(Electro)Sensing of Phenicol Antibiotics-A Review.

The presence of residues from frequent antibiotic use in animal feed can cause serious health risks by contaminating products meant for human consumption such as meat and milk. The present paper gives an overview of the electrochemical methods developed for the detection of phenicol antibiotic residues (chloramphenicol, thiamphenicol, and florfenicol) in different kinds of foodstuffs. Electrochemical sensors based on different biomolecules and nanomaterials are described. The detection limit of various developed methods with their advantages and disadvantages will be highlighted.

Sandwich double-decker lanthanide(III) "intracavity" complexes based on clamshell-type phthalocyanine ligands: synthesis, spectral, electrochemical, and spectroelectrochemical investigations.

Phthalocyanine compounds of novel type based on a bridged bis-ligand, denoted "intracavity" complexes, have been prepared. Complexation of clamshell ligand 1,1'-[benzene-1,2-diylbis(methanediyloxy)]bis[9(10),16(17),23(24)-tri-tert-butylphthalocyanine] ((clam,tBu)Pc(2)H(4), 1) with lanthanide(III) salts [Ln(acac)(3)]⋅n H(2)O (Ln = Eu, Dy, Lu; acetylacetonate) led to formation of double-deckers (clam,tBu)Pc(2)Ln (2 a-c). Formation of high molecular weight oligophthalocyanine complexes was demonstrated as well. The presence of an intramolecular covalent bridge affecting the relative arrangement of macrocycles was shown to result in specific physicochemical properties. A combination of UV/Vis/NIR and NMR spectroscopy, MALDI-TOF mass-spectrometry, cyclic voltammetry, and spectroelectrochemistry provided unambiguous characterization of the freshly prepared bis-phthalocyanines, and also revealed intrinsic peculiarities in the structure-property relationship, which were supported by theoretical calculations. Unexpected NMR activity of the paramagnetic dysprosium complex 2 b in the neutral π-radical form was observed and examined as well.

Purification and characterization of azurin from the methylamine-utilizing obligate methylotroph Methylobacillus flagellatus KT.

Methylamine dehydrogenase (MADH) and azurin were purified from the periplasmic fraction of the methylamine-grown obligate methylotroph Methylobacillus flagellatus KT. The molecular mass of the purified azurin was 16.3 kDa, as measured by SDS-PAGE, or 13 920 Da as determined by MALDI-TOF mass spectrometry. Azurin of M. flagellatus KT contained 1 copper atom per molecule and had an absorption maximum at 620 nm in the oxidized state. The redox potential of azurin measured at pH 7.0 by square-wave voltammetry was +275 mV versus normal hydrogen electrode. MADH reduced azurin in the presence of methylamine, indicating that this cupredoxin is likely to be the physiological electron acceptor for MADH in the electron transport chain of the methylotroph. A scheme of electron transport functioning in M. flagellatus KТ during methylamine oxidation is proposed.

Synthesis and characterization of heteroleptic rare earth double-decker complexes involving tetradiazepinoporphyrazine and phthalocyanine macrocycles.

Reaction of (2,3,9,10,16,17,23,24-octabutylphthalocyaninato)lanthanide(iii) acetylacetonates (BuPcLn(acac), 1a-c, Ln = Lu (a), Eu (b), La (c)) with a tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazine ligand (tBuPhDzPzH2, 2) produced sandwich compounds (tBuPhDzPz)Ln(BuPc) (3a-c), which represent the first heteroleptic double-deckers incorporating both Pc and DzPz decks. A combination of high-resolution mass spectrometry, UV-Vis/NIR, MCD, and 1H NMR spectroscopy, and square-wave voltammetry provided unambiguous characterization of target complexes 3 indicating that their spectral and electrochemical properties are generally intermediate with respect to their homoleptic relatives. Based on the data of solution-state 1H-1H NMR (COSY, NOESY) correlation spectroscopy supported by DFT calculations, a dimerization tendency of compounds 3 proportional to the Ln(iii) ion size was found. The spectroelectrochemical study of 3 and the corresponding homoleptic double-deckers revealed a pronounced tendency to aggregation of the one-electron oxidized forms of DzPz-containing double-decker complexes compared to homoleptic Pc2Ln compounds.

