High-hydrostatic pressure technique is an effective method for the preparation of PVA–heparin hybrid gel

Utilization of Additive Manufacturing Techniques for the Development of a Novel Scaffolds with Magnetic Properties for Potential Application in Enhanced Bone Regeneration

This study focuses on designing and evaluating scaffolds with essential properties for bone regeneration, such as biocompatibility, macroporous geometry, mechanical strength, and magnetic responsiveness. The scaffolds are made using 3D printing with acrylic resin and iron oxides synthesized through solution combustion. Utilizing triply periodic minimal surfaces (TPMS) geometry and mask stereolithography (MSLA) printing, the scaffolds achieve precise geometrical features. The mechanical properties are enhanced through resin curing, and magnetite particles from synthesized nanoparticles and alluvial magnetite are added for magnetic properties. The scaffolds show a balance between stiffness, porosity, and magnetic responsiveness, with maximum compression strength between 4.8 and 9.2 MPa and Young's modulus between 58 and 174 MPa. Magnetic properties such as magnetic coercivity, remanence, and saturation are measured, with the best results from scaffolds containing synthetic iron oxides at 1% weight. The viscosity of the mixtures used for printing is between 350 and 380 mPas, and contact angles between 90° and 110° are achieved. Biocompatibility tests indicate the potential for clinical trials, though further research is needed to understand the impact of magnetic properties on cellular interactions and optimize scaffold design for specific applications. This integrated approach offers a promising avenue for the development of advanced materials capable of promoting enhanced bone regeneration.

Recent Advances in the Fabrication and Performance Optimization of Polyvinyl Alcohol Based Vascular Grafts

Cardiovascular disease is one of the diseases with the highest morbidity and mortality rates worldwide, and coronary artery bypass grafting (CABG) is a fast and effective treatment. More researchers are investigating in artificial blood vessels due to the limitations of autologous blood vessels. Despite the availability of large-diameter vascular grafts (Ø > 6 mm) for clinical use, small-diameter vascular grafts (Ø < 6 mm) have been a challenge for researchers to overcome in recent years. Vascular grafts made of polyvinyl alcohol (PVA) and PVA-based composites have excellent biocompatibility and mechanical characteristics. In order to gain a clearer and more specific understanding of the progress in PVA vascular graft research, particularly regarding the preparation methods, principles, and functionality of PVA vascular graft, this article discusses the mechanical properties, biocompatibility, blood compatibility, and other properties of PVA vascular graft prepared or enhanced with different blends using various techniques that mimic natural blood vessels. The findings reveal the feasibility and promising potential of PVA or PVA-based composite materials as vascular grafts.

Effects of Non-Conventional Sterilisation Methods on PBO-Reinforced PVA Hydrogels for Cartilage Replacement

Articular cartilage (AC) degradation is a recurrent pathology that affects millions of people worldwide. Polyvinyl alcohol (PVA) hydrogels have been widely explored for AC replacement. However, their mechanical performance is generally inadequate, and these materials need to be reinforced. Moreover, to be used in a clinical setting, such materials must undergo effective sterilisation. In this work, a PVA hydrogel reinforced with poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibres was submitted to three non-conventional sterilisation methods: microwave (MW), high hydrostatic pressure (HHP), and plasma (PM), in order to evaluate their impact on the properties of the material. Sterilisation was achieved in all cases. Properties such as water content and hydrophilicity were not affected. FTIR analysis indicated some changes in crystallinity and/or crosslinking in all cases. MW was revealed to be the most suitable method, since, unlike to PM and HHP, it led to a general improvement of the materials’ properties: increasing the hardness, stiffness (both in tensile and compression), and shear modulus, and also leading to a decrease in the coefficient of friction against porcine cartilage. Furthermore, the samples remained non-irritant and non-cytotoxic. Moreover, this method allows terminal sterilisation in a short time (3 min) and using accessible equipment.

