Chemical Modification of Nanocrystalline Cellulose for Manufacturing of Osteoconductive Composite Materials.

Cellulose is one of the main renewable polymers whose properties are very attractive in many fields, including biomedical applications. The modification of nanocrystalline cellulose (NCC) opens up the possibility of creating nanomaterials with properties of interest as well as combining them with other biomedical polymers. In this work, we proposed the covalent modification of NCC with amphiphilic polyanions such as modified heparin (Hep) and poly(αL-glutamic acid) (PGlu). The modification of NCC should overcome two drawbacks in the production of composite materials based on poly(ε-caprolactone) (PCL), namely, (1) to improve the distribution of modified NCC in the PCL matrix, and (2) to provide the composite material with osteoconductive properties. The obtained specimens of modified NCC were characterized by Fourier-transform infrared spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy, dynamic and electrophoretic light scattering, as well as thermogravimetric analysis. The morphology of PCL-based composites containing neat or modified NCC as filler was studied by optical and scanning electron microscopy. The mechanical properties of the obtained composites were examined in tensile tests. The homogeneity of filler distribution as well as the mechanical properties of the composites depended on the method of NCC modification and the amount of attached polyanion. In vitro biological evaluation showed improved adhesion of human fetal mesenchymal stem cells (FetMSCs) and human osteoblast-like cells (MG-63 osteosarcoma cell line) to PCL-based composites filled with NCC bearing Hep or PGlu derivatives compared to pure PCL. Furthermore, these composites demonstrated the osteoconductive properties in the experiment on the osteogenic differentiation of FetMSCs.

Precisely Printable Silk Fibroin/Carboxymethyl Cellulose/Alginate Bioink for 3D Printing.

Three-dimensional (3D) bioprinting opens up many possibilities for tissue engineering, thanks to its ability to create a three-dimensional environment for cells like an extracellular matrix. However, the use of natural polymers such as silk fibroin in 3D bioprinting faces obstacles such as having a limited printability due to the low viscosity of such solutions. This study addresses these gaps by developing highly viscous, stable, and biocompatible silk fibroin-based inks. The addition of 2% carboxymethyl cellulose sodium and 1% sodium alginate to an aqueous solution containing 2.5 to 5% silk fibroin significantly improves the printability, stability, and mechanical properties of the printed scaffolds. It has been demonstrated that the more silk fibroin there is in bioinks, the higher their printability. To stabilize silk fibroin scaffolds in an aqueous environment, the printed structures must be treated with methanol or ethanol, ensuring the transition from the silk fibroin's amorphous phase to beta sheets. The developed bioinks that are based on silk fibroin, alginate, and carboxymethyl cellulose demonstrate an ease of printing and a high printing quality, and have a sufficiently good biocompatibility with respect to mesenchymal stromal cells. The printed scaffolds have satisfactory mechanical characteristics. The resulting 3D-printing bioink composition can be used to create tissue-like structures.

Effect of Phytic Acid Addition on the Structure of Collagen-Hyaluronic Acid Composite Gel.

Composite collagen gels with hyaluronic acid are developed tissue-engineered structures for filling and regeneration of defects in various organs and tissues. For the first time, phytic acid was used to increase the stability and improve the mechanical properties of collagen gels with hyaluronic acid. Phytic acid is a promising cross-linker for collagen hydrogels and is a plant-derived antioxidant found in rich sources of beans, grains, and oilseeds. Phytic acid has several benefits due to its antioxidant, anticancer, and antitumor properties. In this work, studies were carried out on the kinetics of the self-assembly of collagen molecules in the presence of phytic and hyaluronic acids. It was shown that both of these acids do not lead to collagen self-assembly. Scanning electron microscopy showed that in the presence of phytic and hyaluronic acids, the collagen fibrils had a native structure, and the FTIR method confirmed the chemical cross-links between the collagen fibrils. DSC and rheological studies demonstrated that adding the phytic acid improved the stability and modulus of elasticity of the collagen gel. The presence of hyaluronic acid in the collagen gel slightly reduced the effect of phytic acid. The presence of phytic acid in the collagen gel improved the stability of the scaffold, but, after 1 week of cultivation, slightly reduced the viability of mesenchymal stromal cells cultured in the gel. The collagen type I gel with hyaluronic and phytic acids can be used to replace tissue defects, especially after the removal of cancerous tumors.