Optical readout of controlled monomer-dimer self-assembly.

5,7-Substituted 1,4-diazepinoporphyrazine magnesium(ii) complexes were synthesized via Mg(ii)-alkoxide templated macrocyclization. A single crystal growth synchrotron diffraction analysis permitted what is to our knowledge the first structural characterization of a 1,4-diazepinoporphyrazine. It exists as a dimer in the solid state. In silico calculations supported by solution phase spectral studies involving a series of representative derivatives, provided insights into the factors governing dimerization of 1,4-diazepinoporphyrazines. The present 1,4-diazepinoporphyrazines serve as useful probes for understanding the determinants that guide dimer-monomer equilibria and the self-assembly of phthalocyanine derivatives.

Double-decker bis(tetradiazepinoporphyrazinato) rare earth complexes: crucial role of intramolecular hydrogen bonding.

A series of homoleptic bis{tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato}lanthanide sandwich complexes [(tBuPh)DzPz]2Ln (Ln = Lu, Er, Dy, Eu, Nd, Ce, La) were prepared and their physicochemical properties were studied to gain insight into the nature of specific interactions in diazepinoporphyrazines. The effect of annulated diazepine moieties and the Ln ionic radius on the properties of the complexes was investigated in comparison with double-decker phthalocyanines. A combination of experimental and theoretical studies revealed the presence of two types of hydrogen bonding interactions in the metal-free porphyrazine and the corresponding sandwich complexes, namely, interligand C-H(ax)N(meso) hydrogen bonding and O-HN(Dz) ligand-water interaction. The interligand hydrogen bonding imparts high stability of the ligand dimer and the double-decker compounds in a reduced state. This work is the first comprehensive investigation into the fundamental understanding of the unusual properties of diazepine-containing macroheterocycles.

meso-Phenyltetrabenzotriazaporphyrin based double-decker lanthanide(III) complexes: synthesis, structure, spectral properties and electrochemistry.

A series of half-sandwich and sandwich-type lanthanide(III) complexes have been prepared using tetrabenzotriazaporphyrin ligands. Reaction of 27-phenyl-29H,31H-tetrabenzo[b,g,l,q][5,10,15]-triazaporphyrin (PhTBTAPH2, 1) with salts [LnX3]·nH2O (Ln = Eu (a), Lu (b); X = OAc, acac) afforded the single- and homoleptic double-deckers (PhTBTAP)LnOAc (2) and (PhTBTAP)2Ln (3) respectively. Heteroleptic double-decker compounds (PhTBTAP)LnPc (4a,b) were obtained upon interaction of 1 with the corresponding Ln mono(phthalocyaninates). An unexpected formation of partially and completely dephenylated co-products 5 and 6 has been detected in the synthesis of sandwich 3, while the possibility of the dearylation of the half-sandwich compound 2 has been demonstrated as well. A more predictable yet firstly observed formation of the triple-decker compound (PhTBTAP)3Eu2 (7) has also been found. Structural studies of 3 supported by 1H NMR spectra, XRD analysis and DFT theoretical calculations reveal that the Eu complex 3a is formed as a single isomer, while the lutetium compound 3b represents an inseparable mixture of two rotational isomers with virtually identical spectral characteristics. The double-decker compounds 3 and 4 reveal intrinsic UV-Vis/NIR absorption as well as peculiar electrochromic behavior. The heteroleptic derivatives 4 generally show intermediate spectral and electrochemical properties with respect to their homoleptic relatives.

Novel near-IR absorbing phenyl-substituted phthalo- and naphthalocyanine complexes of lanthanide(III): synthesis and spectral and electrochemical properties.

