Polymer Gel Substrate: Synthesis and Application in the Intensive Light Artificial Culture of Agricultural Plants

This work is devoted to the description of the synthesis of hydrogels in the process of cryotropic gel formation based on copolymerization of synthesized potassium 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate (SPMA-co-HEMA) and assessing the potential possibility of their use as substrates for growing plants in intensive light culture in a greenhouse. Gel substrates based on the SPMA-co-HEMA were created in two compositions, differing from each other in the presence of macro- and microelements, and their effects were studied on the plants' physiological state (content of chlorophylls a and b, activity of catalase and peroxidase enzymes, intensity of lipid peroxidation, elemental compositions) at the vegetative period of their development and on the plants' growth, productivity and quality of plant production at the final stages of development. Experiments were carried out under controlled microclimate conditions. Modern and standard generally accepted methods of gels were employed (ATR-FTIR and 13C NMR spectral studies, scanning electron microscopy, measurement of specific surface area and pore volume), as well as the methods of the physiological and chemical analysis of plants. The study demonstrated the swelling ability of the created gel substrates. Hydrogels' structure, their specific surface area, porosity, and pore volume were investigated. Using the example of representatives of leaf, fruit and root vegetable crops, the high biological activity of gel substrates was revealed throughout the vegetation period. Species specificity in the reaction of plants to the presence of gel substrates in the root-inhabited environment was revealed. Lettuce, tomato and cucumber plants were more responsive to the effect of the gel substrate, and radish plants were less responsive. At the same time, more pronounced positive changes in plant growth, quality and productivity were observed in cucumber and lettuce in the variant of gel substrates with macro- and microelements and in tomato plants in both variants of gel substrates. Further research into the mechanisms of the influence of gel substrates on plants, as well as the synthesis of new gel substrates with more pronounced properties to sorb and retain moisture is promising.

Synthesis, Photo- and Electroluminescence of New Polyfluorene Copolymers Containing Dicyanostilbene and 9,10-Dicyanophenanthrene in the Main Chain

Using palladium-catalyzed Suzuki polycondensation, we synthesized new light-emitting fluorene copolymers containing the dicyano derivatives of stilbene and phenanthrene and characterized them by gel permeation chromatography, UV-vis absorption spectroscopy, spectrofluorimetry, and cyclic voltammetry. The photoluminescence spectra of the synthesized polymers show significant energy transfer from the fluorene segments to the dicyanostilbene and 9,10-dicyanophenanthrene units, which is in agreement with the data of theoretical calculations. OLEDs based on these polymers were fabricated with an ITO/PEDOT-PSS (35 nm)/p-TPD (30 nm)/PVK (5 nm)/light emitting layer (70-75 nm)/PF-PO (20 nm)/LiF (1 nm)/Al (80 nm) configuration. Examination of their electroluminescence revealed that copolymers of fluorene with dicyanostilbene show yellow-green luminescence, while polymers with 9,10-dicyanophenanthrene have a greenish-blue emission. The 9,10-dicyanophenanthrene units have a more rigid structure compared to dicyanostilbene and, in OLEDs based on them, an increase in maximum brightness is observed with an increase in the content of the additive to the polymer chain. In particular, the device using fluorene copolymer with 9,10-dicyanophenanthrene (2.5 mol%) exhibited a maximum brightness of 9230 cd/m2 and a maximum current efficiency of 3.33 cd/A.

Biocomposite films based on chitosan and cerium oxide nanoparticles with promising regenerative potential

Polymeric nanocomposite materials have great potential in the development of tissue-engineered scaffolds because they affect the structure and properties of polymeric materials and regulate cell proliferation and differentiation. In this work, cerium oxide nanoparticles (CeONPs) were incorporated into a chitosan (CS) film to improve the proliferation of multipotent mesenchymal stem cells (MSCs). The citrate-stabilized CeONPs with a negative ζ-potential (-25.0 mV) were precoated with CS to obtain positively charged particles (+20.3 mV) and to prevent their aggregation in the composite solution. The composite CS-CeONP films were prepared in the salt and basic forms using a dry-cast process. The films obtained in both forms were characterized by a uniform distribution of CeONPs. The incorporation of CeONPs into the salt form of CS increased the stiffness of the CS-CeONP film, while the subsequent conversion of the film to the basic form resulted in a decrease in both the Young's modulus and the yield stress. The redox activity (Ce⁴⁺ ⇌ Ce³⁺) of cerium oxide in the CS-CeONP film was confirmed by thermal oxidative degradation. In vitro culture of MSCs showed that the CS-CeONP film has good biocompatibility, and in vivo experiments demonstrated its substantial regenerative potential.