Structure and Properties of Composite Fibers Based on Chitosan and Single-Walled Carbon Nanotubes for Peripheral Nerve Regeneration.

This study focused on a potential application of electrically conductive, biocompatible, bioresorbable fibers for tubular conduits aimed at the regeneration of peripheral nerves. The conducting, mechanical, and biological properties of composite fibers based on chitosan and single-walled carbon nanotubes were investigated in this paper. It was shown that introducing 0.5 wt.% of SWCNT into the composite fibers facilitated the formation of a denser fiber structure, resulting in improved strength (σ = 260 MPa) and elastic (E = 14 GPa) characteristics. Additionally, the composite fibers were found to be biocompatible and did not cause significant inflammation or deformation during in vivo studies. A thin layer of connective tissue formed around the fiber.

Composites Based on Poly(ε-caprolactone) and Graphene Oxide Modified with Oligo/Poly(Glutamic Acid) as Biomaterials with Osteoconductive Properties.

The development of new biodegradable biomaterials with osteoconductive properties for bone tissue regeneration is one of the urgent tasks of modern medicine. In this study, we proposed the pathway for graphene oxide (GO) modification with oligo/poly(glutamic acid) (oligo/poly(Glu)) possessing osteoconductive properties. The modification was confirmed by a number of methods such as Fourier-transform infrared spectroscopy, quantitative amino acid HPLC analysis, thermogravimetric analysis, scanning electron microscopy, and dynamic and electrophoretic light scattering. Modified GO was used as a filler for poly(ε-caprolactone) (PCL) in the fabrication of composite films. The mechanical properties of the biocomposites were compared with those obtained for the PCL/GO composites. An 18-27% increase in elastic modulus was found for all composites containing modified GO. No significant cytotoxicity of the GO and its derivatives in human osteosarcoma cells (MG-63) was revealed. Moreover, the developed composites stimulated the proliferation of human mesenchymal stem cells (hMSCs) adhered to the surface of the films in comparison with unfilled PCL material. The osteoconductive properties of the PCL-based composites filled with GO modified with oligo/poly(Glu) were confirmed via alkaline phosphatase assay as well as calcein and alizarin red S staining after osteogenic differentiation of hMSC in vitro.

Covalent conjugates based on nanodiamonds with doxorubicin and a cytostatic drug from the group of 1,3,5-triazines: Synthesis, biocompatibility and biological activity.

We report the synthesis of covalent conjugates of nanodiamonds with doxorubicin and a cytostatic drug from the class of 1,3,5-triazines. The obtained conjugates were identified using a number of physicochemical methods (IR-spectroscopy, NMR-spectroscopy, XRD, XPS, TEM). As a result of our study, it was found that ND-СONH-Dox and ND-COO-Diox showed good hemocompatibility, since they did not affect plasma coagulation hemostasis, platelet functional activity, and erythrocyte membrane. The ND-COO-Diox conjugates are also capable of binding to human serum albumin due to the presence of ND in their composition. In the study of the cytotoxic properties of ND-СONH-Dox and ND-COO-Diox in the T98G glioblastoma cell line, indicating that ND-СONH-Dox and ND-COO-Diox demonstrate greater cytotoxicity at lower concentrations of Dox and Diox in the composition of the conjugates compared to individual drugs; the cytotoxic effect of ND-COO-Diox was statistically significantly higher than that of ND-СONH-Dox at all concentrations studied. Greater cytotoxicity at lower concentrations of Dox and Diox in the composition of conjugates compared to individual cytostatics makes it promising to further study the specific antitumor activity and acute toxicity of these conjugates in models of glioblastoma in vivo. Our results demonstrated that ND-СONH-Dox and ND-COO-Diox enter HeLa cells predominantly via a nonspecific actin-dependent mechanism, while for ND-СONH-Dox a clathrin-dependent endocytosis pathway. All data obtained provide that the synthesized nanomaterials show a potential application as the agents for intertumoral administration.

Surface Modification of Electrospun Bioresorbable and Biostable Scaffolds by Pulsed DC Magnetron Sputtering of Titanium for Gingival Tissue Regeneration.

