At-line bioprocess monitoring by immunoassay with rotationally controlled serial siphoning and integrated supercritical angle fluorescence optics

In this paper we report a centrifugal microfluidic “lab-on-a-disc” system for at-line monitoring of human immunoglobulin G (hIgG) in a typical bioprocess environment. The novelty of this device is the combination of a heterogeneous sandwich immunoassay on a serial siphon-enabled microfluidic disc with automated sequential reagent delivery and surface-confined supercritical angle fluorescence (SAF)-based detection. The device, which is compact, easy-to-use and inexpensive, enables rapid detection of hIgG from a bioprocess sample. This was achieved with, an injection moulded SAF lens that was functionalized with aminopropyltriethoxysilane (APTES) using plasma enhanced chemical vapour deposition (PECVD) for the immobilization of protein A, and a hybrid integration with a microfluidic disc substrate. Advanced flow control, including the time-sequenced release of on-board liquid reagents, was implemented by serial siphoning with ancillary capillary stops. The concentration of surfactant in each assay reagent was optimized to ensure proper functioning of the siphon-based flow control. The entire automated microfluidic assay process is completed in less than 30 min. The developed prototype system was used to accurately measure industrial bioprocess samples that contained 10 mg mL⁻¹ of hIgG.     

Substitution pattern and stereochemistry versus liquid crystalline behaviour [1]

Abstract

Selectively O-alkylated inositols of myo-, scyllo- and chiro-configuration allow detailed studies of the relationship between the substitution pattern in the cyclohexane ring and the liquid crystalline properties observed to be made for these mainly novel cyclic compounds containing hydroxyl functions. The types of thermotropic mesophase formed and containing hydrogen bonds are strongly influenced by the number and the stereochemical arrangement of both the hydroxyl groups and the alkyloxy chains, as well as by their positions on the cyclohexane ring.

The mesophases of the various new inositol ethers have been studied by polarizing optical microscopy and differential scanning calorimetry, and are discussed here in comparison with known systems, as a function of the above mentioned structural factors.     

Dielectric studies of two liquid crystalline benzoates with coupled and decoupled CN groups

The results of dielectric studies performed in a broad frequency range for two compounds, 4-cyanophenyl 4-n-heptylbenzoate (7BBCN) and 4-(4-cyanobutyloxy)phenyl 4- n-heptylbenzoate (7BB4CN), are compared. They have the same molecular core whereas the strongly polar CN group is attached to the benzene ring in 7BBCN or is separated from it by the butyloxy chain in 7BB4CN. 7BBCN has a nematic phase, whereas 7BB4CN exhibits a monotropic nematic and smectic A₂ polymorphism. Large differences in the dielectric properties of the two substances were found. The analysis of the results led to the conclusion that the antiparallel dipole-dipole associations are considerably stronger in the substance with a decoupled CN group.     

A New Procedure for Highly Regio‐ and Stereoselective Iodoacetoxylation of Protected Glycals and α‐1,2‐Cyclopropanated Sugars

Protected glycals and α‐1,2‐cyclopropanated sugars were converted in high yields and selectivities in less than 2 h at low temperatures to 2‐deoxy‐2‐iodoglycosyl acetates or novel 2‐deoxy‐2‐iodomethylglycosyl acetates using the simple, inexpensive reagent mixture of ammonium iodide, hydrogen peroxide, and acetic anhydride/acetic acid in acetonitrile. The protected glycals gave rise to 2‐deoxy‐2‐bromoglycosyl acetates when ammonium bromide was used instead of the iodide, although longer reaction times were required and selectivities were inferior. Other simple olefins such as styrene and indene were also converted to their corresponding 1,2‐trans‐iodoacetates.     

Assembling a Phthalocyanine and Perylenediimide Donor–Acceptor Hybrid through a Platinum(II) Diacetylide Linker

In a novel electron‐donor–acceptor conjugate, phthalocyanine (Pc) and perylenediimide (PDI) are connected through a trans‐platinum(II) diacetylide linker to yield Pc‐Pt‐PDI 1 . In the ground state, the presence of Pt^II disrupts the electronic communication between the two electroactive components, as revealed by UV/Vis spectroscopy and electrochemical studies. The photophysical behavior of 1 is compared with that of the corresponding Pc‐PDI electron‐donor–acceptor conjugate 2 in terms of charge separation and charge recombination. The insertion of Pt^II between Pc and PDI impacts the results in a longer‐lived Pc ^{. +}/PDI ^{. ?} radical ion‐pair state. In addition, the intermediately formed Pc triplet excited state is formed with higher quantum yields in 1 than in 2 .     

A conformationally constrained fused tricyclic nisin AB-ring system mimic toward an improved pyrophosphate binder of lipid II

The bacteria-specific membrane component lipid II is essential for bacterial cell wall synthesis. A tricyclic nisin mimic was designed and synthesized in which both thioether moieties were mimicked by an alkane-bridge, as well as the introduction of a third conformational constraint consisting of a macrocyclic lactam-bridge between the N-terminus and the B-ring. The newly designed tricyclic AB-ring mimic was found to bind lipid II since it was able to inhibit nisin-induced membrane leakage in a dose-dependent manner. These results imply that the tricyclic AB-ring mimic may form a novel class of lead structures for the development of nisin-based peptide antibiotics.     

Evaluation of a commercial enzymatic test kit regarding the quantitative analysis of different free fatty acids

The quantitative determination of the total free fatty acids (FFAs) is an important analytical task because FFAs exhibit important physiological effects and are also relevant in many other fields, for instance, in food research. Our aim was to investigate whether a commercially available enzymatic test kit developed for the determination of FFAs in human serum is also suitable to determine different physiological and nonphysiological FFAs and to which extent the impact on the sensitivities (i.e., the accuracy by which a given FFA can be determined) differ. It will be shown that the chain length as well as the double bond content has a significant impact on the sensitivity by which a given FFA can be determined. For instance, palmitic acid (16:0) is determined with an approximately 20 times higher sensitivity in comparison to docosahexaenoic acid (22:6n-3). All data were obtained by measuring the concentrations of the FFAs by gas chromatography, and selected FFAs were also determined in a complex matrix of human serum. It is concluded that this kit is not useful if major alterations of the FFA composition of a complex mixture are expected because the individual FFAs are not detected with the same sensitivities: the concentrations of polyunsaturated FFA determined by this kit are wrong. Figure

The used enzymatic kit detects different free fatty acids with significantly different sensitivities: the number of carbon atoms and the number of double bonds massively contribute to these differences     

Optimal control for lithium-ion batteries

Modelling, simulation and optimal control for a lithium-ion battery cell is discussed. The model involves ionic concentrations, currents and potentials in the electrodes and the separator together with the battery temperature as state variables. The resulting system is a nonlinear PDAE system with 10 partial, 1 ordinary differential and 4 algebraic equations involving the Butler-Volmer kinetics for describing the interaction of ionic currents and potentials. Time-optimal charging of the battery subject to age-preventing leads to a state-constrained optimal control problem which is solved in two ways. A first-discretize-then-optimize approach leads to a high-dimensional nonlinear optimization problem which is solved by an efficient solver. As an alternative, a feedback control law along an active arc of the state constraint of order 1 is derived to formulate and solve the corresponding so-called induced optimization problem. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)