Arabinoxylan-based psyllium seed hydrocolloid: Single-step aqueous extraction and use in tissue engineering

Biomacromolecules derived from natural sources offer superior biocompatibility, biodegradability, and water-holding capacity, which make them promising scaffolds for tissue engineering. Psyllium seed has gained attention in biomedical applications recently due to its gel-forming ability, which is provided by its polysaccharide-rich content consisting mostly of arabinoxylan. This study focuses on the extraction and gelation of Psyllium seed hydrocolloid (PSH) in a single-step water-based protocol, and scaffold fabrication using freeze-drying method. After characterization of the scaffold, including morphological, mechanical, swelling, and protein adsorption analyses, 3D cell culture studies were done using NIH-3 T3 fibroblast cells on PSH scaffold, and cell viability was assessed using Live/Dead and Alamar Blue assays. Starting from day 1, high cell viability was obtained, and it reached 90 % at the end of 15-day culture period. Cellular morphology on PSH scaffold was monitored via SEM analysis; cellular aggregates then spheroid formation were observed throughout the study. Collagen Type-I and F-actin expressions were followed by immunostaining revealing a 9- and 10-fold increase during long-term culture. Overall, a single-step and non-toxic protocol was developed for extraction and gelation of PSH. Obtained results unveiled that PSH scaffold provided a favorable 3D microenvironment for cells, holding promise for further tissue engineering applications.

3D Printable Active Hydrogels with Supramolecular Additive-Driven Adaptiveness

Smart hydrogels are a promising candidate for the development of next-generation soft materials due to their stimuli-responsiveness, deformability, and biocompatibility. However, it remains challenging to enable hydrogels to actively adapt to various environmental conditions like living organisms. In this work, supramolecular additives are introduced to the hydrogel matrix to confer environmental adaptiveness. Specifically, their microstructures, swelling behaviors, mechanical properties, and transparency can adapt to external environmental conditions. Moreover, the presence of hydrogen bonding provides the hydrogel with applicable rheological properties for 3D extrusion printing, thus allowing for the facile preparation of thickness-dependent camouflage and multistimuli responsive complex. The environmentally adaptive hydrogel developed in this study offers new approaches for manipulating supramolecular interactions and broadens the capability of smart hydrogels in information security and multifunctional integrated actuation.

Composite Cryogels Based on Hydroxyapatite and Polyvinyl Alcohol and the Study of Physicochemical and Mechanical Properties

Nowadays, due to the increasing number of diseases and injuries related to bone tissue, there is an acute problem of creating a material that could be incorporated into the bone tissue structure and contribute to accelerated bone regeneration. Such materials can be represented by a polymeric matrix that holds the material in the bone and an inorganic component that can be incorporated into the bone structure and promote accelerated bone regeneration. Therefore, in this work we investigated polyvinyl alcohol-based composite cryogels containing an in situ deposited inorganic filler, hydroxyapatite. The freezing temperature was varied during the synthesis process. The composition of the components was determined by infrared spectroscopy and the phase composition by X-ray phase analysis, from which it was found that the main phase of the composite is hydroxyapatite and that the particle size decreases with increasing freezing temperature. The elemental composition of the surface is dominated by carbon, oxygen, phosphorus and calcium; no impurities of other elements not typical for polyvinyl alcohol/ hydroxyapatite cryogels were found. Higher mechanical properties and melting points were observed at -15 °C. Cryogenic treatment parameters did not affect cell viability; however, cell viability was above 80% in all samples.