A series of novel phenyl-substituted planar and sandwich-type complexes of Eu, Er and Lu with phthalo and naphthalocyanine ligands was obtained. A successful synthesis of dinaphthalocyanines from the ligand is described. A selective synthetic approach to the phenyl-substituted triphthalocyanine complexes from the ligand and acetylacetonate salts of lanthanides was developed. Correlations between the ionic radii of the central metal and absorption maxima were obtained for sandwich-type complexes. It was found that intervalence (IV) bands for dinaphthalocyanine complexes were red-shifted about 200 nm in comparison with corresponding diphthalocyanines, reaching 1797 nm for the Eu complex. The electrochemical behaviour of planar and sandwich-type Lu complexes was investigated. For the first time a spectroelectrochemical study of multistep reduction and oxidation processes for a triple-decker complex was carried out using the example of the triphthalocyanine of Lu. The structures of the compounds obtained were determined by (1)H NMR and high resolution MALDI TOF/TOF. The first single-crystal structure for an aryl-substituted double-decker complex was described using the example of the diphthalocyanine of Lu, showing the presence of intramolecular π-π interactions between phenyl groups.

Bis(tetrabenzotriazaporphyrinato) and (tetrabenzotriazaporphyrinato)(phthalocyaninato) lutetium(III) complexes--novel sandwich-type tetrapyrrolic ligand based NIR absorbing electrochromes.

The first sandwich-type complexes have been prepared for tetrabenzotriazaporphyrin ligands. The compounds reveal intrinsic UV-Vis/NIR absorption as well as peculiar electrochromic behavior. The heteroleptic (tetrabenzotriazaporphyrinato)(phthalocyaninato) lutetium derivative shows intermediate spectral and electrochemical properties with respect to homoleptic relatives.

Development of a highly sensitive and robust Cor a 9 specific enzyme-linked immunosorbent assay for the detection of hazelnut traces.

Allergy to tree nuts represents an acute health problem. Sensitized people can be inadvertently exposed to hidden allergens resulting from cross-contamination of foods. For this reason, reliable and highly sensitive analytical methods are needed to be developed for control and labeling of food ingredients and products. In the present paper we have proposed a new allergen specific sandwich-ELISA for hazelnut operated in optical and electrochemical modes. The ELISA was based on chicken egg yolk antibodies raised against a major hazelnut allergen, Cor a 9. The developed ELISA has a limit of detection in phosphate buffer of 4 ng mL(-1). No significant cross-reactivity with peanut, wheat or other food ingredients has been detected. Extracts of blank control cookies did not show any false positive response and the limit of detection in cookies was estimated to be 0.1 µg of hazelnut protein per g of food (0.1 ppm). The ELISA protocol was successfully adapted to operate in electrochemical mode and it was applied for the detection of hazelnut traces in cookies.

Improvement of direct bioelectrocatalysis by cellobiose dehydrogenase on screen printed graphite electrodes using polyaniline modification.

Modification of graphite based screen printed electrodes (SPEs) by electrosynthesised polyaniline (PANI) has been applied to improve the electron exchange between cellobiose dehydrogenase (CDH, EC 1.1.99.18) from the ascomycete Myriococcum thermophilum and the surface of the SPE. The redox intermediate layer of the conducting polymer promotes the bioelectrocatalysis providing a higher current for lactose oxidation at a lower potential compared to CDH immobilised on a plain SPE. The current of the SPE|PANI|CDH electrode was more than 5 times higher as compared to that of a SPE|CDH electrode at a potential of 0 mV vs. Ag|AgCl. When comparing the response obtained through direct electron transfer with that obtained through mediated electron transfer, it was clearly observed that the improved current of the SPE|PANI|CDH electrode is due to the specific role of PANI, rather than caused by a rise of enzyme loading. The operational stability of the enzyme electrode based on PANI modified SPE was 5 times higher compared with that based on plain SPE.

Label-free detection of DNA hybridization at a liquid|liquid interface.

A novel electrochemical approach for label-free detection of DNA primary sequence has been proposed. The flow of nonelectroactive ions across a liquid|liquid interface was used as an electrochemical probe for detection of DNA hybridization. Disposable graphite screen-printed electrodes shielded with a thin layer of inert polymer plasticized with water-immiscible polar organic solvent were modified by probe oligonucleotide and used as a DNA sensor. The specific DNA coupling has been detected with impedance spectroscopy by decrease of ion-transfer resistance. The detection limit was of 10-8 M of target oligonucleotide. The reported sensor was suitable for discrimination of a single mismatch oligonucleotide from the full complementary one. The reported DNA sensor was advantageous over known physicochemical approaches, providing the most significant changes in the measured parameters.