Analytical Test Systems Research Articles

Microporous Block Copolymers Modified with Cu(II)-Coordinated Polyethylene Oxide-Substituted Silicas for Analytical Sensors.

The influence of stable-to-self-condensation Cu(II)-coordinated polyoxyethylene-substituted silicas (ASiP-Cu-0.5) on the synthesis of microporous block copolymers (OBCs) whose structural feature is the existence of coplanar polyisocyanate blocks of acetal nature (O-polyisocyanates) and a flexible-chain component of amphiphilic nature was studied. The use of ASiP-Cu-0.5 increased the yield of O-polyisocyanate blocks and the microphase separation of OBC. The resulting OBCs turned out to be effective sorbents for the analytical reagents PAN and PHENAZO, which, being in the micropore cavity, interacted with copper(II) and magnesium ions. To reduce the thickness of the selective OBC layer ten-fold and simplify the technology for obtaining analytical test systems, polyethylene terephthalate was used as a substrate for applying OBC. It was found that the increased sensitivity of the resulting test systems was due to the fact that in thin reaction layers, the efficiency of the formation of O-polyisocyanate blocks noticeably increased.

Silicas with Polyoxyethylene Branches for Modification of Membranes Based on Microporous Block Copolymers.

We have synthesized cubic and linear polysiloxanes containing polyoxyethylene branches (ASiP-Cu) using tetraethoxysilane, polyoxyethylene glycol, and copper chloride as precursors; the products are stable to self-condensation. The effect of copper chloride content on the chemical structure of ASiP-Cu has been established. A special study was aimed at defining the modifying effect of ASiP-Cu on the sorption characteristics of membranes based on microporous, optically transparent block copolymers (OBCs). These OBCs were produced using 2,4-toluene diisocyanate and block copolymers of ethylene and propylene oxides. The study demonstrated significantly increased sorption capacity of the modified polymers. On the basis of the modified microporous block copolymers and 1-(2-pyridylazo)-2-naphthol (PAN) analytical reagent, an analytical test system has been developed. Additionally, the modified OBCs have the benefit of high diffusion permeability for molecules of organic dyes and metal ions. It has been shown that the volume of voids and structural features of their internal cavities contribute to the complex formation reaction involving PAN and copper chloride.

Membrane analytical test system for highly sensitive determination of Hg2+ ions in natural waters

Abstract. A membrane test system has been developed for sensitive and specific detection of Hg2+ ions in natural waters. The test system uses gold nanoparticles synthesized by citrate reduction and a nitrocellulose membrane with a band of the conjugate of mercaptosuccinic acid (MSA) and bovine serum albumin (BSA). In the presence of Hg2+ ions, they are reduced by citrate and adsorbed on the surface of gold nanoparticles. The resulting product moves along the membrane of the test strip under the action of capillary forces and specifically binds to the MSA-BSA conjugate with the formation of a visually detectable colored band. The analysis takes 20 minutes without requiring additional manipulations or instrumentation. Under optimized conditions, the detection limit for Hg2+ ions was 0.13 ng/mL. The efficiency of the proposed approach was confirmed by its approbation for the control of natural waters; Hg2+ recovery ranged from 70 to 120%.

Personalising cancer medicine with prognostic markers.

Personalising cancer medicine with prognostic markers.

The possibility of molecular genetic identity testing of an unidentified body from the second world war

Background: In the current forensic scenario, molecular genetic analyzes are used to identify the remains of victims of natural and man-made disasters, emergencies, and war conflicts. Aim: This study aimed to summarize forensic molecular genetic examinations conducted at the RCFME for identifying the victims of the Second World War in the Russian Federation. This was conducted to assess the prospects of using DNA identification analysis for unidentified remains of bodies buried in 19391945. Material and methods: We studied 30 expert reports from 2007 to 2021 of 171 skeletal bodies from exhumed graves. The total number of objects studied was 421 (bone fragments and teeth, from 1 to 5 objects from 1 body). Results: Using the remains, genotypes of 167 people were established. The success rate of evidence-based molecular genetic identification was 98% (171 cases). Of these, positive identification was noted for 10 body remains and negative identification for 157 remains. Four skeletal bodies (2%) were deemed unsuitable for research. In most cases, indirect identification schemes were used a comparative study with putative relatives by biostatistical analysis of allelic variants of polymorphic loci of autosomal DNA as well as by direct comparative analysis of the polymorphism at the Y-chromosome DNA and mitochondrial DNA. Conclusions: Molecular genetic studies are highly effective for identifying the remains of victims of natural and man-made disasters, military conflicts, and other emergencies. The success of molecular genetic studies regarding the identification of victims of the Second World War conducted at the RCFME clearly demonstrate these possibilities. Simultaneously, it should be emphasized that this type of expertise falls to the category of rather complex molecular genetic studies, which requires the use of expanded panels of analytical test systems as well as the use of special methodological techniques and hardware and software.

