Biomolecule-nanoparticle hybrid systems for bioelectronic applications

Recent advances in nanobiotechnology involve the use of biomolecule-nanoparticle (NP) hybrid systems for bioelectronic applications. This is exemplified by the electrical contacting of redox enzymes by means of Au-NPs. The enzymes, glucose oxidase, GOx, and glucose dehydrogenase, GDH, are electrically contacted with the electrodes by the reconstitution of the corresponding apo-proteins on flavin adenine dinucleotide (FAD) or pyrroloquinoline quinone (PQQ)-functionalized Au-NPs (1.4 nm) associated with electrodes, respectively. Similarly, Au-NPs integrated into polyaniline in a micro-rod configuration associated with electrodes provides a high surface area matrix with superior charge transport properties for the effective electrical contacting of GOx with the electrode. A different application of biomolecule-Au-NP hybrids for bioelectronics involves the use of Au-NPs as carriers for a nucleic acid that is composed of hemin/G-quadruplex DNAzyme units and a detecting segment complementary to the analyte DNA. The functionalized Au-NPs are employed for the amplified DNA detection, and for the analysis of telomerase activity in cancer cells, using chemiluminescence as a readout signal. Biomolecule-semiconductor NP hybrid systems are used for the development of photoelectrochemical sensors and optoelectronic systems. A hybrid system consisting of acetylcholine esterase (AChE)/CdS-NPs is immobilized in a monolayer configuration on an electrode. The photocurrent generated by the system in the presence of thioacetylcholine as substrate provides a means to probe the AChE activity. The blocking of the photocurrent by 1,5-bis(4-allyldimethyl ammonium phenyl)pentane-3-one dibromide as nerve gas analog enables the photoelectrochemical analysis of AChE inhibitors. Also, the association CdS-NP/double-stranded DNA hybrid systems with a Au-electrode, and the intercalation of methylene blue into the double-stranded DNA, generates an organized nanostructure of switchable photoelectrochemical functions. Electrochemical reduction of the intercalator to the leuco form, -0.4 V vs. SCE, results in a cathodic photocurrent as a result of the transfer of photoexcited conduction-band electrons to O(2) and the transport of electrons to the valance-band holes by the reduced intercalator units. The oxidation of the intercalator, E 0 V (vs. SCE), yields in the presence of triethanolamine, TEOA, as sacrificial electron donor, an anodic photocurrent by the transport of conduction-band electrons, through intercalator units, to the electrodes, and filling the valance-band holes with electrons supplied by TEOA. The systems reveal potential-switchable directions of the photocurrents, and reveal logic gate functions.     

Renewable dehydrogenase-based interfaces for bioelectronic applications

Bioelectronic interfaces that establish electrical communication between redox enzymes and electrodes have potential applications as biosensors, biocatalytic reactors, and biological fuel cells. However, these interfaces contain labile components, including enzymes and cofactors, which have limited lifetimes and must be replaced periodically to allow long-term operation. Current methods to fabricate bioelectronic interfaces do not allow facile replacement of these components, thus limiting the useful lifetime of the interfaces. In this paper we describe a versatile new fabrication approach that binds the enzymes and cofactors using reversible ionic interactions. This approach allows the interface to be removed via a simple pH change and then replaced to fully regenerate the biocatalytic activity. The positively charged polyelectrolyte poly(ethylenimine) was used to ionically bond a dehydrogenase enzyme and its cofactor to a gold electrode that was functionalized with 3-mercaptopropionic acid and the electron mediator toluidine blue O. By reducing the pH, the surface-bound 3-mercaptopropionic acid was protonated, disrupting the ionic bonds and releasing the enzyme-modified polyelectrolyte. After neutralization, fresh enzyme and cofactor were bound, regenerating the bioelectronic interface. Cyclic voltammetry, chronoamperometry, constant potential amperometry, electrochemical impedance spectroscopy, and Fourier transform infrared spectroscopy analyses were used to characterize the bioelectronic interfaces. For the two enzymes tested (secondary alcohol dehydrogenase and sorbitol dehydrogenase) and their respective cofactors (beta-nicotinamide adenine dinucleotide phosphate and beta-nicotinamide adenine dinucleotide), the reconstituted interface exhibited a surface coverage, an electron-transfer coefficient, and a turnover rate similar to those of the original interface.     

