Chemical Sensors and Biosensors—Principles and Applications

Chemical and environmental engineering and biotechnology are among the fields now being transformed by continually increasing levels of automation. Whereas the objective in other sectors of industry is simply to increase efficiency, here considerations of system theory or safety demand a high level of automation. Either the processes are too complex and require multifunctional control with feedback, or an analysis of the safety requirements shows the necessity for a certain degree of redundancy in the safety measures, and for elimination of human error as a risk factor. With regard to quality control, cost-benefit analyses lead to striking conclusions which again indicate the need for highly automated, and above all reliable, systems to eliminate rejects. The crux of any automated system is the measurement and control technology; of central importance is the rapid, reliable, and in some cases continuous, measurement and interpretation of key processes or control variables. For this purpose a wide variety of recording instruments and sensors are used to give as accurate a picture as possible of the state of the system. It is obvious from this that the performance of the control system is critically dependent on the sensors. Errors in the measured quantities can become amplified in the control variables or, in dynamic systems, can lead to undesirable operating conditions. Moreover, as a consequence of great advances in microelectronics, “intelligent sensors” which can calibrate and control themselves will be one of the key technologies of the nineties. Unless fast and immediate information on the true current status of a system is available, microprocessors as control devices react blindly and unpredictably to errors in input information. New discoveries in the fields of electronic, electrochemical, and optical transducers are now being applied in heterogeneous catalysis and surface physics, and in biochemistry (enzymology and immunology); in these fields new chemical sensor principles are being tested, which could revolutionize instrumental methods of molecular analysis in particular, owing to their very favorable cost-performance relationship. This article aims to give an up-to-date overview of the current state of the art in these developments, with emphasis on their importance for analysis and their significance in relation to the chemist's interest in mechanisms for identifying substances.     

Umsetzungen von Ferrocenol und 1,1′-Ferrocendiol mit Cyclotriphosphazenen,P3N3F6 und P3N3Cl6

Reactions of Ferrocenol and 1,1′-Ferrocendiol with Cyclotriphosphazenes, P₃N₃F₆ and P₃N₃Cl₆ The hexahalogeno-cyclotriphosphazenes, P₃N₃X₆ (X ? F ( 1 a ), Cl ( 1 b )), react with ferrocenol (FcOH) in a molar ratio 1 : 1 to give the ferrocenoxy derivatives, FcO[P₃N₃X₅] (X ? F ( 3 a ), Cl ( 3 b )); in an analogous manner the tetrameric ring P₄N₄Cl₈ ( 2 b ) is converted to FcO[P₄N₄Cl₇] ( 4 b ).

1 Abkürzungen: Fc = Ferrocenyl, (C₅H₅)Fe(C₅H_4?); fc = 1,1′-ferrocendiyl, Fe(C₅H_4?)₂; rc = 1,1′-ruthenocendiyl, Ru(C₅H_4?)₂. Fluorphosphazene werden mit a , Chlorphosphazene mit b gekennzeichnet.

With 1,1′-ferrocenediol, (fc(OH) ₂ ), the cyclo triphosphazenes react in a molar ratio 1 : 1 to produce fcO ₂ [P ₃ N ₃ X ₄ ] (X ? F ( 5 a ), Cl ( 5 b )). According to the x-ray structure analysis, the 1,1′-ferrocenediolato group in 5 a , b is bound to two different phosphorus atoms. On the contrary, the 1,1′-ferrocenedithiolato- and 1,1′-ferrocenediselenolato units in fcS ₂ [P ₃ N ₃ X ₅ ] (X ? F ( 6 a ), Cl ( 6 b )) and fcSe ₂ [P ₃ N ₃ X ₅ ] (X ? F ( 7 a ), Cl ( 7 b )) are attached to only one phosphorus atom, and spirocyclic 1,3-dichalcogena-2-phospha-[3]ferrocenophanes are formed. All new products have been characterized on the basis of their ¹ H, ¹³ C and ³¹ P NMR as well as EI mass spectra. The molecular structures of 5 a , b and 6 a have been determined by x-ray structure analyses.     

In vitro anticancer activity of binuclear Ru(II) complexes with Schiff bases derived from 5-substituted salicylaldehyde and 2-aminopyridine with notably low IC50 values

The binuclear Ru(II) complexes with Schiff bases derived from 5-chlorosalicyladehyde and 2-aminopyridine and its 5-substituted salicylideneimine homologues were tested in vitro against cervical carcinoma (HeLa), metastatic colorectal adenocarcinoma (SW620), lung adenocarcinoma (A549), breast adenocarcinoma (MCF-7), and human lung fibroblast (WI-38) cell lines. All compounds showed strong antiproliferative activity with extremely low IC₅₀ values. The compounds expressed strong activity against gram-positive bacteria, Staphylococcus aureus and Enterococcus faecalis.     

