Determination of the action type of hydrate formation inhibitors by their infrared spectra

In this paper, differences of infrared spectra of hydrate formation inhibitors of thermodynamic and kinetic action types were investigated. The method was proposed for determining the action type of a hydrate formation inhibitor by its infrared spectrum. The relevance of the proposed method is due to its expressiveness in comparison with the testing of inhibitors in laboratory tests. It is proposed to use the method of Fourier transform infrared spectrometry. The method allows us to obtain data on the molecular and intermolecular interactions of the substance under study. The spectra obtained in the mode of attenuated total reflection were analyzed by the principal component analysis and the regression method of projection on latent structures, which are related to chemometric methods of analysis and make it possible to identify the key features of the inhibitor compositions that affect the mechanism of their action. The separation of the sample of infrared spectra of the studied inhibitors into two subgroups, which represent two different types of inhibitor action, was obtained. The principal component analysis makes it possible to identify the key features of the compositions of reagents that affect the mechanism of their action. For kinetic inhibitors, a characteristic ratio of the amplitudes of vibrations of the –OH and N–H functional groups in the internal standard of the spectrum was revealed. It is shown that the decisive factor in the division of inhibitors into groups is the difference between the resonant vibration frequencies corresponding to the valence vibrations of C–O, C–N bonds and the resonant vibration frequencies of organofluorine compounds. At the same time, the similarity in the amplitude of the indicated spectral regions was noted. For the group of thermodynamic inhibitors, the most influential bands in the IR spectrum were the bands of symmetric and asymmetric stretching vibrations of the C–H bonds in the CH2 and CH3 groups. There was a significant increase in the amplitude in the spectral range of 2950–2750 cm–1 compared with the signal amplitude in the regions of 3300–3400 cm–1 and 1200–1100 cm–1, also found in the spectra of this group of inhibitors. The method of projection on latent structures was used to develop a regression model to determine the mechanism of action of the studied inhibitors. The proposed method allows for express determination of the action type of hydrate formation inhibitors. Results could be used in oilfield chemistry to determine the action type of hydrate formation inhibitors used to prevent the formation of gas hydrates during the production, preparation or transportation of hydrocarbons

Sorption Properties of Clay and Pectin-Containing Hydrogels

As is known, polymeric polyelectrolyte hydrogels are superabsorbents that are capable of absorbing moisture in amounts many times greater than their own mass. Numerous studies have shown that besides water absorption and retention, they can also be effectively used as sorbents to purify water from heavy metals. In many works, attempts are made to improve the sorption properties of polyelectrolyte hydrogels by creating polymer composites based on them. Organic/inorganic composite materials frequently exhibited desired hybrid performance superior to their individual components and cost-efficient characteristics. The composites derived from natural polysaccharides and inorganic clay minerals are of special interest by virtue of their unique commercial and environmental advantages, which means that the design and development of environmentally friendly superabsorbents, introducing natural ingredients, have long been necessary. In this paper, we consider polymer hydrogels based on a copolymer of acrylic acid and acrylamide filled with pectin and bentonite. The aim of this study is to investigate the influence of chemical conditions on hydrogels and their composites, kinetic, and absorption behavior toward metal ions in the presence of the chelating agent. In this chapter, an investigation of the kinetic patterns of swelling, deswelling, and sorption of the hydrogels and their composites will be presented

Синтез и функционализация нанокристаллов бактериальной целлюлозы из чайного гриба для раневых повязок

In this study, bacterial cellulose nanocrystals and aldehyde functionalized bacterial cellulose nanocrystals were synthesized from kombucha tea. Bacterial cellulose derived from kombucha tea is a biopolymer synthesized by a symbiotic consortium of bacteria and yeast (SCOBY). The main goal of this work was the synthesis and chemical modification of cellulose nanocrystals from bacterial cellulose isolated from kombucha tea. The hydrolysis of bacterial cellulose using sulfuric acid resulted in bacterial cellulose nanocrystals. Aldehyde modified bacterial cellulose nanocrystals were synthesized using periodate oxidation in order to acquire new properties such as a non-toxic crosslinking agent with other biopolymers. The bacterial cellulose nanocrystals and dialdehyde bacterial cellulose nanocrystals were characterized by FT-IR spectroscopy, X‑ray diffraction, thermal analysis and particle size distribution. The synthesized bacterial cellulose nanocrystals and the dialdehyde derivative are excellent materials that could be used as potent wound dressing materials and scaffolds for tissue engineering applicationsВ этом исследовании нанокристаллы бактериальной целлюлозы и нанокристаллы бактериальной целлюлозы, функционализированные альдегидными группами, были синтезированы из чайного гриба. Бактериальная целлюлоза, полученная из чайного гриба, представляет собой биополимер, синтезированный симбиотическим консорциумом бактерий и дрожжей (SCOBY). Основной целью данной работы был синтез и химическая модификация нанокристаллов целлюлозы из бактериальной целлюлозы, выделенной из чайного гриба. В результате гидролиза бактериальной целлюлозы серной кислотой были получены нанокристаллы бактериальной целлюлозы. Нанокристаллы бактериальной целлюлозы, модифицированные альдегидными группами, были синтезированы с использованием перийодата для приобретения новых свойств, таких как нетоксичный сшивающий агент с другими биополимерами. Нанокристаллы бактериальной целлюлозы и нанокристаллы диальдегидной бактериальной целлюлозы были охарактеризованы с помощью ИК-Фурье-спектроскопии, рентгеновской дифракции, термического анализа, и определены распределения частиц по размерам. Синтезированные нанокристаллы бактериальной целлюлозы и ее функционализированное альдегидными группами производное являются превосходными материалами, которые можно использовать в качестве эффективных перевязочных материалов для ран и каркасов для приложений тканевой инженери

