electrodes prepared with the same method for the concurrent measurements of glucose with the same concentration were 3.30% (n = 7) and 4.70% (n = 6), respectively. These excellent properties of the multifunctional gel-based biosensors substantially enable them to well-satisfy the pressing need of rapid measurements, for example, environmental monitoring, food analysis, and clinical diagnoses.     

Multisegment nanowire sensors for the detection of DNA molecules

We describe a novel application for detecting specific single strand DNA sequences using multisegment nanowires via a straightforward surface functionalization method. Nanowires comprising CdTe-Au-CdTe segments are fabricated using electrochemical deposition, and electrical characterization indicates a p-type behavior for the multisegment nanostructures, in a back-to-back Schottky diode configuration. Such nanostructures modified with thiol-terminated probe DNA fragments could function as high fidelity sensors for biomolecules at very low concentration. The gold segment is utilized for functionalization and binding of single strand DNA (ssDNA) fragments while the CdTe segments at both ends serve to modulate the equilibrium Fermi level of the heterojunction device upon hybridization of the complementary DNA fragments (cDNA) to the ssDNA over the Au segment. Employing such multisegment nanowires could lead to the fabrication more sophisticated and high multispecificity biosensors via selective functionalization of individual segments for biowarfare sensing and medical diagnostics applications.     

A bioconjugated polyglycerol dendrimer with glucose sensing properties

In this work, the biological and electrochemical properties of glucose biosensor based on polyglycerol dendrimer (PGLD) is presented. Streptokinase (SK), glucose oxidase (GOx) and phosphorylcholine (PC) were immobilized onto PGLD to obtain a blood compatible bioconjugate with glucose sensing properties. The bioconjugated PGLD was entrapped in polyaniline nanotubes (PANINT's) through template electrochemical polymerization of aniline. PANINT's were used as electron mediator due to their high ability to promote electron-transfer reactions involving GOx. Platelet adhesion, fibrinolytic activity and protein adsorption were studied by in vitro experiments to examine the interaction of blood with PGLD biosensor. The PGLD biosensor exhibits a strong and stable amperometric response to glucose. The enzyme affinity for the substrate (K (M) (app) ) indicates that the enzyme activity was not significantly altered after the bioconjugation of GOx with PGLD dendrimer. The bioelectrochemical properties suggest that the bioconjugated PGLD developed in this work appears to be a good candidate for providing interfaces for implantable biosensors, especially oxidoreductase-based sensors.     

Electrochemical biosensor based on integrated assembly of dehydrogenase enzymes and gold nanoparticles

Development of a highly sensitive nanostructured electrochemical biosensor based on the integrated assembly of dehydrogenase enzymes and gold (Au) nanoparticle is described. The Au nanoparticles (AuNPs) have been self-assembled on a thiol-terminated, sol-gel-derived, 3-D, silicate network and enlarged by hydroxylamine seeding. The AuNPs on the silicate network efficiently catalyze the oxidation of NADH with a decrease in overpotential of approximately 915 mV in the absence of any redox mediator. The surface oxides of AuNP function as an excellent mediator, and a special inverted "V" shape voltammogram at less positive potential was observed for the oxidation of NADH. The AuNP self-assembled sol-gel network behaves like a nanoelectrode ensemble. The nanostructured electrode shows high sensitivity (0.056 +/- 0.001 nA/nM) toward NADH with an amperometric detection limit of 5 nM. The electrode displays excellent operational and storage stability. A novel methodology for the fabrication of a NADH-dependent dehydrogenase biosensor based on the integration of dehydrogenase enzyme and AuNPs with the silicate network is developed. The enzymatically generated NADH is, in turn, electrocatalytically detected by the AuNPs on the silicate network. The integrated assembly has been successfully used for the amperometric biosensing of lactate and ethanol at a potential of -5 mV. The biosensor is very stable and highly sensitive, and it has a fast response time. The excellent performance validates the integrated assembly as an attractive sensing element for the development of new dehydrogenase biosensors.     