In this study, polymer scaffolds were fabricated from biodegradable poly(lactide-co-glycolide) (PLGA) and from non-biodegradable vinylidene fluoride-tetrafluoroethylene (VDF-TeFE) by electrospinning. These polymer scaffolds were subsequently surface-modified by sputtering titanium targets in an argon atmosphere. Direct current pulsed magnetron sputtering was applied to prevent a significant influence of discharge plasma on the morphology and mechanical properties of the nonwoven polymer scaffolds. The scaffolds with initially hydrophobic properties show higher hydrophilicity and absorbing properties after surface modification with titanium. The surface modification by titanium significantly increases the cell adhesion of both the biodegradable and the non-biodegradable scaffolds. Immunocytochemistry investigations of human gingival fibroblast cells on the surface-modified scaffolds indicate that a PLGA scaffold exhibits higher cell adhesion than a VDF-TeFE scaffold.

Effect of Functionalization of the Polycaprolactone Film Surface on the Mechanical and Biological Properties of the Film Itself.

The lack of suitable functional groups for cell adhesion on the surface of Polycaprolactone (PCL) is one of the main limitations in order to use PCL for biomedical applications. The aim of this research is to modify the PCL film surface using arginine, via an aminolysis reaction. In this regard, after PCL films formation by casting method, they were immersed in arginine solutions of various concentration at room temperature or then heated to 40 °C and in the presence of isopropanol or without it. To assess the structure of the modified surface, its wettability, and mechanical properties, methods of measuring the contact angle and the strip tensile test were used, and to compare the degree of attachment and the rate of cell proliferation, the method of fluorescent staining of cultured cells was used. The change in protein synthesis by cells on the modified surface was assessed using Western blotting. The results obtained show that the treatment of PCL films with an aqueous solution of arginine at room temperature for 1 day increases the hydrophilicity of the surface. Wherein surface modification led to a two-fold decrease of mechanical strength and flow stress, but elongation increase by about 30% for PCL films after modification in 0.5 M aqueous arginine solution at room temperature. Moreover, cell attachment and proliferation, as well as collagen synthesis, were significantly enhanced after arginine modification. The proposed simple and effective method for modifying PCL films with arginine significantly expands the possibilities for developing biocompatible scaffolds for tissue engineering.

The Structural Interactions of Molecular and Fibrillar Collagen Type I with Fibronectin and Its Role in the Regulation of Mesenchymal Stem Cell Morphology and Functional Activity.

The observed differences in the structure of native tissue and tissue formed in vitro cause the loss of functional activity of cells cultured in vitro. The lack of fundamental knowledge about the protein mechanism interactions limits the ability to effectively create in vitro native tissue. Collagen is able to spontaneously assemble into fibrils in vitro, but in vivo, other proteins, for example fibronectin, have a noticeable effect on this process. The molecular or fibrillar structure of collagen plays an equally important role. Therefore, we studied the interaction of the molecular and fibrillar structure of collagen with fibronectin. Atomic force and transmission electron microscopy showed that the presence of fibronectin does not affect the native structure and diameter of collagen fibrils. Confocal microscopy demonstrated that the collagen structure affects the cell morphology. Cells are better spread on molecular collagen compared with cells cultured on fibrillar collagen. Fibronectin promotes the formation of a large number of focal contacts, while in combination with collagen of both forms, its effect is leveled. Thus, understanding the mechanisms of the relationship between the protein structure and composition will effectively manage the creation in vitro of a new tissue with native properties.

Correction: Catalyst supports based on ZnO-ZnAl2O4 nanocomposites with enhanced selectivity and coking resistance in isobutane dehydrogenation.

Correction for 'Catalyst supports based on ZnO-ZnAl2O4 nanocomposites with enhanced selectivity and coking resistance in isobutane dehydrogenation' by Anna N. Matveyeva et al., Dalton Trans., 2022, 51, 12213-12224, https://doi.org/10.1039/d2dt02088b.

Catalyst supports based on ZnO-ZnAl2O4 nanocomposites with enhanced selectivity and coking resistance in isobutane dehydrogenation.

Development of coking resistant supports and catalysts for hydrocarbons conversion is challenging, especially when using such acidic materials as alumina. Apparently, this problem can be mitigated by using spinels that are less acidic, being, however, thermally stable. In this study, a series of ZnO-ZnAl2O4 nanocomposites with different ZnO loading were prepared by urotropine-nitrate combustion synthesis to be used as supports for isobutane dehydrogenation catalysts. The nanocomposites were characterized by XRD, SEM, N2-physisorption analysis, EDS, H2-TPR, TPD of NH3 and tested in isobutane dehydrogenation. Spinels with small amounts of ZnO displayed higher acidity and specific surface areas than samples with a higher ZnO content (30-40 mol%). At the same time, the maximum activity and the lowest selectivity to by-products (CH4 and C3H6) after 10 min of the reaction were observed for the nanocomposite containing 20 mol% of ZnO. The obtained nanocomposites have demonstrated better resistance to coking compared to commercial alumina.