Chiroptical detection during liquid chromatography,part 5: On-line measurement of circular dichroism spectra Δε(λ) during stops of chromatographic flow

Summary A procedure is described which serves to measure circular dichrograms () on line during stops of flow in liquid chromatography. Since the concentration of substrate in the spectrometer cell during the stop is not known, the differential absorption coefficients are calculated from the experimental differential absorbances A by means of UV absorption (i. e. photomultiplier voltage) data. Verifications of the procedure are obtained by its application to three substrates (Table 1), the () spectra of which were known. The present on-line technique is compared with a corresponding off-line method.The N,N-dimethylthiobenzamides1 and2 as well as the 9,10-phenanthrenequinone7 consist of interconvertible enantiomers because their planar states are destabilized by steric overcrowding of groups. The unknown dichrograms () of1, 2 and7 are obtained (Figs. 2 and 4) and discussed with reference to the helicities of these molecules.In memory of the late Professor Dr. Dr. h. c. Günther Snatzke.     

A Novel Anti-Inflammatory d-Peptide Inhibits Disease Phenotype Progression in an ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.     

Synthesis and Spectrophotometric Analysis of Microcapsules Containing Immortelle Essential Oil

In this study, microcapsules were prepared by solvent evaporation technique using ethyl cellulose component as wall and essential oil as core material. The synthesis of microcapsules was carried out using different oil masses. The analysis of the microcapsules was carried out using field emission scanning electron microscope (FE-SEM) and UV spectrophotometric analysis using absorption spectrophotometer. The obtained results confirm the regular spherical shape and size of the synthesized microcapsules. The qualitative and quantitative spectrophotometric analysis of the microencapsulated immortelle oil was measured at the wavelength of 265 nm. The calibration diagram was used to calculate the unknown concentrations of the microencapsulated oil. The obtained results confirm the application of the presented method as relevant for the possible determination of microencapsulated oil on textile materials.     

Mesoionic Carbene Cobalt Complexes as Multipurpose Catalyst Precursors for Hydrosilylation and Dihydropyrimidinone Synthesis

Metalation of CH₂OH-substituted triazolium salts with CoCl₂ under basic conditions affords C,O-bidentate chelating carbene Co(III) complexes ( 3a , 3b ), while analogous phenyl-substituted triazolium salts produce monodentate carbene Co(II) complexes ( 3c , 3d ). The distinct substituent-induced properties of the metal centers were demonstrated by electrochemical measurements and catalytic activities in two specific processes. The complexes showed appreciable activity in the reduction of C=O bonds through hydrosilylation, with methoxybenzene-functionalized triazolylidene Co(III) complex 3a achieving a high selectivity towards aldehydes vs. ketones with turnover frequencies (TOFs) up to 200 h⁻¹. The C,O-chelate systems were also active catalysts in the Biginelli process, a one-step three-component reaction for efficient dihydropyrimidinone synthesis. Optimization of reaction conditions provides high activity with complex 3a , reaching TOFs of 800 h⁻¹, the highest activity known for cobalt NHC complexes to date.     

Elucidating dynamic behavior of synthetic supramolecular polymers in water by hydrogen/deuterium exchange mass spectrometry

A comprehensive understanding of the structure, self-assembly mechanism, and dynamics of one-dimensional supramolecular polymers in water is essential for their application as biomaterials. Although a plethora of techniques are available to study the first two properties, there is a paucity in possibilities to study dynamic exchange of monomers between supramolecular polymers in solution. We recently introduced hydrogen/deuterium exchange mass spectrometry (HDX-MS) to characterize the dynamic nature of synthetic supramolecular polymers with only a minimal perturbation of the chemical structure. To further expand the application of this powerful technique some essential experimental aspects have been reaffirmed and the technique has been applied to a diverse library of assemblies. HDX-MS is widely applicable if there are exchangeable hydrogen atoms protected from direct contact with the solvent and if the monomer concentration is sufficiently high to ensure the presence of supramolecular polymers during dilution. In addition, we demonstrate that the kinetic behavior as probed by HDX-MS is influenced by the internal order within the supramolecular polymers and by the self-assembly mechanism.