Organic single crystals or crystalline micro/nanostructures: Preparation and field-effect transistor applications

Organic single crystals hold great promise for the development of organic semiconductor materials, because they could reveal the intrinsic electronic properties of these materials, providing high-performance electronic devices and probing the structure-property relationships. This article reviews the preparation methods for organic single crystals or crystalline micro/nanostructures, including vapor phase growth methods and solution-processed methods, and summarizes a few methods employed in the fabrication of field-effect transistors along with dozens of examples concerning both small molecules and polymers with high field-effect performance.     

Adaptive nanowire-nanotube bioelectronic system for on-demand bioelectrocatalytic transformations

An integrated nanobioelectronic system, exploiting the distinct properties of nanowires and carbon-nanotubes, has been designed for triggering reversibly and on-demand bioelectrocatalytic transformations of alcohols.     

p-Channel organic semiconductors based on hybrid acene-thiophene molecules for thin-film transistor applications

We report the structural and electrical characterization of two new p-channel organic semiconductors, 5,5'-bis(2-tetracenyl)-2,2'-bithiophene (1) and 5,5'-bis(2-anthracenyl)-2,2'-bithiophene (2). Both compounds exhibited a high degree of thermal stability with decomposition temperatures of 530 degrees C and 425 degrees C for 1 and 2, respectively. The thin-film structures of 1 and 2 were examined using wide-angle X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXD), and atomic force microscopy (AFM). Films of 1 and 2 pack in similar triclinic unit cells with the long axes of the molecules nearly perpendicular to the substrate. Thin-film transistors (TFTs) based on 1 and 2 exhibit contact-corrected linear regime hole mobility as high as 0.5 cm2/Vs and 0.1 cm2/Vs, respectively. The specific contact resistance at high gate voltages for gold top contacts was 2 x 10(4) Ohms cm and 3 x 10(4) Ohms cm for 35 nm thick films of 1 and 2, respectively. Long-term air stability tests revealed less degradation of the electrical properties of 1 and 2 in comparison to pentacene. Variable temperature measurements revealed activation energies as low as 22 and 27 meV for 1 and 2, respectively. The temperature and gate voltage dependence of the mobility are discussed in terms of a double exponential distribution of trap states and a model accounting for the layered structure of the organic films. The enhanced air and thermal stability over pentacene, combined with good electrical performance characteristics, make 2 a promising candidate for future organic TFT applications.     

Microfabrication of three-dimensional bioelectronic architectures

The functionality and structural diversity of biological macromolecules has motivated efforts to exploit proteins and DNA as templates for synthesis of electronic architectures. Although such materials offer promise for numerous applications in the fabrication of cellular interfaces, biosensors, and nanoelectronics, identification of techniques for positioning and ordering bioelectronic components into useful patterns capable of sophisticated function has presented a major challenge. Here, we describe the fabrication of electronic materials using biomolecular scaffolds that can be constructed with precisely defined topographies. In this approach, a tightly focused pulsed laser beam capable of promoting protein photo-cross-linking in specified femtoliter volume elements is scanned within a protein solution, creating biomolecular matrices that either remain in integral contact with a support surface or extend as free-standing structures through solution, tethered at their ends. Once fabricated, specific protein scaffolds can be selectively metallized via targeted deposition and growth of metal nanoparticles, yielding high-conductivity bioelectronic materials. This aqueous fabrication strategy opens new opportunities for creating electronic materials in chemically sensitive environments and may offer a general approach for creating microscopically defined inorganic landscapes.     

Organic permeable base light-emitting transistor: a new concept device architecture for display technology

正As an important part of the information industry,display technology has been playing a very important role in the development of information technology.Due to the obvious advantages in thickness,color gamut,view angle and contrast ratio,organic light-emitting diodes (OLEDs) are recognized as one of the most important display technologies and have been successfully commercialized in mobile phones and TVs.However,the detrimental complex device fabrication processes and high operation voltage required by drive transistor backplanes for OLED active-matrix displayssignificantly prevent their wider applications.     

Nanocrystal-based bioelectronic coding of single nucleotide polymorphisms

A bioelectronic method for coding unknown single nucleotide polymorphisms (SNPs) based on the use of different encoding nanocrystals is described. Four such nanocrystals, ZnS, CdS, PbS, and CuS, linked to the adenosine, cytidine, guanosine and thymidine mononucleotides, respectively, are sequentially introduced to the DNA hybrid-coated magnetic-bead solution. Each mutation captures via base pairing different nanocrystal-mononucleotide conjugates, and yields a characteristic multipotential voltammogram, whose peak potentials reflect the identity of the mismatch. The mismatch recognition events are being amplified by the metal accumulation feature of the stripping voltammetric transduction mode. Each of the eight possible one-base mismatches can thus be identified in a single voltammetric run. The use of nanocrystal tracers for detecting two known mutations in a single DNA target is also illustrated in connection to nanocrystals linked to two nucleotides along with a single voltammetric run. The protocol presented should facilitate the rapid, simple, low-cost, and high throughput screening for SNPs.     