Immobilization of enzymes through one-pot chemical preoxidation and electropolymerization of dithiols in enzyme-containing aqueous suspensions to develop biosensors with improved performance

A protocol of one-pot chemical preoxidation and electropolymerization of monomers (CPEM) in enzyme-containing aqueous suspensions (or solutions) was proposed as a universal strategy for high-activity and high-load immobilization of enzymes to construct amperometric biosensors, which was proven to be effective for the monomer of 1,4-benzenedithiol (BDT), 1,6-hexanedithiol, o-phenylenediamine, o-aminophenol or pyrrole, the preoxidant of K3Fe(CN)6 or p-benzoquinone, and the enzyme of glucose oxidase (GOx) or alkaline phosphatase (AP) to develop GOx-based glucose biosensors or AP-based disodium phenyl phosphate biosensors. As a case examined in detail, a well-dispersed aqueous suspension of the poorly soluble BDT was obtained through its dispersion assisted by ultrasonication and coexisting GOx, which was then subject to chemical preoxidation through adding K3Fe(CN)6, yielding many composites of insoluble BDT oligomers with lots of high-activity enzyme molecules entrapped. Some insoluble composites were then electrochemically codeposited with poly(1,4-benzenedithiol) on an Au electrode, yielding an enzyme film with high-load and high-activity enzyme immobilized. The glucose biosensor prepared here from the CPEM protocol showed much better performance than that from the preoxidant-free conventional electropolymerization (CEP) protocol, with a detection sensitivity increase by a factor of 32 in this case. The GOx-based and AP-based first-generation biosensors developed from the present CPEM protocol all exhibited notably improved performance compared with the analogues from the preoxidant-free CEP protocol. The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate various electrode modification processes. The values of quantity and enzymatic specific activity (ESA) of the immobilized enzymes were evaluated through the EQCM and the conventional UV-vis spectrophotometric method, given that the CPEM protocol notably improved the quantity and the ESA of immobilized enzymes as compared with the preoxidant-free CEP protocol. The proposed CPEM protocol may be interesting in a number of fields, including biosensing, biocatalysis, biofuel cells, bioaffinity chromatography, and biomaterials, and the successful electropolymerization of dithiols in aqueous suspensions (two-phase electropolymerization) may open a new avenue for many monomers that are poorly soluble in neutral aqueous solutions to in situ immobilize biomolecules for bioapplications.     

Large‐Scale Plasmonic Hybrid Framework with Built‐In Nanohole Array as Multifunctional Optical Sensing Platforms

Light coupling with patterned subwavelength hole arrays induces enhanced transmission supported by the strong surface plasmon mode. In this work, a nanostructured plasmonic framework with vertically built‐in nanohole arrays at deep‐subwavelength scale (6 nm) is demonstrated using a two‐step fabrication method. The nanohole arrays are formed first by the growth of a high‐quality two‐phase (i.e., Au–TiN) vertically aligned nanocomposite template, followed by selective wet‐etching of the metal (Au). Such a plasmonic nanohole film owns high epitaxial quality with large surface coverage and the structure can be tailored as either fully etched or half‐way etched nanoholes via careful control of the etching process. The chemically inert and plasmonic TiN plays a role in maintaining sharp hole boundary and preventing lattice distortion. Optical properties such as enhanced transmittance and anisotropic dielectric function in the visible regime are demonstrated. Numerical simulation suggests an extended surface plasmon mode and strong field enhancement at the hole edges. Two demonstrations, including the enhanced and modulated photoluminescence by surface coupling with 2D perovskite nanoplates and the refractive index sensing by infiltrating immersion liquids, suggest the great potential of such plasmonic nanohole array for reusable surface plasmon‐enhanced sensing applications.     