Thiamine Assays—Advances, Challenges, and Caveats

Thiamine (vitamin B1) is essential to the health of all living organisms and deficiency has long been associated with diseases in animals such as fish, birds, alligators, and domesticated ruminant mammals. Thiamine is also implicated in several human diseases including Alzheimer's, diabetes, dementia, depression and, most notably, Wernicke–Korsakoff syndrome and Beriberi disease. Yet, highly sensitive and specific detection of thiamine remains an analytical challenge, as pM to nm levels of thiamine need to be detected in environmental and human samples, respectively, various phosphorylated variants need to be discriminated, and rapid on‐site detection would be highly desirable. Furthermore, appropriate sample preparation is mandatory, owing to the complexity of the relevant sample matrices including fish tissues, ocean water, and body fluids. This Review has two objectives. First, it provides a thorough overview of analytical techniques published for thiamine detection over the last 15 years. Second, it describes the principles of analytical approaches that are based on biorecognition and may open up new avenues for rapid and high‐throughput thiamine analysis. Most notably, periplasmic binding proteins, ribozymes, and aptamers are of particular interest, as they function as bioaffinity recognition elements that can fill an important assay technology gap, owing to the unavailability of thiamine‐specific commercial antibodies. Finally, the authors provide brief evaluations of key outcomes of the major assay concepts and suggest how innovative techniques could help develop sensitive and specific thiamine analytical test systems.

Development of an Automated LIBS Analytical Test System Integrated with Component Control and Spectrum Analysis Capabilities**supported by the National Major Scientific Instruments and Equipment Development Special Funds of China (No. 2011YQ030113)

The present paper proposes an automated Laser-Induced Breakdown Spectroscopy (LIBS) analytical test system, which consists of a LIBS measurement and control platform based on a modular design concept, and a LIBS qualitative spectrum analysis software and is developed in C#. The platform provides flexible interfacing and automated control; it is compatible with different manufacturer component models and is constructed in modularized form for easy expandability. During peak identification, a more robust peak identification method with improved stability in peak identification has been achieved by applying additional smoothing on the slope obtained by calculation before peak identification. For the purpose of element identification, an improved main lines analysis method, which detects all elements on the spectral peak to avoid omission of certain elements without strong spectral lines, is applied to element identification in the tested LIBS samples. This method also increases the identification speed. In this paper, actual applications have been carried out. According to tests, the analytical test system is compatible with components of various models made by different manufacturers. It can automatically control components to get experimental data and conduct filtering, peak identification and qualitative analysis, etc. on spectral data.

High-Performance Binary Protein Interaction Screening in a Microfluidic Format

The standard procedure to increase microfluidic chip performance is to grow the number of parallel test systems on the chip. This process is accompanied by miniaturizing biochemical workflows and micromechanical elements, which is often a major challenge for both engineering fields. In this work, we show that it is possible to substantially increase the runtime performance of a microfluidic affinity assay for protein interactions by simultaneously engineering fluid logics and assay chemistry. For this, synergistic effects between the micro- and chemical architecture of the chip are exploited. The presented strategy of reducing the runtime rather than size and volume of the mechanical elements and biological reagent compartments will, in general, be of importance for future analytical test systems on microfluidic chips to overcome performance barriers.

Development of Karl Fischer titration method using quality by design concept

Modern trends in drug quality control are moving toward incorporating quality into the method during its development. That course is in accordance with Quality by Design (QbD) concept defined by ICH Q 8 (R2) guideline. This implies that the method development begins by defining the method goals and collecting the relevant data, i.e. analyzing the properties of a given active pharmaceutical ingredient and evaluating the optimal experimental conditions. It is followed by a risk assessment defined by systematic robustness testing with the application of experimental design, while the final confirmation of the method reliability is done through the complete validation tests. In this paper, development of Karl Fischer titration for water determination in active pharmaceutical substance clindamycin phosphate is presented. Karl Fischer titration (KFT) is a widely used method in the pharmaceutical industry for determination of water content. For the analyzed substance, the European Pharmacopoeia suggests a relatively large amount of samples for the determination of water, so the objective of this study is to confirm the applicability of the developed method for the determination of water in small amount of samples applying QbD approach. According to QbD rules, detail development of coulometric Karl Fischer titration for water determination in clindamycin phosphate was done. For robustness testing fractional factorial design 24-1 was successful applied and confirmed that method was robust. Robustness was evaluated using statistical and graphical methods. Also, design space was defined so the region, in which factors could be changed without significant changes in water content, was defined. At the end, other validation parameters were determined and it was proved that analytical test system was capable of providing useful and valid analytical data.

Achieving energy conservation in Poisson–Boltzmann molecular dynamics: Accuracy and precision with finite-difference algorithms

Violation of energy conservation in Poisson–Boltzmann molecular dynamics, due to the limited accuracy and precision of numerical methods, is a major bottleneck preventing its wide adoption in biomolecular simulations. We explored the ideas of enforcing interface conditions by the immerse interface method and of removing charge singularity to improve the finite-difference methods. Our analysis of these ideas on an analytical test system shows significant improvement in both energies and forces. Our analysis further indicates the need for more accurate force calculation, especially the boundary force calculation.

Noncompetitive activation of peroxidase oxidation of o-phenylenediamine by melamine

Peroxidase-catalyzed oxidation of o-phenylenediamine (PDA) is greatly activated with melamine (MA) in 15 mM phosphate-citrate buffer at pH 6.0-7.4 in a noncompetitive manner: kcat and Km increase in direct proportion to the MA concentration. An extent of the activation is quantitatively characterized with a coefficient alpha (in M-1), which essentially increases along with the rise in pH from 6.0 to 7.4. MA acts as a nucleophilic catalyst in the oxidation process: it most likely affects the peroxidase active site from the distal position of heme. MA non-competitively inhibits the peroxidase oxidation of PDA at pH 4.3, since it completely loses its nucleophilic properties in acidic medium. A rapid, highly accurate, and simple analytical test system based on the kinetics of melamine-activated oxidation of PDA is proposed for the quantitative determination of melamine within the concentration range of 10(-4)-10(-3) M. This test system uses the spectrophotometric determination of the PDA oxidation product at 455 nm.