Ultrasensitive bioelectronic devices based on conducting polymers for electrophysiology studies

Conducting polymer electrodes based on poly(3,4-ethylenedioxythiophene doped with poly(styrenesulfonate) (PEDOT:PSS) are evaluated as transducers to record extracellular signals in cell populations. The performance of the polymer electrode is compared with a gold electrode. A small-signal impedance analysis shows that in the presence of an electrolyte, the polymer electrode establishes for frequencies below 100 Hz a higher capacitive electrical double layer at the electrode/electrolyte interface. Furthermore, the polymer/electrolyte interfacial resistance is several orders of magnitude lower than the resistance of the gold/electrolyte interface. The polymer low interfacial resistance minimizes the intrinsic thermal noise and increases the system sensitivity. The ultra-sensitivity of the polymer-based transducer system was demonstrated by recording the electrical activity of cancer cells of the nervous system.     

Fluorene based donor‐acceptor polymer electrets for nonvolatile organic transistor memory device applications

Fluorene based donor‐acceptor polyimides, including poly[bis‐(4‐aminophenyl)fluorene‐hexanediamide] [PA(BAP F‐AC)], poly[bis‐(4‐aminophenyl)fluorene‐hexafluoroisopropylidenediphthalimide] [PI(BAPF‐6FDA)], poly[bis‐(4‐aminophenyl)fluorene‐oxydiphthalimide] [PI(BAPF‐ODPA)], and poly[bis‐(4‐aminophenyl)fluorene‐1,2,4,5‐cyclohexanetetracarboxylic diimide] [PI(BAPF‐HPMDA)], as charge storage layer (electret) are employed for nonvolatile memory device applications. The polyimides are consisted of electron‐donating fluorene diamine moiety (BAPF) and neutral (AC and HPMDA) or electron‐accepting (6FDA and ODPA) moieties, respectively. The memory characteristics of these devices can be tuned from the EORM (erase once and read many times) behavior [PA(BAPF‐AC)], semi‐flash [PI(BAPF‐ODPA)], [PI(BAPF‐HPMDA)], to a flash type memory [PI(BAPF‐6FDA)]. The PI(BAPF‐6FDA) devices show the largest memory window of 77 V and a long retention time over 10⁴ s with a high I_on/I_off current ratio of 10⁸. This is attributed to the largest torsion angle of PI(BAPF‐6FDA) stabilizing charge transfer (CT) complexes. The write‐read‐erase‐read cycles were stably operated over 100 cycles. This work provides a new insight into the relationship between the CT effect and the nonvolatile memory behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 602–614     

Organic heterostructures composed of one-and two-dimensional polymorphs for photonic applications

Organic heterostructures(OHSs) consist of organic micro/nanocrystals are of essential importance for the construction of integrated optoelectronics in the future. However, the scarcity of materials and the problem of phase separation still hinder the fine synthesis of OHSs. Herein, based on the α phase one-dimensional(1D) microrods and the β phase 2D microplates of one organic compound 3,3′-((1 E,1′E)-anthracene-9,10-diylbis(ethane-2,1-diyl))dibenzonitril(m-B_2BCB), we facilely synthesized the OHSs composed of these two polymorph phases, whose growth mechanism is attributed to the low lattice mismatch rate of5.8% between(001) plane of α phase(trunk) and(010) crystal plane of β phase(branch). Significantly, the multiport in/output channels can be achieved in the OHSs, which demonstrates the structure-dependent optical signals with the different output channels in the OHSs. Therefore, our experiment exhibits the great prospect of polymorphism in OHSs, which could provide further applications on multifunctional organic integrated photonics circuits.     

Organic thin-film transistors as transducers for (bio) analytical applications

The use of organic thin-film transistors (OTFTs) in sensorics is relatively new. Although electronic noses, electronic textiles and disposable biochemical sensors appear to be viable applications for this type of devices, the benefits of the technology still have to be proven. This paper aims to provide a review of the recent advances in the area of chemically sensitive field-effect devices based on organic thin-film transistors (OTFTs), with emphasis on bioanalytical applications. Detection principle, device configuration, materials and fabrication processes as well as sensor performances will be discussed, with emphasis on the potential for implementation in real applications and the important challenges ahead.     