Chitosan hydrogels with MK2 inhibitor peptide-loaded nanoparticles to treat atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that lacks ideal long-term treatment options due to a series of side effects, such as skin atrophy, related to the most common treatment prescribed to manage moderate-to-severe AD. In this study, a cell-penetrating MK2 inhibitor peptide YARA (YARAAARQARAKALNRQGLVAA) was loaded into hollow thermo-responsive pNIPAM nanoparticles (NP), which were further incorporated into chitosan hydrogels (H-NP-YARA) to promote local drug delivery, improve moisture and the anti-inflammatory activity. The NPs exhibited high loading efficiency (>50%) and the hydrogel remained porous following NP incorporation as observed by scanning electron microscopy (SEM). Both nanoparticles and hydrogels were able to improve the release of YARA and sustained release to up to 120 h. The hydrogels and NPs delivered 2 and 4-fold more YARA into viable skin layers of porcine skin in vitro at 12 h post-application than the non-encapsulated compound in intact and impaired barrier conditions. Furthermore, the YARA-loaded NPs (NP-YARA) and H-NP-YARA treatment decreased the levels of inflammatory cytokines up to 20 time-fold compared with the non-treated group of human keratinocytes under inflammatory conditions. Consistent with the results in cell culture, the loading of YARA in NP reduced the levels of IL-1β, IL-6, and TNF-α up to 3.3 times in an ex vivo skin culture model after induction of inflammation. A further decrease of up to 17 times-fold was observed with H-NP-YARA treatment compared to the drug in solution. Our data collectively suggest that chitosan hydrogel containing YARA-loaded nanoparticles is a promising new formulation for the topical treatment of AD.

Unidirectional Nanopore Dehydration Induces an Anisotropic Polyvinyl Alcohol Hydrogel Membrane with Enhanced Mechanical Properties

As a biocompatible, degradable polymer material, polyvinyl alcohol (PVA) can have a wide range of applications in the biomedical field. PVA aqueous solutions at room temperature can be cast into very thin films with poor mechanical strength via water evaporation. Here, we describe a novel dehydration method, unidirectional nanopore dehydration (UND). The UND method was used to directly dehydrate a PVA aqueous solution to form a water-stable, anisotropic, and mechanically robust PVA hydrogel membrane (PVAHM), whose tensile strength, elongation at break, and swelling ratio reached values of up to ~2.95 MPa, ~350%, and ~350%, respectively. The film itself exhibited an oriented arrangement of porous network structures with an average pore size of ~1.0 μm. At 70 °C, the PVAHMs formed were even more mechanically robust, with a tensile strength and elongation at break of 10.5 MPa and 891%, almost 3.5 times and 2 times greater than the PVAHM prepared at 25 °C, respectively. The processing temperature affects the velocity at which the water molecules flow unidirectionally through the nanopores, and could, thus, alter the overall transformation of the PVA chains into a physically crosslinked 3D network. Therefore, the temperature setting during UND can control the mechanical properties of the hydrogel membrane to meet the requirements of various biomaterial applications. These results show that the UND can induce the ordered rearrangement of PVA molecular chains, forming a PVAHM with superior mechanical properties and exhibiting a greater number of stronger hydrogen bonds. Therefore, the novel dehydration mode not only induces the formation of a mechanically robust and anisotropic PVA hydrogel membrane with a porous network structure and an average pore size of ~1.0 μm, but also greatly enhances the mechanical properties by increasing the temperature. It may be applied for the processing of water-soluble polymers, including proteins, as novel functional materials.

Cellulose nanofibers/PVA blend polymeric beads containing in-situ prepared magnetic nanorods as dye pollutants adsorbents

Magnetic beads were developed from polyvinyl alcohol and different amounts of cellulose nanofibers (CNF) by in-situ preparation of iron oxide nanoparticles in an alkaline aqueous medium at room temperature. The CNF were isolated from wheat straw, whereas the magnetic nanoparticles (MNPs) precursors were simple iron salts. The complete characterization of all the obtained materials was conducted, and among some other outstanding results it showed that all the components were strongly interacting via hydrogen bonding, while the nano-rods and husks like MNPs were effectively acting as crosslinking dots. All the prepared materials had good magnetic responses, and they were able to remove not only cationic, but also anionic dye pollutants from aqueous model solutions.