The Influence of Oxidant on Gelatin–Tannin Hydrogel Properties and Structure for Potential Biomedical Application

Nowadays, there is a widespread usage of sodium periodate as an oxidant for synthesizing gelatin–tannin hydrogels. The impact of iodine compounds could have a harmful effect on human health. The study focuses on the proposal of alternative oxidizing systems for tannin oxidation. Gelatin–tannin hydrogels were obtained based on the usage of H2O2/DMSO/KMnO4/KIO4 oxidants and characterized with sorption, thermal (TGA, DTG, DSC), mechanical, FTIR and other methods. The sorption experiments were carried out in a phosphate buffer (pH = 5.8/7.4/9) and distilled water and were investigated with Fick’s law and pseudosecond order equation. The pH dependence of materials in acid media indicates the possibility of further usage as stimuli-responsive systems for drug delivery. Thermal transitions demonstrate the variation of structure with melting (306 ÷ 319 °C) and glass transition temperatures (261 ÷ 301 °C). The activation energy of water evaporation was calculated by isoconversional methods (Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa) ranging from 4 ÷ 18 to 14 ÷ 38 kJ/mole and model-fitting (Coats–Redfern, Kennedy–Clark) methods at 24.7 ÷ 45.3 kJ/mole, indicating the smooth growth of values with extent of conversion. The network parameters of the hydrogels were established by modified Flory–Rehner and rubber elasticity theories, which demonstrated differences in values (5.96 ÷ 21.27·10−3 mol/cm3), suggesting the limitations of theories. The sorption capacity, tensile strength and permeability for water/oxygen indicate that these materials may find their application in field of biomaterials

The Scope and Limitations of In Vivo and In Silico Models of Cardiac Amyloidosis

Amyloidosis is a systemic disease, leading to the disfunction of many organs. There are several clinical and morphological forms of amyloidosis based on the organ-specific nature of amyloid fibril deposition, which is found in the heart, brain, kidneys, spleen, liver, pancreas, thyroid glands, bone marrow and intestines. The nature of organ damage correlates with the types of amyloid fibrils. Thus, damage to the tissues of the heart and kidneys are the most significant factors affecting mortality. The complexity of drug molecule discovery against amyloidosis is connected with the fact that more than 30 proteins are involved in fibril formation. The fact that only two small molecules, namely diflunisal and tafamidis, are clinically used nowadays underlines the complexity in this field of research. The mechanism of action for both drugs include the stabilization of the tetrameric form of transthyretin. The crucial approach for the discovery of drug molecules against cardiac amyloidosis requires the use of predictive models. The main restrictions of most developed in vivo models, however, are related to their reproducibility and cost. Therefore, an in silico approach may be a relatively effective procedure to minimize time and difficulty during the drug discovery process. In this paper, we collected key information which highlights the scope and limitations of the development of an in silico approach

Bilayer Hydrogels for Wound Dressing and Tissue Engineering

A large number of different skin diseases such as hits, acute, and chronic wounds dictate the search for alternative and effective treatment options. The wound healing process requires a complex approach, the key step of which is the choice of a dressing with controlled properties. Hydrogel-based scaffolds can serve as a unique class of wound dressings. Presented on the commercial market, hydrogel wound dressings are not found among proposals for specific cases and have a number of disadvantages—toxicity, allergenicity, and mechanical instability. Bilayer dressings are attracting great attention, which can be combined with multifunctional properties, high criteria for an ideal wound dressing (antimicrobial properties, adhesion and hemostasis, anti-inflammatory and antioxidant effects), drug delivery, self-healing, stimulus manifestation, and conductivity, depending on the preparation and purpose. In addition, advances in stem cell biology and biomaterials have enabled the design of hydrogel materials for skin tissue engineering. To improve the heterogeneity of the cell environment, it is possible to use two-layer functional gradient hydrogels. This review summarizes the methods and application advantages of bilayer dressings in wound treatment and skin tissue regeneration. Bilayered hydrogels based on natural as well as synthetic polymers are presented. The results of the in vitro and in vivo experiments and drug release are also discussed