Biomedical applications of carbohydrate-based polyurethane: From biosynthesis to degradation

The foremost common natural polymers are carbohydrate-based polymers or polysaccharides, having a long chain of monosaccharide or disaccharide units linked together via a glycosidic linkage to form a complex structure. There are several uses of carbohydrate-based polymers in biomedical sector due to its attractive features including less toxicity, biocompatibility, biodegradability, high reactivity, availability, and relatively inexpensive. The aim of our study was to explore the synthetic approaches for the preparation of numerous carbohydrate-based polyurethanes (PUs) and their wide range of pharmaceutical and biomedical applications. The data summarized in this study shows that the addition of carbohydrates in the structural skeleton of PUs not only improve their suitability but also effect the applicability for employing them in biological applications. Carbohydrate-based units are incorporated into the PUs, which is the most convenient method for the synthesis of novel biocompatible and biodegradable carbohydrate-based PUs to use in various biomedical applications.

A synergy between dopamine and electrostatically bound bactericide in a poly (vinyl alcohol) hybrid hydrogel for treating infected wounds

Antibacterial hydrogels have emerged as viable options for battling infections associated with impaired wound healing. It is challenging in developing antibacterial hydrogels that have sustained and stable bactericidal activity while avoiding the use of any agents that may adversely affect safety. In view of this concern, a multi-functional polyvinyl alcohol (PVA)/sodium alginate-dopamine (SA-DA) hydrogel matrix-based wound dressing embedding with bis-quaternary triphenyl-phosphonium salt (BTPP+), that would present long-term intrinsic antimicrobial properties was developed using freeze-thawing (F-T) method herein. DA endows the hydrogel with efficient bacteria capture ability and subsequently the captured bacterial pathogens were in situ killed by electrostatically bound BTPP+, and hence significantly augmented the antibacterial efficacy. Furthermore, DA, co-operating with BTPP+ could promote erythrocyte and platelet aggregation on hydrogels, which ensures hydrogels with improved hemostasis capacity. Thus, this investigation provides a feasible simple avenue for development of long-term intrinsic antimicrobial hydrogel dressings with efficient hemostasis efficacy for infected wounds.

PLA-Collagen Composite Scaffold Fabrication by Vacuum Pressure Impregnation

Composite scaffolds are made by various methods, such as copolymerization, freeze gelation, and thermally induced phase separation, which can compound materials with different properties using solvents and heat. However, it is difficult to compound solvents and heat-sensitive materials such as natural polymers. In this study, we investigated a vacuum pressure impregnation (VPI) method for creating a composite of natural polymers. A collagen solution could not be introduced into a poly (l-lactide) (PLA) porous material using an immersing treatment, but it is possible using the VPI method. The resulting PLA-collagen composite scaffold had greater water adsorption and degradation than a PLA scaffold. These results indicate that VPI may be a promising method for creating composites of natural materials. Impact Statement This is the development of a method for introducing cells into a completed porous material in a short time. This technology is expected to be applied to tissue regeneration and 3D culture.

Heparin-functionalized hydrogels as growth factor-signaling substrates

Tuneable, bioactive hydrogels present an attractive option as cell-instructive substrates for tissue regeneration. Properties mimicking the extracellular matrix at the site of injury are sought after, in particular the ability to regulate growth factors that are key to the regeneration process. This study demonstrates the successful formation of hydrogels with heparin functionalities and fibroblast growth factor-2 (FGF-2). Poly(2-hydroxyethyl methacrylate)-heparin hydrogels were capable of retaining FGF-2 by specific binding to heparin and subsequently showed sustained presentation of the growth factor to mesenchymal stromal cells (MSC). Heparin acted as stable anchoring molecules for FGF-2 on the substrate and the synergistic effect of the ensuing heparin-FGF-2 complex was evident in supporting long term cell growth. The presence of heparin during 3D scaffold formation was also found to introduce surface roughness and microporosity to the resulting hydrogels. While FGF-2 has been known to encourage MSC growth and maintain their multilineage potential, other heparin-binding ligands such as bone morphogenetic proteins are potent differentiation stimuli for MSC. Therefore preserving MSC multipotency or a push toward a differentiation pathway may be pursued by the choice of ligand applied to and bound by the heparin functionalities on the current substrate.

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.