3D-Printed Hydrogels in Orthopedics: Developments, Limitations, and Perspectives

Three-dimensional (3D) printing has been used in medical research and practice for several years. Various aspects can affect the finished product of 3D printing, and it has been observed that the impact of the raw materials used for 3D printing is unique. Currently, hydrogels, including various natural and synthetic materials, are the most biologically and physically advantageous biological raw materials, and their use in orthopedics has increased considerably in recent years. 3D-printed hydrogels can be used in the construction of extracellular matrix during 3D printing processes. In addition to providing sufficient space structure for osteogenesis and chondrogenesis, hydrogels have shown positive effects on osteogenic and chondrogenic signaling pathways, promoting tissue repair in various dimensions. 3D-printed hydrogels are currently attracting extensive attention for the treatment of bone and joint injuries owing to the above-mentioned significant advantages. Furthermore, hydrogels have been recently used in infection prevention because of their antiseptic impact during the perioperative period. However, there are a few shortcomings associated with hydrogels including difficulty in getting rid of the constraints of the frame, poor mechanical strength, and burst release of loadings. These drawbacks could be overcome by combining 3D printing technology and novel hydrogel material through a multi-disciplinary approach. In this review, we provide a brief description and summary of the unique advantages of 3D printing technology in the field of orthopedics. In addition, some 3D printable hydrogels possessing prominent features, along with the key scope for their applications in bone joint repair, reconstruction, and antibacterial performance, are discussed to highlight the considerable prospects of hydrogels in the field of orthopedics.

Photo-crosslinking and surface-attachment of polyvinyl alcohol nanocoatings by C,H insertion to customize their swelling behavior and stability in polar media

Benzophenone-modified polyvinyl alcohol is synthesized, processed to nanocoatings and converted to UV-crosslinked surface-bound polymer networks.

Drug Amorphous Solid Dispersions Based on Poly(vinyl Alcohol): Evaluating the Effect of Poly(propylene Succinate) as Plasticizer

Although significant actions have been taken towards the utilization of poly(vinyl alcohol) (PVA) in the preparation of drug amorphous solid dispersions (ASDs) using fusion-based techniques (such as melt-quench cooling and hot-melt extrusion), several drawbacks regarding its rather high melting temperature and its thermal degradation profile make the use of the polymer extremely challenging. This is especially important when the active pharmaceutical ingredient (API) has a lower melting temperature (than PVA) or when it is thermally labile. In this vein, a previous study showed that newly synthesized polyester-based plasticizers may improve the processability and the thermal properties of PVA. However, the effects of such polyester-based plasticizers on the drug’s physicochemical and pharmaco-technical properties are yet unknown. Hence, the aim of the present study is to extend our previous findings and evaluate the use of poly(propylene succinate) (PPSu, i.e., the most promising plasticizer in regard to PVA) in the preparation of drug-loaded PVA-based ASDs. Dronedarone (DRN), a poorly water-soluble API, was selected as a model drug, and drug ASDs (using either neat PVA or PVA-PPSu) were prepared using the melt-mixing/quench cooling approach at low melting temperatures (i.e., 170 °C). DSC and pXRD analysis showed that a portion of the API remained crystalline in the ASDs prepared only with the use of neat PVA, while the samples having PPSu as a plasticizer were completely amorphous. Further evaluation with ATR-FTIR spectroscopy revealed the formation of significant intermolecular interactions between the API and the PVA-PPSu matrix, which could explain the system’s physical stability during storage. Finally, dissolution studies, conducted under nonsink conditions, revealed that the use of PVA-PPSu is able to maintain DRN’s sustained supersaturation for up to 8 h.

Ultrahigh-water-content biocompatible gelatin-based hydrogels: Toughened through micro-sized dissipative morphology as an effective strategy