Nondestructive Real‐Time Monitoring of Enhanced Stem Cell Differentiation Using a Graphene‐Au Hybrid Nanoelectrode Array

Stem cells have attracted increasing research interest in the field of regenerative medicine because of their unique ability to differentiate into multiple cell lineages. However, controlling stem cell differentiation efficiently and improving the current destructive characterization methods for monitoring stem cell differentiation are the critical issues. To this end, multifunctional graphene–gold (Au) hybrid nanoelectrode arrays (NEAs) to: (i) investigate the effects of combinatorial physicochemical cues on stem cell differentiation, (ii) enhance stem cell differentiation efficiency through biophysical cues, and (iii) characterize stem cell differentiation in a nondestructive real‐time manner are developed. Through the synergistic effects of physiochemical properties of graphene and biophysical cues from nanoarrays, the graphene‐Au hybrid NEAs facilitate highly enhanced cell adhesion and spreading behaviors. In addition, by varying the dimensions of the graphene‐Au hybrid NEAs, improved stem cell differentiation efficiency, resulting from the increased focal adhesion signal, is shown. Furthermore, graphene‐Au hybrid NEAs are utilized to monitor osteogenic differentiation of stem cells electrochemically in a nondestructive real‐time manner. Collectively, it is believed the unique multifunctional graphene‐Au hybrid NEAs can significantly advance stem‐cell‐based biomedical applications.     

ZnS nanoparticles electrodeposited onto ITO electrode as a platform for fabrication of enzyme-based biosensors of glucose

The electrochemical and photoelectrochemical biosensors based on glucose oxidase (GOD) and ZnS nanoparticles modified indium tin oxide (ITO) electrode were investigated. The ZnS nanoparticles were electrodeposited directly on the surface of ITO electrode. The enzyme was immobilized on ZnS/ITO electrode surface by sol–gel method to fabricate glucose biosensor. GOD could electrocatalyze the reduction of dissolved oxygen, which resulted in a great increase of the reduction peak current. The reduction peak current decreased linearly with the addition of glucose, which could be used for glucose detection. Moreover, ZnS nanoparticles deposited on ITO electrode surface showed good photocurrent response under illumination. A photoelectrochemical biosensor for the detection of glucose was also developed by monitoring the decreases in the cathodic peak photocurrent. The results indicated that ZnS nanoparticles deposited on ITO substrate were a good candidate material for the immobilization of enzyme in glucose biosensor construction.     

GOX-functionalized nanodiamond films for electrochemical biosensor

The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor.     

Sensitive determination of uric acid by using graphene quantum dots as a new substrate for immobilisation of uric oxidase

A novel strategy for highly sensitive electrochemical detection of uric acid (UA) was proposed based on graphene quantum dots (GQDs), GQDs were introduced as a suitable substrate for enzyme immobilisation. Uric oxidase (UOx) was immobilised on GQDs modified glassy carbon electrode (GCE). Transmission electron microscope, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used for characterising the electrochemical biosensor. The developed biosensor responds efficiently to UA presence over the concentration linear range 1–800 μM with the detection limit 0.3 μM. This novel biosensing platform based on UOx/GQDs electrode responded even more sensitively than that based on GCE modified by UOx alone. The inexpensive, reliable and sensitive sensing platform based on UOx/GQDs electrode provides wide potential applications in clinical.Inspec keywords: organic compounds, graphene devices, quantum dots, enzymes, biosensors, biochemistry, electrochemical electrodes, electrochemical sensors, transmission electron microscopy, scanning electron microscopy, voltammetry (chemical analysis), electrochemical impedance spectroscopy, nanomedicine, molecular biophysicsOther keywords: sensitive uric acid determination, graphene quantum dots, uric oxidase immobilisation, electrochemical detection, GQD, enzyme immobilisation, glassy carbon electrode, GCE, transmission electron microscope, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, electrochemical biosensor, C     

Amperometric L-lactate sensor based on sol-gel processing of an enzyme-linked silicon alkoxide

A novel organically modified silica material has been prepared by covalent linking of the carboxylic acid group of lactate dehydrogenase to the amino group of an organoalkoxysilane precursor via a carbodiimide coupling reaction during the sol-gel process. The material was used to fabricate a leak-free biosensor. The experimental variables and characteristics of the biosensors were studied by electrochemical methods. Results showed that the coenzyme concentration, mediator concentration, and electrode rotation speed will influence the sensitivity of the biosensor. The biosensors exhibited high sensitivity (1.47 microA/mM), low detection limit (1.5 microM), reasonable apparent activity (1.31 min(-1)), good fabrication reproducibility, and good long-term operational stability (approximately 1 week).     