Agricultural Applications of Superabsorbent Polymer Hydrogels

This review presents data from the past five years on the use of polymeric superabsorbent hydrogels in agriculture as water and nutrient storage and retention materials, as well as additives that improve soil properties. The use of synthetic and natural polymeric hydrogels for these purposes is considered. Although natural polymers, such as various polysaccharides, have undoubted advantages related to their biocompatibility, biodegradability, and low cost, they are inferior to synthetic polymers in terms of water absorption and water retention properties. In this regard, the most promising are semi-synthetic polymeric superabsorbents based on natural polymers modified with additives or grafted chains of synthetic polymers, which can combine the advantages of natural and synthetic polymeric hydrogels without their disadvantages. Such semi-synthetic polymers are of great interest for agricultural applications, especially in dry regions, also because they can be used to create systems for the slow release of nutrients into the soil, which are necessary to increase crop yields using environmentally friendly technologies.

New copolyhydrazides with anthrazoline fragments in the main chain: synthesis and optical properties

Several new 2,8-diphenylpyrido[3,2-g]quinoline-4,6-dicarbohydrazides were synthesized and copolyhydrazides based on them were obtained. Molecular weight, thermal, stress-strain and optical properties were investigated. It was shown that all polymer films exhibit significant luminescence in the 450-650 nm region, the profile and intensity of which depended on the nature and position of substituents in the phenylene fragment.

Poly(methacrylic Acid)-Cellulose Brushes as Anticancer Porphyrazine Carrier

The prospective strategy for treatment of cancer is based on the application of nano-sized macromolecular carriers, which are able penetrate inside and can be accumulated within tumor tissue. In this work graft copolymers of cellulose and poly(methacrylic acid) has been prepared and tested as a nanocontainers for the delivery of drug to tumor. For this purpose, two derivatives of porphyrazine suitable for photodynamic cancer therapy were loaded into prepared polymer brush. Fluorescence imaging was applied for monitoring of accumulation of porphyrazine in the CT26 murine colon carcinoma. The selective accumulation of cellulose brush loaded with porphyrazine in tumor was demonstrated by fluorescence intensity contrast between the tumor area and normal tissues. The tumor growth rate after photodynamic therapy were assessed and inhibition of its growth was revealed.

Bacterial Cellulose-Based Nanocomposites Containing Ceria and Their Use in the Process of Stem Cell Proliferation

A technique for the fabrication of bacterial cellulose-based films with CeO₂ nanofiller has been developed. The structural and morphological characteristics of the materials have been studied, their thermal and mechanical properties in dry and swollen states having been determined. The preparation methodology makes it possible to obtain composites with a uniform distribution of nanoparticles. The catalytic effect of ceria, regarding the thermal oxidative destruction of cellulose, has been confirmed by TGA and DTA methods. An increase in CeO₂ content led to an increase in the elastic modulus (a 1.27-fold increase caused by the introduction of 5 wt.% of the nanofiller into the polymer) and strength of the films. This effect is explained by the formation of additional links between polymer macro-chains via the nanoparticles’ surface. The materials fabricated were characterized by a limited ability to swell in water. Swelling caused a 20- to 30-fold reduction in the stiffness of the material, the mechanical properties of the films in a swollen state remaining germane to their practical use. The application of the composite films in cell engineering as substrates for the stem cells’ proliferation has been studied. The increase in CeO₂ content in the films enhanced the proliferative activity of embryonic mouse stem cells. The cells cultured on the scaffold containing 5 wt.% of ceria demonstrated increased cell survival and migration activity. An analysis of gene expression confirmed improved cultivation conditions on CeO₂-containing scaffolds.