Hyaluronan-Based Nanofibers: Fabrication, Characterization and Application

Nano- and microfibers based on biopolymers are some of the most attractive issues of biotechnology due to their unique properties and effectiveness. Hyaluronan is well-known as a biodegradable, naturally-occurring polymer, which has great potential for being utilized in a fibrous form. The obtaining of fibers from hyaluronan presents a major challenge because of the hydrophilic character of the polymer and the high viscosity level of its solutions. Electrospinning, as the advanced and effective method of the fiber generation, is difficult. The nano- and microfibers from hyaluronan may be obtained by utilizing special techniques, including binary/ternary solvent systems and several polymers described as modifying (or carrying), such as polyethylene oxide (PEO) and polyvinyl alcohol (PVA). This paper reviews various methods for the synthesis of hyaluronan-based fibers, and also collects brief information on the properties and biological activity of hyaluronan and fibrous materials based on it

FTIR Spectroscopy Study of the Secondary Structure Changes in Human Serum Albumin and Trypsin under Neutral Salts

The effect of neutral salts on protein conformation was first analyzed by Hofmeister in 1888, however, even today this phenomenon is not completely understood. To clarify this effect, we studied changes in the secondary structure of two proteins: human serum albumin with predominantly α-helical structure and porcine pancreas β-trypsin with the typical β-structural arrangement in aqueous solutions of neutral salts (KSCN, KCl, (NH4)2SO4). The changes in the secondary structure were studied at 23 °C and 80 °C by using the second derivative deconvolution method of the IR spectra. Our results demonstrated that the ability of the salts to stabilize/destabilize these two proteins correlates with the Hofmeister series of ions. At the same time, some exceptions were also observed. The destabilization of the native structures of both α-helical albumin and β-structural trypsin upon interaction with neutral salts leads to the formation of intermolecular β-sheets typical for amyloid fibrils or amorphous aggregates. Thus, our quantitative FTIR-spectroscopy analysis allowed us to further clarify the mechanisms and complexity of the neutral salt actions on protein structures which may lead to strategies preventing unwelcome misfolding of proteins

Diflunisal Targeted Delivery Systems: A Review

Diflunisal is a well-known drug for the treatment of rheumatoid arthritis, osteoarthritis, primary dysmenorrhea, and colon cancer. This molecule belongs to the group of nonsteroidal anti-inflammatory drugs (NSAID) and thus possesses serious side effects such as cardiovascular diseases risk development, renal injury, and hepatic reactions. The last clinical data demonstrated that diflunisal is one of the recognized drugs for the treatment of cardiac amyloidosis and possesses a survival benefit similar to that of clinically approved tafamidis. Diflunisal stabilizes the transthyretin (TTR) tetramer and prevents the misfolding of monomers and dimers from forming amyloid deposits in the heart. To avoid serious side effects of diflunisal, the various delivery systems have been developed. In the present review, attention is given to the recent development of diflunisal-loaded delivery systems, its technology, release profiles, and effectiveness

Influence of Thermal Treatment and Acetic Acid Concentration on the Electroactive Properties of Chitosan/PVA-Based Micro- and Nanofibers

This study presents, for the first time, a comprehensive investigation of the influence of pre- and post-fabrication parameters for the electroactive properties of electrospun chitosan/PVA-based micro- and nanofibers. Chitosan/PVA fibers were fabricated using electrospinning, characterized, and tested as electroactive materials. Solutions with different acetic acid contents (50, 60, 70, and 80 v/v%) were used, and the rheological properties of the solutions were analyzed. Characterization techniques, such as rheology, conductivity, optical microscopy, a thermogravimetric analysis, differential scanning calorimetry, a tensile test, and FT-IR spectroscopy, were utilized. Fiber mats from the various solutions were thermally treated, and their electroactive behavior was examined under a constant electric potential (10 V) at different pHs (2–13). The results showed that fibers electrospun from 80% acetic acid had a lower electroactive response and dissolved quickly. However, thermal treatment improved the stability and electroactive response of all fiber samples, particularly the ones spun with 80% acetic acid, which exhibited a significant increase in speed displacement from 0 cm−1 (non-thermally treated) to 1.372 cm−1 (thermally treated) at a pH of 3. This study sheds light on the influence of pre- and post-fabrication parameters on the electroactive properties of chitosan/PVA fibers, offering valuable insights for the development of electroactive materials in various applications