Fabrication of simultaneously robust and superabsorbent gelatin-based hydrogels for biomedical applications still remains a challenge due to lack of locally dissipative points in the presence of large water content. Here, we apply a synthesis strategy through which water absorbency and energy dissipative points are separated, and toughening mechanism is active closely at the crack tip. For this, gelatin-based microgels (GeMs) were synthesized in a way that concentrated supramolecular interactions were present to increase the energy necessary to propagate a macroscopic crack. The microgels were interlocked to each other via both temporary hydrophobic associations and permanent covalent crosslinks, in which the sacrificial binds sustained the toughness due to the mobility of the junction zones and particles sliding. However, chemical crosslinking points preserved the integrity and fast recoverability of the hydrogel. Hysteresis increased strongly with increasing supramolecular interactions within the network. The prepared hydrogels showed energy loss and swelling ratio up to 3440 J. m^-3 and 830%, respectively, which was not achievable with conventional network fabrication methods. The microgels were also assessed for their in vivo biocompatibility in a rat subcutaneous pocket assay. Results of hematoxylin and eosin (H&E) staining demonstrated regeneration of the tissue around the scaffolds without incorporation of growth factors. Also, vascularization within the scaffolds was observed after 4 weeks implantation. These results indicate that our strategy is a promising method to manipulate those valuable polymers, which lose their toughness and applicability with increasing their water content.

Mechanical behaviors and probabilistic multiphase network model of polyvinyl alcohol hydrogel after being immersed in sodium hydroxide solution

Because of the advantages of a uniform distribution of reinforcing particles and in situ preparation, in situ precipitation has become an important way to prepare magnetic and other smart hydrogels. An important step in this process is to immerse hydrogels in alkaline solution to implant magnetic particles. Previous studies generally have ignored the effect of this process on the network structure and mechanical properties of hydrogels. In this study, we immersed polyvinyl alcohol (PVA) hydrogel samples in sodium hydroxide solutions of different concentrations to study changes in mechanical properties, such as stress–strain relationship, self-recovery, and fracture failure. The results showed that after the immersion process, the hydrogel's tensile and compressive properties changed significantly, and the failure behavior changed from brittle fracture to ductile fracture. Through a microscopic mechanism, the alkaline solution caused a high degree of phase separation and crystallization within the polymer network, thereby changing the PVA hydrogel network from a single phase to a multiphase. Hence, we used a continuous multiphase network model with a certain probability distribution to describe this tensile behavior. This model well described the stress–strain relationship of the hydrogel from stretching to fracture and revealed that the macroscopic failure corresponded to the peak of fracture distribution. Studies have shown that attention should be paid to the influence of the in situ precipitation on the mechanical properties, and the probabilistic multiphase network model can be used to predict the mechanical behavior of hydrogels with multiple phase separation.

Phase separation occurs in polyvinyl alcohol hydrogel after being immersed in sodium hydroxide solution. The change of the network structure leads to significant changes in the mechanical behaviors.

Cryostructuring of Polymeric Systems. 55. Retrospective View on the More than 40 Years of Studies Performed in the A.N.Nesmeyanov Institute of Organoelement Compounds with Respect of the Cryostructuring Processes in Polymeric Systems

The processes of cryostructuring in polymeric systems, the techniques of the preparation of diverse cryogels and cryostructurates, the physico-chemical mechanisms of their formation, and the applied potential of these advanced polymer materials are all of high scientific and practical interest in many countries. This review article describes and discusses the results of more than 40 years of studies in this field performed by the researchers from the A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences-one of the key centers, where such investigations are carried out. The review includes brief historical information, the description of the main effects and trends characteristic of the cryostructuring processes, the data on the morphological specifics inherent in the polymeric cryogels and cryostructurates, and examples of their implementation for solving certain applied tasks.

Tough and Low Friction Polyvinyl Alcohol Hydrogels Loaded with Anti-inflammatories for Cartilage Replacement