Organic dyes with a novel anchoring group for dye-sensitized solar cell applications

Two novel trialkylsilyl-containing organic sensitizers (JK-53 and JK-54) have been designed and synthesized. Nanocrystalline TiO₂–silica-based dye-sensitized solar cells (DSSCs) were fabricated using these dyes. Under standard global AM 1.5 solar conditions, the JK-53-sensitized cell gave a short-circuit photocurrent density (J_sc) of 6.37 mA cm^?2, an open-circuit voltage (V_oc) of 0.70 V, and a fill factor of 0.74. These values correspond to an overall conversion efficiency (η) of 3.31%. By comparison, the JK-54-sensitized cell resulted in a J_sc of 7.52 mA cm^?2, a V_oc of 0.71 V, and a fill factor of 0.75. These values give an overall conversion efficiency of 4.01%.     

Silver nanocoral structures on electrodes: a suitable platform for protein-based bioelectronic devices

We report a simple strategy for constructing silver coral-like nanostructures on graphite electrodes suitable for bioelectronic applications. The nanocorals are conductive, have dimensions adequate for high protein loading, and are remarkably stable. They also provide a strong Raman surface enhancement that allows for in situ structural characterization of the immobilized proteins. The potential of the Ag nanocoral electrodes is exemplified by the construction and characterization of a hydrogen peroxide amperometric sensor based on cytochrome c.     

Organic nanoparticles from microemulsions: Formation and applications

Microemulsions have already been recognized as convenient templates for nanoparticle synthesis. Spontaneous formation of the compartmentalized domains within the microemulsions leads to facile and low-cost preparation processes.In the past, microemulsions were mainly explored as precursors for the synthesis of inorganic nanoparticles. However, there is a constantly growing number of publications offering to exploit these systems to produce organic nanoparticles, and in recent years, a variety of methods have emerged in this field. The aim of this review is to survey the methods recently used to produce organic nanomaterials from microemulsions, and to give a perspective on particle design possibilities that can be achieved by various techniques. The structure of the initial microemulsion system, the chemical and technical aspects of preparation, the nature of additives and surface active agents, as well as the possible outcomes in terms of final particle characteristics, will be discussed for the various methods.     

Highly sensitive disposable nucleic acid biosensors for direct bioelectronic detection in raw biological samples

The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1 nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25 pM (0.25 fmol) and 100 pM (1 fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000 CFU μL⁻¹ in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24 h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests.     

Graphene as a spacer to layer-by-layer assemble electrochemically functionalized nanostructures for molecular bioelectronic devices

This study demonstrates the capability of graphene as a spacer to form electrochemically functionalized multilayered nanostructures onto electrodes in a controllable manner through layer-by-layer (LBL) chemistry. Methylene green (MG) and positively charged methylimidazolium-functionalized multiwalled carbon nanotubes (MWNTs) were used as examples of electroactive species and electrochemically useful components for the assembly, respectively. By using graphene as the spacer, the multilayered nanostructures of graphene/MG and graphene/MWNT could be readily formed onto electrodes with the LBL method on the basis of the electrostatic and/or π-π interaction(s) between graphene and the electrochemically useful components. Scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), and cyclic voltammetry (CV) were used to characterize the assembly processes, and the results revealed that nanostructure assembly was uniform and effective with graphene as the spacer. Electrochemical studies demonstrate that the assembled nanostructures possess excellent electrochemical properties and electrocatalytic activity toward the oxidation of NADH and could thus be used as electronic transducers for bioelectronic devices. This potential was further demonstrated by using an alcohol dehydrogenase-based electrochemical biosensor and glucose dehydrogenase-based glucose/O(2) biofuel cell as typical examples. This study offers a simple route to the controllable formation of graphene-based electrochemically functionalized nanostructures that can be used for the development of molecular bioelectronic devices such as biosensors and biofuel cells.     

Effect of molecular weight in diketopyrrolopyrrole‐based polymers in transistor and photovoltaic applications

Uncovering the precise effect of the conjugated polymer chain length on the semiconducting properties in thin‐film devices is confounded by the step‐growth polymerization techniques typically used. Here, we use preparatory size exclusion chromatography to isolate fractions of two diketopyrrolopyrrole‐thiophene based co‐polymers with low molar‐mass dispersity, ?_M, and number average molecular weights up to 180 kDa. We find that the charge carrier mobility can vary over three orders of magnitude in the range from 9 to 70 kDa, while a factor of 3–4 increase in photovoltaic performance was noted over the same range. The effect of ?_M was found to be most drastic when the largest chains were mixed with the shortest. The study of the thin‐film morphology and crystallinity by GIWAXS give further insights into the origin of these effects. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2245–2253