Deep-Level Emission Tailoring in ZnO Nanostructures Grown via Hydrothermal Synthesis.

Zinc oxide (ZnO) nanostructures are widely used in various fields of science and technology due to their properties and ease of fabrication. To achieve the desired characteristics for subsequent device application, it is necessary to develop growth methods allowing for control over the nanostructures' morphology and crystallinity governing their optical and electronic properties. In this work, we grow ZnO nanostructures via hydrothermal synthesis using surfactants that significantly affect the growth kinetics. Nanostructures with geometry from nanowires to hexapods are obtained and studied with photoluminescence (PL) spectroscopy. Analysis of the photoluminescence spectra demonstrates pronounced exciton on a neutral donor UV emission in all of the samples. Changing the growth medium chemical composition affects the emission characteristics sufficiently. Apart the UV emission, nanostructures synthesized without the surfactants demonstrate deep-level emission in the visible range with a peak near 620 nm. Structures synthesized with the use of sodium citrate exhibit emission peak near 520 nm, and those with polyethylenimine do not exhibit the deep-level emission. Thus, we demonstrate the correlation between the hydrothermal growth conditions and the obtained ZnO nanostructures' optical properties, opening up new possibilities for their precise control and application in nanophotonics, UV-Vis and white light sources.

Collagen Scaffolds Treated by Hydrogen Peroxide for Cell Cultivation.

Collagen in the body is exposed to a range of influences, including free radicals, which can lead to a significant change in its structure. Modeling such an effect on collagen fibrils will allow one to get a native structure in vitro, which is important for modern tissue engineering. The aim of this work is to study the effect of free radicals on a solution of hydrogen peroxide with a concentration of 0.006-0.15% on the structure of collagen fibrils in vitro, and the response of cells to such treatment. SEM measurements show a decrease in the diameter of the collagen fibrils with an increase in the concentration of hydrogen peroxide. Such treatment also leads to an increase in the wetting angle of the collagen surface. Fourier transform infrared spectroscopy demonstrates a decrease in the signal with wave number 1084 cm-1 due to the detachment of glucose and galactose linked to hydroxylysine, connected to the collagen molecule through the -C-O-C- group. During the first day of cultivating ASCs, MG-63, and A-431 cells, an increase in cell adhesion on collagen fibrils treated with H2O2 (0.015, 0.03%) was observed. Thus the effect of H2O2 on biologically relevant extracellular matrices for the formation of collagen scaffolds was shown.

Effect of crystal structure on the Young's modulus of GaP nanowires.

Young's modulus of tapered mixed composition (zinc-blende with a high density of twins and wurtzite with a high density of stacking faults) gallium phosphide (GaP) nanowires (NWs) was investigated by atomic force microscopy. Experimental measurements were performed by obtaining bending profiles of as-grown inclined GaP NWs deformed by applying a constant force to a series of NW surface locations at various distances from the NW/substrate interface. Numerical modeling of experimental data on bending profiles was done by applying Euler-Bernoulli beam theory. Measurements of the nano-local stiffness at different distances from the NW/substrate interface revealed NWs with a non-ideal mechanical fixation at the NW/substrate interface. Analysis of the NWs with ideally fixed base resulted in experimentally measured Young's modulus of 155 ± 20 GPa for ZB NWs, and 157 ± 20 GPa for WZ NWs, respectively, which are in consistence with a theoretically predicted bulk value of 167 GPa. Thus, impacts of the crystal structure (WZ/ZB) and crystal defects on Young's modulus of GaP NWs were found to be negligible.

Investigation of the Morphology and Electrical Properties of Graphene Used in the Development of Biosensors for Detection of Influenza Viruses.