The development of new materials that mimic cartilage and its function is an unmet need that will allow replacing the damaged parts of the joints, instead of the whole joint. Polyvinyl alcohol (PVA) hydrogels have raised special interest for this application due to their biocompatibility, high swelling capacity and chemical stability. In this work, the effect of post-processing treatments (annealing, high hydrostatic pressure (HHP) and gamma-radiation) on the performance of PVA gels obtained by cast-drying was investigated and, their ability to be used as delivery vehicles of the anti-inflammatories diclofenac or ketorolac was evaluated. HHP damaged the hydrogels, breaking some bonds in the polymeric matrix, and therefore led to poor mechanical and tribological properties. The remaining treatments, in general, improved the performance of the materials, increasing their crystallinity. Annealing at 150 °C generated the best mechanical and tribological results: higher resistance to compressive and tensile loads, lower friction coefficients and ability to support higher loads in sliding movement. This material was loaded with the anti-inflammatories, both without and with vitamin E (Vit.E) or Vit.E + cetalkonium chloride (CKC). Vit.E + CKC helped to control the release of the drugs which occurred in 24 h. The material did not induce irritability or cytotoxicity and, therefore, shows high potential to be used in cartilage replacement with a therapeutic effect in the immediate postoperative period.

Noncovalent Muscle-Inspired Hydrogel with Rapid Recovery and Antifatigue Property under Cyclic Stress

Designing muscle-inspired hydrogels that possess structure and bioactivity similar to muscles is an eternal pursuit in material sciences and tissue engineering. However, the development of a muscle-inspired hydrogel via the formation of noncovalent interactions remains challenging, and its application in sustained loading situations such as cyclic stresses is limited. Herein, H-bonds and microcrystalline domains were introduced, and a noncovalent muscle-inspired hydrogel was developed to mimic both the physical structure and functionality of muscles at the macroscopic level. The hydrogel exhibited excellent mechanical properties (a fracture strength of 2.16 ± 0.08 MPa, fracture strain of 830 ± 23%, elastic modulus of 275 ± 9 KPa, and toughness of 7.04 ± 0.80 MJ/m³), a large energy dissipation (2.00 ± 0.27 MJ/m³ at 600% elongation), and a rapid self-recovery (92 ± 1% toughness recovery within 20 min). Antifatigue behavior of the muscle-inspired hydrogel was observed upon successive tensile and compressive cyclic loadings. Under 100 cycles of loadings, the robustness of the hydrogel has been maintained and even improved, which are achieved due to strain-induced orientation. Furthermore, the hydrogel was found to be self-healed. This hydrogel promises to be among the most relevant drivers for the development of new-generation muscle-inspired hydrogels in the next decade.

Influence of stabilizer type and concentration on the lung deposition and retention of resveratrol nanosuspension-in-microparticles

The purpose of this study was to explore the influence of stabilizer type and concentration on the properties of spray dried nanosuspension-in-microparticles (NS-in-MPs) for inhalation. Taking resveratrol (RES) as a Biopharmaceutical Classification System II (BCS II) model drug, the RES containing nanosuspensions were fabricated by high pressure homogenization method with different stabilizers including sodium dodecyl sulphate (SDS), sodium alginate (SA), chitosan (CS) and polyvinyl alcohol (PVA). Then, the nanosuspensions were spray dried with mannitol to obtain inhalable NS-in-MPs. The particle size, morphology, drug existing state, in vitro aerodynamic performance, in vitro release behavior, lung retention and pharmacokinetic behaviors were characterized. It was found that the morphology, lung deposition as well as in vitro drug release from the microparticles were significantly influenced by stabilizer type, with 1% PVA as stabilizer presenting the highest fine particle fraction (FPF). Meanwhile, taking PVA as an example, it was found stabilizer concentration could alter morphology and flowability of the microparticles, and the FPF value decreased with the increase of stabilizer concentration. Further drug retention and in vivo pharmacokinetic studies demonstrated that the positively charged stabilizer CS could facilitate drug retention and minimize drug expose to the systemic circulation. In conclusion, the deposition and lung retention behavior of NS-in-MPs could be well tuned by selecting different type or concentration of stabilizers, which could facilitate local lung diseases therapy.

Cryostructuring of Polymeric Systems. 50.† Cryogels and Cryotropic Gel-Formation: Terms and Definitions

A variety of cryogenically-structured polymeric materials are of significant scientific and applied interest in various areas. However, in spite of considerable attention to these materials and intensive elaboration of their new examples, as well as the impressive growth in the number of the publications and patents on this topic over the past two decades, a marked variability of the used terminology and definitions is frequently met with in the papers, reviews, theses, patents, conference presentations, advertising materials and so forth. Therefore, the aim of this brief communication is to specify the basic terms and definitions in the particular field of macromolecular science.

