Recent Advances in Electropolymerized Conducting Polymers in Amperometric Biosensors

Conducting electroactive polymers (CPs) are materials discovered just over 20 years ago which have aroused considerable interest on account of their electronic conducting properties and unique chemical and biochemical properties. Consequently, they have numerous (bio)analytical and technological applications. CPs are easily synthesized and deposited onto the conductive surface of a given substrate from monomer solutions by electrochemical polymerization with precise electrochemical control of their formation rate and thickness. Coating electrodes with CPs under mild conditions opens up enormous possibilities for the immobilization of biomolecules and bioaffinity or biorecognizing reagents, the improvement of their electrocatalytic properties, rapid electron transfer and direct communication to produce a range of analytical signals and new analytical applications. Co-immobilization of other molecules (enzymatic co-factors or charge-transfer mediators) by entrapment within electropolymerized films or by covalent binding on these films permits straightforward fabrication of reagentless biosensors. The characteristics of CPs and their uses, mainly in amperometric biosensors, are reviewed. The most recent applications and lines of research related to CP films are summarized in the different sections of the paper, and probable future trends are discussed.     

Ultra-Shallow Chemical Characterization of Organic Thin Films Deposited by Plasma and Vacuum-Ultraviolet, Using Angle- and Excitation Energy-Resolved XPS

Nitrogen (N)-rich organic thin films were deposited using both low-pressure plasma- and vacuum-ultraviolet-based techniques, from mixtures of ammonia (NH₃) and ethylene (C₂H₄). These films were investigated using angle-resolved and excitation energy resolved X-ray photoelectron spectroscopy (ARXPS and ERXPS, respectively) in order to determine their sub-surface chemical profiles. These two techniques enable one to tune the ??XPS 95%?? information depth, z _95%, by varying either the angle or the excitation energy. Using a combination of both techniques, z _95% can be varied continuously from 0.7 to 11 nm. The surface-near chemistry is investigated using both high-resolution C 1s spectra and elemental concentrations derived from elemental peak intensities. Results show that while laboratory XPS, and even ARXPS, suggest homogenous surface chemistries, the novel combination of ARXPS and ERXPS points to the existence of a compositional profile in the extreme outer surface layer. Our conclusions are supported by simulations using SESSA software.     

Consumer price sensitivity in the retail industry: Latitude of acceptance with heterogeneous demand

Estimating the effect of price changes on demand is an essential task for retailers. This study proposes a methodology based on consumer utility for modeling the price thresholds phenomenon that allows for threshold asymmetry, incorporates consumer heterogeneity and uses weekly aggregated brand-level data. Unlike other studies based on consumer utility models, which generate results only for the price elasticity of market share, a methodology for estimating price elasticity of demand is also included. Data on fast-moving goods (detergents, toilet paper, soft drinks, meats, liquid juices and yogurts) supplied by a major retail chain are used to demonstrate the existence of price thresholds and their effects on price elasticity. In every case it was found that within the thresholds or latitude of acceptance, consumers are relatively less sensitive to price variations while beyond them a higher sensitivity was observed. In some cases a product brand was classified as inelastic within the latitude of acceptance and elastic outside of it.     

Design Strategies for Diradical Boron/Nitrogen Doped Carbon-Based Materials

New heterocyclic diradicaloids based on boron and nitrogen-doped polycyclic systems with open-shell ground-states are obtained via concomitant structural and quinoidal extensions, thus allowing to merge the best of both design strategies. A combination of experimental characterization and theoretical calculations have helped disclose their electronic structure, as well as rationalize their associated magnetic and photophysical properties, spanning the chemical space of available molecular templates for cutting-edge applications in organic electronics and spintronics.     

Photoactive Cryptands. Crystal Structure of the Sodium Cryptate of the Tris(phenanthroline) Macrobicyclic Ligand

The crystal structure of the complex [phen · phen · phen] · NaBr · 2 CHCl₃ of the macrobicyclic ligand 1 has been determined. The complex is of cryptate type, the Na⁺ cation being contained in the molecular cavity of 1 and coordinated to all eight N-atoms. The ligand has a propeller shape and interconverts in solution between the two enantiomeric helical forms.     

Photoactive cryptands. Synthesis of the sodium cryptates of macrobicyclic ligands containing bipyridine and phenoanthroline groups

The NaBr cryptates of five macrobicyclic ligands containing bipyridine (bpy) and phenanthroline (phen) groups, i.e, of [bpy.bpy.bpy] 1 [bpy.bpy.phen] 2 [phen.phen.-phen] 3 [2.1.phen] 4 and [2.2.phen] 5 , have been prepared. 1, 2, 4 and 5 have been obtained in high yield by condensation of bis(bromomethyl)bipyridine 6 or -phenanthroline 9 with the corresponding macrocyclic diamines in presence of Na₂CO₃. Direct access to the NaBr complexes of th symmetrical cryptands 1 and 3 was achieved by a one-step macrobicyclisation procedure. The metal-ion complexes of ligands 1-5 have the attractive feature of combining the cation inclusion, nature of cryptates with the photoactivity of bipyridine and phenanthroline groups; they may thus be expected to posses a variety of interesting physical and chemical properties.     

Temperature- and pH-sensitive interpenetrating polymer networks grafted on PP: Cross-linking irradiation dose as a critical variable for the performance as vancomycin-eluting systems

This work focuses on the effect of gamma-ray radiation conditions on the stimuli-responsiveness and drug-eluting performance of polypropylene (PP) substrates grafted with interpenetrating networks of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc). PNIPAAm was cross-linked applying 10–100 kGy doses in the presence and absence of the chemical cross-linker N,N′-methylenebisacrylamide (MBAAm). Then, the net-PP-g-PNIPAAm was interpenetrated with PAAc synthesized under a 2.5 kGy dose to obtain net-PP-g-PNIPAAm-inter-net-PAAc films. The amount of grafted PNIPAAm (80%, 125% and 145% levels) and the cross-linking radiation dose (10, 40 and 70 kGy levels) strongly determine the interpenetration of PAAc, the swelling degree, the amount of vancomycin loaded and its release rate. The chemical cross-linker only caused a minor decrease in the degree of swelling. The higher the PNIPAAm grafted on PP and the lower the cross-linking radiation dose, the more the PAAc in the IPN and, consequently, the higher the vancomycin loaded through specific interactions and the more sustained the release (>8 h). The films possessing these features exhibited vancomycin release rate per surface unit suitable to prevent bacterial growth. Thus, adequate tuning of the radiation doses during grafting and cross-linking of the PNIPAAm networks may enable to achieve surface-modified materials for medical devices with an antibiofilm performance.     

Enantiopure lanthanide complexes incorporating a tetraazatriphenylene sensitiser and three naphthyl groups: exciton coupling,intramolecular energy transfer,efficient singlet oxygen formation and perturbation by DNA binding

In cationic nine-coordinate chiral terbium and europium complexes incorporating exciton-coupled naphthyl groups and a tetraazatriphenylene sensitising chromophore, efficient intramolecular energy transfer occurs leading to population of the naphthyl triplet state. With the terbium complex, the absolute quantum yield of singlet oxygen formation is 51% (lambda(exc) 355 nm), and for the Eu complex the intensity of metal-based emission increases by up to 350% on binding to poly(dGdC) or calf-thymus DNA, and was greater for the delta-isomer.