Voriconazole Composited Polyvinyl Alcohol/Hydroxypropyl-β-Cyclodextrin Nanofibers for Ophthalmic Delivery

Voriconazole (VRC) incorporated in composited polyvinyl alcohol (PVA)/hydroxypropyl-β-cyclodextrin (HPβCD) blended nanofibers were produced via electrospinning for efficient ophthalmic delivery. The VRC loading capacity increased with increasing HPβCD content. The optimal solution for electrospinning consisted of 8% (w/v) PVA, 4% (w/v) HPβCD and 0.5% (w/v) VRC. The nanofibers exhibited bead-free average fiber diameters of 307±31 nm and VRC was released in vitro in a sustained manner. The VRC nanofibers were characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The proton nuclear magnetic resonance (1H-NMR) was used to analyze the molar ratio of HPβCD/VRC in the nanofibers. Compared with a VRC solution, the nanofibers significantly prolonged the half life, and increased the bioavailability of VRC in rabbit tears. No obvious signs of irritation were observed after application in the conjunctival sac. VRC nanofibers are promising for ophthalmic drug delivery and further pharmacodynamics studies are needed.

Plasma functionalization of poly(vinyl alcohol) hydrogel for cell adhesion enhancement

Tailoring the interface interactions between a biomaterial and the surrounding tissue is a capital aspect to consider for the design of medical devices. Poly(vinyl alcohol) (PVA) hydrogels present suitable mechanical properties for various biological substitutes, however the lack of cell adhesion on their surface is often a problem. The common approach is to incorporate biomolecules, either by blending or coupling. But these modifications disrupt PVA intra- and intermolecular interactions leading therefore to a loss of its original mechanical properties. In this work, surface modification by glow discharge plasma, technique known to modify only the surface without altering the bulk properties, has been investigated to promote cell attachment on PVA substrates. N2/H2 microwave plasma treatment has been performed, and the chemical composition of PVA surface has been investigated. X-ray photoelectron and Fourier transform infrared analyses on the plasma-treated films revealed the presence of carbonyl and nitrogen species, including amine and amide groups, while the main structure of PVA was unchanged. Plasma modification induced an increase in the PVA surface wettability with no significant change in surface roughness. In contrast to untreated PVA, plasma-modified films allowed successful culture of mouse fibroblasts and human endothelial cells. These results evidenced that the grafting was stable after rehydration and that it displayed cell adhesive properties. Thus plasma amination of PVA is a promising approach to improve cell behavior on contact with synthetic hydrogels for tissue engineering.

Preparation of a Nanoscaled Poly(vinyl alcohol)/Hydroxyapatite/DNA Complex Using High Hydrostatic Pressure Technology for In Vitro and In Vivo Gene Delivery

Our previous research showed that poly(vinyl alcohol) (PVA) nanoparticles incorporating DNA with hydrogen bonds obtained by high hydrostatic pressurization are able to deliver DNA without any significant cytotoxicity. To enhance transfection efficiency of PVA/DNA nanoparticles, we describe a novel method to prepare PVA/DNA nanoparticles encapsulating nanoscaled hydroxyapatites (HAps) prepared by high hydrostatic pressurization (980 MPa), which is designed to facilitate endosomal escape induced by dissolving HAps in an endosome. Scanning electron microscopic observation and dynamic light scattering measurement revealed that HAps were significantly encapsulated in PVA/HAp/DNA nanoparticles. The cytotoxicity, cellular uptake, and transgene expression of PVA/HAp/DNA nanoparticles were investigated using COS-7 cells. It was found that, in contrast to PVA/DNA nanoparticles, their internalization and transgene expression increased without cytotoxicity occurring. Furthermore, a similar level of transgene expression between plasmid DNA and PVA/HAp/DNA nanoparticles was achieved using in vivo hydrodynamic injection. Our results show a novel method of preparing PVA/DNA nanoparticles encapsulating HAp nano-crystals by using high hydrostatic pressure technology and the potential use of HAps as an enhancer of the transfection efficiency of PVA/DNA nanoparticles without significant cytotoxicity.