Reproduction method for dried biomodels composed of poly (vinyl alcohol) hydrogels

Models mimicking the realistic geometries and mechanical properties of human tissue are requiring ever-better materials. Biomodels made of poly (vinyl alcohol) are particularly in demand, as they can be used to realistically reproduce the characteristics of blood vessels. The reproducibility of biomodels can be altered due to dehydration that is observed after long periods of usage. In order to improve their usability, one should consider the method used to reproduce them; however, few studies have reported a method reproduce biomodels. This study proposes a novel reproduction method for biomodels that allows them to quickly and easily reproduce their geometric and mechanical properties. Specimens of the dried biomodels were reformed through immersion in temperature-controlled water. Our results show that water at 35 °C can be effective to reproduce both the geometric and mechanical properties of the specimens. X-ray diffraction (XRD) measurements revealed that water immersion can reform the crystal structure of the pre-dried specimens, and images obtained using micro-computed tomography acquisition show that the geometry of the specimens can be reformed by water immersion without introducing any defects. These results indicate that the proposed method can lead to high reproducibility of both the original geometric and mechanical properties of the dried biomodels.

Biomaterial Scaffolds in Regenerative Therapy of the Central Nervous System

The central nervous system (CNS) is the most important section of the nervous system as it regulates the function of various organs. Injury to the CNS causes impairment of neurological functions in corresponding sites and further leads to long-term patient disability. CNS regeneration is difficult because of its poor response to treatment and, to date, no effective therapies have been found to rectify CNS injuries. Biomaterial scaffolds have been applied with promising results in regeneration medicine. They also show great potential in CNS regeneration for tissue repair and functional recovery. Biomaterial scaffolds are applied in CNS regeneration predominantly as hydrogels and biodegradable scaffolds. They can act as cellular supportive scaffolds to facilitate cell infiltration and proliferation. They can also be combined with cell therapy to repair CNS injury. This review discusses the categories and progression of the biomaterial scaffolds that are applied in CNS regeneration.

Effect of Gamma Ray Irradiation on Friction Property of Poly(vinyl alcohol) Cast-Drying on Freeze-Thawed Hybrid Gel

Poly(vinyl alcohol) (PVA) is a biocompatible polymer with low toxicity. It is possible to prepare physically cross-linked PVA gels having hydrogen bonds without using a cross-linking agent. The newly reported physically cross-linked PVA cast-drying (CD) on freeze-thawed (FT) hybrid gel has an excellent friction property, which is expected to be applied as a candidate material for artificial cartilage. Gamma ray sterilization for clinical applications usually causes additional chemical cross-linking and changes physical properties of gels. In this study, CD on FT hybrid gels were irradiated using gamma rays at a different dose rate and irradiance. The results showed the optimized irradiation conditions for gamma irradiated gels to retain excellent friction characteristics.

High-Performance PVC Gel for Adaptive Micro-Lenses with Variable Focal Length

This paper presents a bio-inspired adaptive micro-lens with electrically tunable focus made of non-ionic high-molecular-weight polyvinyl chloride (PVC) gel. The optical device mimics the design of the crystalline lens and ciliary muscle of the human eye. It consists of a plano-convex PVC gel micro-lens on Indium Tin Oxide (ITO) glass, confined with an annular electrode operating as an artificial ciliary muscle. Upon electrical activation, the electroactive adhesive force of the PVC gel is exerted on the annular anode electrode, which reduces the sagittal height of the plano-convex PVC gel lens, resulting in focal length variation of the micro-lens. The focal length increases from 3.8 mm to 22.3 mm as the applied field is varied from 200 V/mm to 800 V/mm, comparable to that of the human lens. The device combines excellent optical characteristics with structural simplicity, fast response speed, silent operation, and low power consumption. The results show the PVC gel micro-lens is expected to open up new perspectives on practical tunable optics.