A strategy for the ultrasensitive detection of cancer biomarkers based on the LSPR response of a single AuNP

A biosensor based on the localized surface plasmon resonance (LSPR) response of a single Au nanoparticle was fabricated for the highly sensitive detection and quantification of a specific cancer biomarker. The spectral position changes of single Au nanoparticles induced by the binding of adsorbates and target analytes were effectively utilized as sensing tools. The LSPR responses of single Au nanoparticles were obtained by tracking the wavelength shift of the corresponding resonant Rayleigh light scattering spectra via dark-field microspectroscopy. Using prostate specific antigen as a model, an LSPR lambda max shift of about 2.75 nm was recorded by a primary immunoresponse corresponding to 0.1 pg/mL of the target antigen. The sensitivity of the immunoassay can be substantially enhanced, however, by a sandwich strategy. A PSA polyclonal antibody was used as an amplifying agent in the strategy. As a result, the linear dynamic range of the sensing platform was determined to be within the concentration range of 10(-4) to 0.1 ng/mL and a detectable minimum concentration of 0.1 pg/mL was identified, with an LSPR lambda max shift of about 4.96 nm. The results indicate that the aforementioned approach can significantly contribute to the fabrication of ultrasensitive biosensors, allowing the quantitative analysis of cancer-associated proteins     

Organic thin-film transistors for chemical and biological sensing

Organic thin-film transistors (OTFTs) show promising applications in various chemical and biological sensors. The advantages of OTFT-based sensors include high sensitivity, low cost, easy fabrication, flexibility and biocompatibility. In this paper, we review the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistors (OECTs), mainly focusing on the papers published in the past 10 years. Various types of OTFT-based sensors, including pH, ion, glucose, DNA, enzyme, antibody-antigen, cell-based sensors, dopamine sensor, etc., are classified and described in the paper in sequence. The sensing mechanisms and the detection limits of the devices are described in details. It is expected that OTFTs may have more important applications in chemical and biological sensing with the development of organic electronics.     

Enzyme biosensor based on plasma-polymerized film-covered carbon nanotube layer grown directly on a flat substrate

We report a novel approach to fabrication of an amperometric biosensor with an enzyme, a plasma-polymerized film (PPF), and carbon nanotubes (CNTs). The CNTs were grown directly on an island-patterned Co/Ti/Cr layer on a glass substrate by microwave plasma enhanced chemical vapor deposition. The as-grown CNTs were subsequently treated by nitrogen plasma, which changed the surface from hydrophobic to hydrophilic in order to obtain an electrochemical contact between the CNTs and enzymes. A glucose oxidase (GOx) enzyme was then adsorbed onto the CNT surface and directly treated with acetonitrile plasma to overcoat the GOx layer with a PPF. This fabrication process provides a robust design of CNT-based enzyme biosensor, because of all processes are dry except the procedure for enzyme immobilization. The main novelty of the present methodology lies in the PPF and/or plasma processes. The optimized glucose biosensor revealed a high sensitivity of 38 μA mM(-1) cm(-2), a broad linear dynamic range of 0.25-19 mM (correlation coefficient of 0.994), selectivity toward an interferent (ascorbic acid), and a fast response time of 7 s. The background current was much smaller in magnitude than the current due to 10 mM glucose response. The low limit of detection was 34 μM (S/N = 3). All results strongly suggest that a plasma-polymerized process can provide a new platform for CNT-based biosensor design.     

Silicon nanowire arrays for label-free detection of DNA

Arrays of highly ordered n-type silicon nanowires (SiNW) are fabricated using complementary metal-oxide semiconductor (CMOS) compatible technology, and their applications in biosensors are investigated. Peptide nucleic acid (PNA) capture probe-functionalized SiNW arrays show a concentration-dependent resistance change upon hybridization to complementary target DNA that is linear over a large dynamic range with a detection limit of 10 fM. As with other SiNW biosensing devices, the sensing mechanism can be understood in terms of the change in charge density at the SiNW surface after hybridization, the so-called "field effect". The SiNW array biosensor discriminates satisfactorily against mismatched target DNA. It is also able to monitor directly the DNA hybridization event in situ and in real time. The SiNW array biosensor described here is ultrasensitive, non-radioactive, and more importantly, label-free, and is of particular importance to the development of gene expression profiling tools and point-of-care applications.     