In this study, we discuss the mechanisms behind changes in the conductivity, low-frequency noise, and surface morphology of biosensor chips based on graphene films on SiC substrates during the main stages of the creation of biosensors for detecting influenza viruses. The formation of phenylamine groups and a change in graphene nano-arrangement during functionalization causes an increase in defectiveness and conductivity. Functionalization leads to the formation of large hexagonal honeycomb-like defects up to 500 nm, the concentration of which is affected by the number of bilayer or multilayer inclusions in graphene. The chips fabricated allowed us to detect the influenza viruses in a concentration range of 10-16 g/mL to 10-10 g/mL in PBS (phosphate buffered saline). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed that these defects are responsible for the inhomogeneous aggregation of antibodies and influenza viruses over the functionalized graphene surface. Non-uniform aggregation is responsible for a weak non-linear logarithmic dependence of the biosensor response versus the virus concentration in PBS. This feature of graphene nano-arrangement affects the reliability of detection of extremely low virus concentrations at the early stages of disease.

Functional Polylactide Blend Films for Controlling Mesenchymal Stem Cell Behaviour.

Polymer blending is a suitable physical modification method to create novel properties of different polymers. Blending polylactic acid (PLA) and polyethylene glycol (PEG) produces materials with a wide range of properties. This study was the first to investigate the effect of different isomeric forms of PLA and PEG with terminal amino groups to obtain biocompatible films for human mesenchymal stem cell cultivation. It has been shown by scanning electron microscopy that the surface topology changes to the greatest extent when using films obtained on the basis of poly(d,l-lactide) and PEG with high molecular weights (15,000 g/mol). In order to obtain thin films and rapid evaporation of the solvent, PEG is mixed with PLA and does not form a separate phase and is not further washed out during the incubation in water. The presence of PEG with terminal hydroxyl and amino groups in blend films after incubation in water was proven using Fourier transform infrared (FTIR) spectroscopy. Results of fluorescence microscopy demonstrated that blend films formed on PLA and polyethylene glycol diamine (PEG-NH2) are more suitable for cell spreading and focal contact formation compared to cells cultured on the surface of pure PLA films or films made from PLA and PEG.

Different Conditions for the Modification of Polycaprolactone Films with L-Arginine.

Poly-ε-caprolactone (PCL) is a biodegradable polymer used in regenerative medicine. Mesenchymal stem cells (MSCs) play an important role in the regeneration of different tissues. The hydrophobicity and neutrality of a PCL surface reduce MSCs' adhesion and proliferation. In this study, PCL films were treated with arginine to improve surface hydrophilicity. The influences of arginine concentration, temperature, and solvent on PCL surface properties were investigated. PCL films treated with a solution of arginine in isopropyl alcohol were found to have the maximum number of amino groups. The greatest number of cells, 2 h after seeding, adhered to such films. It was shown that amino groups affect the interaction of cells with a modified surface and the hydrolysis reaction after treatment with isopropyl alcohol promotes the formation of adhesive focal contacts. Hence, our results illustrate that functional groups on the PCL surface after arginine solution treatment regulate MSC adhesion and focal contact formation.

Polycaprolactone Films Modified by L-Arginine for Mesenchymal Stem Cell Cultivation.

This article describes the modification conditions and properties of polymer films obtained using a solution of poly(ε-caprolactone) modified with arginine. We investigated the effects on the surface and biological properties of films created using various arginine concentrations and temperature conditions during the modification process. We found that both increasing the arginine concentration of the treatment solution or the temperature of the treatment reaction increased the arginine content of the film. Following a cellular cultivation period of 3 days, greater levels of cell proliferation were observed on all modified poly(ε-caprolactone) films compared to unmodified polymer films. Experiments using fluorescence microscopy showed that the modification conditions also had a significant effect on cellular spreading and the organization of the actin cytoskeleton following 2 h of cultivation. The degree of spreading and actin cytoskeleton organization observed in cells on these modified polymer films was superior to that of the control films.

Filtering of elastic waves by opal-based hypersonic crystal.

We report experiments in which high quality silica opal films are used as three-dimensional hypersonic crystals in the 10 GHz range. Controlled sintering of these structures leads to well-defined elastic bonding between the submicrometer-sized silica spheres, due to which a band structure for elastic waves is formed. The sonic crystal properties are studied by injection of a broadband elastic wave packet with a femtosecond laser. Depending on the elastic bonding strength, the band structure separates long-living surface acoustic waves with frequencies in the complete band gap from bulk waves with band frequencies that propagate into the crystal leading to a fast decay.