CeO2 Nanoparticle-Containing Polymers for Biomedical Applications: A Review

The development of advanced composite biomaterials combining the versatility and biodegradability of polymers and the unique characteristics of metal oxide nanoparticles unveils new horizons in emerging biomedical applications, including tissue regeneration, drug delivery and gene therapy, theranostics and medical imaging. Nanocrystalline cerium(IV) oxide, or nanoceria, stands out from a crowd of other metal oxides as being a truly unique material, showing great potential in biomedicine due to its low systemic toxicity and numerous beneficial effects on living systems. The combination of nanoceria with new generations of biomedical polymers, such as PolyHEMA (poly(2-hydroxyethyl methacrylate)-based hydrogels, electrospun nanofibrous polycaprolactone or natural-based chitosan or cellulose, helps to expand the prospective area of applications by facilitating their bioavailability and averting potential negative effects. This review describes recent advances in biomedical polymeric material practices, highlights up-to-the-minute cerium oxide nanoparticle applications, as well as polymer-nanoceria composites, and aims to address the question: how can nanoceria enhance the biomedical potential of modern polymeric materials?

Polyimide-Based Nanocomposites with Binary CeO2/Nanocarbon Fillers: Conjointly Enhanced Thermal and Mechanical Properties

To design novel polymer materials with optimal properties relevant to industrial usage, it would seem logical to modify polymers with reportedly good functionality, such as polyimides (PIs). We have created a set of PI-based nanocomposites containing binary blends of CeO2 with carbon nanoparticles (nanocones/discs or nanofibres), to improve a number of functional characteristics of the PIs. The prime novelty of this study is in a search for a synergistic effect amidst the nanofiller moieties regarding the thermal and the mechanical properties of PIs. In this paper, we report on the structure, thermal, and mechanical characteristics of the PI-based nanocomposites with binary fillers. We have found that, with a certain composition, the functional performance of a material can be substantially improved. For example, a PI containing SO2-groups in its macrochains not only had its thermal stability enhanced (by ~20 °C, 10% weight loss up to 533 °C) but also had its stiffness increased by more than 10% (Young's modulus as high as 2.9-3.0 GPa) in comparison with the matrix PI. In the case of a PI with no sulfonic groups, binary fillers increased stiffness of the polymer above its glass transition temperature, thereby widening its working temperature range. The mechanisms of these phenomena are discussed. Thus, this study could contribute to the design of new composite materials with controllable and improved functionality.

Amphiphilic multicomponent molecular brushes

Multicomponent molecular brushes containing amphiphilic polymer moieties are promising objects of research of macromolecular chemistry. The development of stimulus-responsive systems sensitive to changes in environmental parameters, based on the molecular brushes, opens up new possibilities for their applications in medicine, biochemistry and microelectronics. The review presents the current understanding of the structures of main types of amphiphilic multicomponent brushes, depending on the chemical nature and type of coupling of the backbone and side chains. The approaches to the controlled synthesis of multicomponent molecular brushes of different architecture are analyzed. Self-assembly processes of multicomponent molecular brushes in selective solvents are considered.

The bibliography includes 259 references.

Synthesis and photoluminescence properties of co-polyamides with anthrazoline-containing units in the main chain

A series of anthrazoline-containing monomers are synthesized, and eight co-polyamides of different chemical structures, containing 1,9-anthrazoline fragments in the main chain, are obtained and investigated. Photoluminescent, stress-strain, and thermal properties of these polymers are studied. It is shown that polymers with fragments of 4,4'-(pyrido[3,2-g]-quinoline-2,8-diyl)dianiline and 4,4'-(10-methylpyrido[3,2-g]quinoline-2,8-diyl)dianiline possess an intense luminescence in the range 550-650 nm. The performed investigations made it possible to determine the effect of substituents of various natures in the anthrazoline cycle and the position of amide group (meta- and para-configurations) on optical, stress-strain, and thermal properties of copolymers, opening up a prospect for further developments of principles of design of polymers with optimal characteristics.

