Stability of polymer thin-film transistors based on poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene)

Polymer thin-film transistors (PTFTs) based on poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) semiconductor are fabricated by spin-coating process and characterized. In the experiments, solution preparation, deposition and device measurements are all performed in air for large-area applications. Hysteresis effect and gate-bias stress effect are observed for the devices at room temperature. The saturation current decreases and the threshold voltage shifts toward the negative direction upon gate-bias stress, but carrier mobility hardly changes. By using quasi-static C-V analysis for MOS capacitor structure, it can be deduced that the origin of threshold-voltage shift upon negative gate-bias stress is predominantly associated with hole trapping within the SiO₂ gate dielectric near the SiO₂/MEH-PPV interface due to hot-carrier emission.     

Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: A review

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.     

交流阻抗法在细胞分析中应用的研究进展

交流阻抗法作为一种新型的无标记、全程动态、实时分析方法已在细胞研究中得到了广泛应用。本文综述了基于交流阻抗法进行细胞分析的研究新进展,重点对非法拉第阻抗谱法和法拉第阻抗谱法用于细胞分析的原理及应用进行了总结,主要包括交流阻抗法在细胞形态、细胞生长、细胞增殖、细胞凋亡以及作用于细胞的药效和毒性研究中的应用,并对其发展趋势进行了展望。     

Electrogenerated chemiluminescence biosensing for the detection of prostate PC-3 cancer cells incorporating antibody as capture probe and ruthenium complex-labelled wheat germ agglutinin as signal probe

A highly selective and sensitive electrogenerated chemiluminescence (ECL) biosensor for the detection of prostate PC-3 cancer cells was designed using a prostate specific antibody as a capture probe and ruthenium complex-labelled wheat germ agglutinin as a signal probe. The ECL biosensor was fabricated by covalently immobilising the capture probe on a graphene oxide-coated glassy carbon electrode. Target PC-3 cells were selectively captured on the surface of the biosensor, and then, the signal probe was bound with the captured PC-3 cells to form a sandwich. In the presence of tripropylamine, the ECL intensity of the sandwich biosensor was logarithmically directly proportion to the concentration of PC-3 cells over a range from 7.0 × 10² to 3.0 × 10⁴ cells mL⁻¹, with a detection limit of 2.6 × 10² cells mL⁻¹. The ECL biosensor was also applied to detect prostate specific antigen with a detection limit of 0.1 ng mL⁻¹. The high selectivity of the biosensor was demonstrated in comparison with that of a lectin-based biosensor. The strategy developed in this study may be a promising approach and could be extended to the design of ECL biosensors for highly sensitive and selective detection of other cancer-related cells or cancer biomarkers using different probes.     

Bioanalytical applications of isothermal nucleic acid amplification techniques

The most popular in vitro nucleic acid amplification techniques like polymerase chain reaction (PCR) including real-time PCR are costly and require thermocycling, rendering them unsuitable for uses at point-of-care. Highly efficient in vitro nucleic acid amplification techniques using simple, portable and low-cost instruments are crucial in disease diagnosis, mutation detection and biodefense. Toward this goal, isothermal amplification techniques that represent a group of attractive in vitro nucleic acid amplification techniques for bioanalysis have been developed. Unlike PCR where polymerases are easily deactivated by thermally labile constituents in a sample, some of the isothermal nucleic acid amplification techniques, such as helicase-dependent amplification and nucleic acid sequence-based amplification, enable the detection of bioanalytes with much simplified protocols and with minimal sample preparations since the entire amplification processes are performed isothermally. This review focuses on the isothermal nucleic acid amplification techniques and their applications in bioanalytical chemistry. Starting off from their amplification mechanisms and significant properties, the adoption of isothermal amplification techniques in bioanalytical chemistry and their future perspectives are discussed. Representative examples illustrating the performance and advantages of each isothermal amplification technique are discussed along with some discussion on the advantages and disadvantages of each technique.     

A biosensor prepared by co-entrapment of a glucose oxidase and a carbon nanotube within an electrochemically deposited redox polymer multilayer

A glucose biosensor based on a nanocomposite made by layer-by-layer electrodeposition of the redox polymer into a multilayer containing glucose oxidase (GOx) and single-walled carbon nanotubes (SWCNT) on a screen-printed carbon electrode (SPCE) surface was developed. The objectives of the electrodeposition of redox polymer are to stabilize further the multilayer using a coordinative cross-linked redox polymer and to wire the GOx. The electrochemistry of the layer-by-layer assembly of the GOx/SWCNT/redox polymer nanocomposite was followed by cyclic voltammetry. The resultant biosensor provided stable and reproducible electrocatalytic responses to glucose, and the electrocatalytic current for glucose oxidation was enhanced with an increase in the number of layers. The biosensor displayed a linear range from 0.5 to 6.0mM, a sensitivity of 16.4μA/(mMcm(2)), and a response time of about 5s. It shows no response to 0.05mM of ascorbic acid, 0.32mM of uric acid and 0.20mM of acetaminophen using a Nafion membrane covering the nanocomposite-modified electrode surface.     

Modern mass spectrometry in the characterization and degradation of biodegradable polymers

In the last decades, the solid-waste management related to the extensively growing production of plastic materials, in concert with their durability, have stimulated increasing interest in biodegradable polymers. At present, a variety of biodegradable polymers has already been introduced onto the market and can now be competitive with non biodegradable thermoplastics in different fields (packaging, biomedical, textile, etc.). However, a significant economical effort is still directed in tailoring structural properties in order to further broaden the range of applications without impairing biodegradation. Improving the performance of biodegradable materials requires a good characterization of both physico-chemical and mechanical parameters. Polymer analysis can involve many different features including detailed characterization of chemical structures and compositions as well as average molecular mass determination. It is of outstanding importance in troubleshooting of a polymer manufacturing process and for quality control, especially in biomedical applications. This review describes recent trends in the structural characterization of biodegradable materials by modern mass spectrometry (MS). It provides an overview of the analytical tools used to evaluate their degradation. Several successful applications of MALDI-TOF MS (matrix assisted laser desorption ionization time of flight) and ESI MS (electrospray mass spectrometry) for the determination of the structural architecture of biodegradable macromolecules, including their topology, composition, chemical structure of the end groups have been reported. However, MS methodologies have been recently applied to evaluate the biodegradation of polymeric materials. ESI MS represents the most useful technique for characterizing water-soluble polymers possessing different end group structures, with the advantage of being easily interfaced with solution-based separation techniques such as high-performance liquid chromatography (HPLC).