A comparative study of enzyme immobilization strategies for multi-walled carbon nanotube glucose biosensors

This work addresses the comparison of different strategies for improving biosensor performance using nanomaterials. Glucose biosensors based on commonly applied enzyme immobilization approaches, including sol-gel encapsulation approaches and glutaraldehyde cross-linking strategies, were studied in the presence and absence of multi-walled carbon nanotubes (MWNTs). Although direct comparison of design parameters such as linear range and sensitivity is intuitive, this comparison alone is not an accurate indicator of biosensor efficacy, due to the wide range of electrodes and nanomaterials available for use in current biosensor designs. We proposed a comparative protocol which considers both the active area available for transduction following nanomaterial deposition and the sensitivity. Based on the protocol, when no nanomaterials were involved, TEOS/GOx biosensors exhibited the highest efficacy, followed by BSA/GA/GOx and TMOS/GOx biosensors. A novel biosensor containing carboxylated MWNTs modified with glucose oxidase and an overlying TMOS layer demonstrated optimum efficacy in terms of enhanced current density (18.3 ± 0.5 μA mM(-1) cm(-2)), linear range (0.0037-12 mM), detection limit (3.7 μM), coefficient of variation (2%), response time (less than 8 s), and stability/selectivity/reproducibility. H(2)O(2) response tests demonstrated that the most possible reason for the performance enhancement was an increased enzyme loading. This design is an excellent platform for versatile biosensing applications.     

Disposable biosensor based on Au nanoparticles-modified CdS nanorod arrays for detection cytochrome c

A novel disposable biosensor is developed based on gold nanoparticles modified CdS nanorod arrays. The ordered CdS nanorod arrays firstly have been synthesized by a simple hydrothermal method. Then, the CdS nanorod arrays are modified by gold nanoparticles, which are directly fabricated into an electrode for detection of cytochrome c (Cyc) in solution without any pretreatment. The modified CdS nanorod arrays biosensor with the immense surface area and high electrical conductivity shows a good sensitivity and linear range. This method may be used to construct other electrochemical biosensors using aligned nanorod/nanowire films.     

Multifunctional label-free electrochemical biosensor based on an integrated aptamer

Aptamers, which are in vitro selected functional oligonucleotides, have been employed to design novel biosensors (i.e., aptasensors) due to their inherent selectivity, affinity, and their multifarious advantages over traditional recognition elements. In this work, we reported a multifunctional reusable label-free electrochemical biosensor based on an integrated aptamer for parallel detection of adenosine triphosphate (ATP) and alpha-thrombin, by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A Au electrode as the sensing surface was modified with a part DNA duplex which contained a 5'-thiolated partly complementary strand (PCS) and a mixed aptamer (MBA). The unimolecular MBA contained small-molecule ATP binding aptamer (ABA) and also protein alpha-thrombin binding aptamer (TBA). Thus, the aptasensor could be used for detection of ATP and alpha-thrombin both. The detection limit of ATP was 1 x 10(-8) M, and its detection range could extend up to 10(-4) M, whereas the detection limit of alpha-thrombin was 1 x 10(-11) M, and its detection range was from 1 x 10(-11) to 1 x 10(-7) M. Meanwhile, after detecting alpha-thrombin, the sensing interface could be used for ATP recognition as well. The aptasensor regeneration could be realized by rehybridizing of the MBA strand with the partly complementary strand immobilized on the Au surface after ATP detection or by treating with a large amount of ATP and then rehybridizing the MBA strand with the partly complementary strand immobilized on the Au surface after alpha-thrombin detection. The aptasensor fabricated exhibited several advantages such as label-free detection, high sensitivity, regeneration, and multifunctional recognition. It also showed the detectability in biological fluid. Therein it held promising potential for integration of the sensing ability such as the simultaneous detection for multianalysis in the future.