Effective delivery of porphyrazine photosensitizers to cancer cells by polymer brush nanocontainers

Efficient drug delivery can be assigned to tasks that attract the most acute attention of researchers in the field of anticancer drug design. We have reported the first case of using amphiphilic polymer brushes as nanocontainers for photosensitizer delivery to cancer cells. Regular graft-copolymers of hydrophobic polyimides with hydrophilic polymethacrylic acid side chains were loaded with photosensitive dye tetra(4-fluorophenyl)tetracyanoporphyrazine (Pz) providing a sufficiently stable homogeneous fraction of fluorescent Pz-loaded nanoparticles with a size of 100-150 nm. Pz-loaded polymer brushes were substantially more efficient for Pz delivery into cells compared with other types of particles examined, Pz-polyethyleneglycol and Pz-methylcellulose. In vivo, an efficient Pz delivery to tumor can also be expected since the Pz-PB particle size is in the optimal range for passive targeting. Pz-PB showed pronounced photodynamic activity, while, that is important, in the absence of irradiation the PB carrier itself was significantly less toxic than the dye itself. Summing up, water-soluble polymer brushes with polyimide backbones and polymethacrylic acid side chains can be regarded as a novel type of nanocontainers providing efficient intracellular drug delivery for photodynamic therapy of cancers.

Polymer biquinolyl-containing complexes of Pd(ii) as efficient catalysts for cyanation of aryl and vinyl halides with K4Fe(CN)6

Stereo- and chemoselective cyanation of compounds containing Csp²–Br bonds catalyzed by Pd–polymer complexes is reported.

New surface-enhanced Raman scattering platforms: composite calcium carbonate microspheres coated with astralen and silver nanoparticles

Surface-enhanced Raman scattering (SERS) microspectroscopy is a very promising label-free, noncontact, and nondestructive method for real-time monitoring of extracellular matrix (ECM) development and cell integration in scaffolds for tissue engineering. Here, we prepare a new type of micrometer-sized SERS substrate, core-shell microparticles composed of solid carbonate core coated with silver nanoparticles and polyhedral multishell fullerene-like structure, astralen. Astralen has been assembled with polyallylamine hydrochloride (PAH) by the layer-by-layer manner followed by Ag nanoparticle formation by means of a silver mirror reaction, giving the final structure of composite particles CaCO3(PAH/astralen)x/Ag, where x = 1-3. The components of the microparticle carry multiple functionalities: (i) an easy identification by Raman imaging (photostable astralen) and (ii) SERS due to a rough surface of Ag nanoparticles. A combination of Ag and astralen nanoparticles provides an enhancement of astralen Raman signal by more than 1 order of magnitude. Raman signals of commonly used scaffold components such as polylactide and polyvinyl alcohol as well as ECM component (hyaluronic acid) are significantly enhanced. Thus, we demonstrate that new mechanically robust and easily detectable (by astralen signal or optically) core-shell microspheres based on biocompatible CaCO3 can be used as SERS platform. Particle design opens many future perspectives for fabrication of SERS platforms with multiple functions for biomedical applications, for example, for theranostic.

DFT study of the effect of sigma-ligands on the structure of ester enolates in THF, as models of the active center in the anionic polymerization of methyl methacrylate

A Density Functional Theory (DFT) study was carried out on structures of the lithium ester enolate of methyl isobutyrate (MIB-Li) in THF solution, in the presence of TMEDA, dimethoxyethane (DME), crown ether 12-crown-4, and cryptand-2,1,1, as electron donor ligands (sigma-ligands). Both specific solvation with THF and/or ligand molecules and nonspecific solvation by the solvent continuum were taken into account. The possibility of ligand-separated ion pair formation was analyzed for each of the ligands, including THF alone. In most cases peripherally solvated dimers are the most stable species. Only in the presence of cryptand-2,1,1 was a ligand-separated triple ion pair, (MIB-Li-MIB)(-)(THF)(2),Li(2,1,1)(1)(+), shown to be comparable in stability to the THF-solvated dimer, (MIB-Li)(2)(THF)(4). These results are in agreement with experimental NMR data on the structure of MIB-Li in the presence of DME, 12-crown-4, and cryptand-2,1,1. An upfield shift of the (13)C NMR signal of the alpha-carbon of MIB-Li observed in the presence of cryptand-2,1,1, originally attributed to a ligand-separated monomer, MIB(-),Li(2,1,1)(+), was well reproduced by Hartree--Fock calculated NMR shifts for the predicted ligand-separated triple ion pair.