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In the present study, a hybrid microsphere/hydrogel system, consisting of polyvinyl alcohol (PVA)/sodium alginate (SA) hydrogel incorporating PCL microspheres is introduced as a skin scaffold to accelerate wound healing. The hydrogel substrate was developed using the freeze-thawing method, and the proportion of the involved polymers in its structure was optimized based on the in-vitro assessments. The bFGF-encapsulated PCL microspheres were also fabricated utilizing the double-emulsion solvent evaporation technique. The achieved freeze-dried hybrid system was then characterized by in-vitro and in-vivo experiments. The results obtained from the optimization of the hydrogel showed that increasing the concentration of SA resulted in a more porous structure, and higher swelling ability, elasticity and degradation rate, but decreased the maximum strength and elongation at break. The embedding of PCL microspheres into the optimized hydrogel structure provided sustained and burst-free release kinetics of bFGF. Besides, the addition of drug-loaded microspheres led to no significant change in the degradation mechanism of the hydrogel substrate; however, it reduced its mechanical strength. Furthermore, the MTT assay represented no cytotoxic effect for the hybrid system. The in-vivo studies on a burn-wound rat model, including the evaluation of the wound closure mechanism, and histological analyses indicated that the fabricated scaffold efficiently contributed to promoting cell-induced tissue regeneration and burn-wound healing.

Micro-supercapacitors are promising energy storage devices that can complement or even replace batteries in miniaturized portable electronics and microelectromechanical systems. Their main limitation, however, is the low volumetric energy density when compared with batteries. Here, we describe a hierarchically structured carbon microfibre made of an interconnected network of aligned single-walled carbon nanotubes with interposed nitrogen-doped reduced graphene oxide sheets. The nanomaterials form mesoporous structures of large specific surface area (396 m 2  g −1 ) and high electrical conductivity (102 S cm −1 ). We develop a scalable method to continuously produce the fibres using a silica capillary column functioning as a hydrothermal microreactor. The resultant fibres show a specific volumetric capacity as high as 305 F cm −3 in sulphuric acid (measured at 73.5 mA cm −3 in a three-electrode cell) or 300 F cm −3 in polyvinyl alcohol (PVA)/H 3 PO 4 electrolyte (measured at 26.7 mA cm −3 in a two-electrode cell). A full micro-supercapacitor with PVA/H 3 PO 4 gel electrolyte, free from binder, current collector and separator, has a volumetric energy density of ∼6.3 mWh cm −3 (a value comparable to that of 4 V–500 µAh thin-film lithium batteries) while maintaining a power density more than two orders of magnitude higher than that of batteries, as well as a long cycle life. To demonstrate that our fibre-based, all-solid-state micro-supercapacitors can be easily integrated into miniaturized flexible devices, we use them to power an ultraviolet photodetector and a light-emitting diode. Hierarchical hybrid carbon fibres consisting of a network of nitrogen-doped reduced graphene oxide and single-walled carbon nanotubes are synthesized and subsequently used to make a supercapacitor with high volumetric energy density.

Adhesives typically fall into two categories: those that have high but irreversible adhesion strength due to the formation of covalent bonds at the interface and are slow to deploy, and others that are fast to deploy and the adhesion is reversible but weak in strength due to formation of noncovalent bonds. Synergizing the advantages from both categories remains challenging but pivotal for the development of the next generation of wound dressing adhesives. Here, we report a fast and reversible adhesive consisting of dynamic boronic ester covalent bonds, formed between poly(vinyl alcohol) (PVA) and boric acid (BA) for potential use as a wound dressing adhesive. Mechanical testing shows that the adhesive film has strength in shear of 61 N/cm² and transcutaneous adhesive strength of 511 N/cm², generated within 2 min of application. Yet the film can be effortlessly debonded when exposed to excess water. The mechanical properties of PVA/BA adhesives are tunable by varying the cross-linking density. Within seconds of activation by water, the surface boronic ester bonds in the PVA/BA film undergo fast debonding and instant softening, leading to conformal contact with the adherends and reformation of the boronic ester bonds at the interface. Meanwhile, the bulk film remains dehydrated to offer efficient load transmission, which is important to achieve strong adhesion without delamination at the interface. Whether the substrate surface is smooth (e.g., glass) or rough (e.g., hairy mouse skin), PVA/BA adhesives demonstrate superior adhesion compared to the most widely used topical skin adhesive in clinical medicine, Dermabond.

Poly(vinylidene fluoride) (PVDF) is common polymer for electrospinning, however, its high hydrophobicity is a major drawback, which cause fouling. To introduce hydrophilicity and antibacterial activity, quaternary ammonium-functionalized amphiphilic diblock copolymers were synthesized and blended with a PVDF/graphene oxide (GO) solution, then, electrospun and coated with a hydrophilic polymer, poly(vinyl alcohol) (PVA). The amphiphilic block copolymer, consisting of a hydrophobic poly(methyl methacrylate) block and a hydrophilic poly[N,N-2-(dimethylamino)-ethyl methacrylate) block (PMMA- b -PDMAEMA), was synthesized. Polymeric quaternary ammonium with three different alkyl chain lengths (C 2 , C 4 , and C 8 ) were successfully introduced to obtain as q -PMMA- b -PDMAEMA. The q -PMMA- b -PDMAEMA in the nanofiber matrix was confirmed by C=O bands (1734 cm −1 ) in the Fourier transform infrared spectra. Nano-sized spherical protuberances were distributed on the surface as revealed by field emission scanning and transmission electron microscopies. The PVDF/GO/ q -PMMA- b -PDMAEMA@PVA nanofibers has superhydrophilic properties (water contact angle = 0–20°) and the pure water flux was generally improved by increasing the alkyl chain length. When introducing the longest alkyl chain (C 8,OBC ), the total fouling ratio was the lowest (49.99%) and the bacteria removal capacities after 60 min were the highest for both Escherichia coli (4.2 × 10 5 CFU/mg) and Staphylococcus aureus (6.1 × 10 5 CFU/mg) via growth inhibition and cytoplasmic membrane damage.

The aim of this review was to analyze/investigate the synthesis, properties, and applications of polyvinyl alcohol–halloysite nanotubes (PVA–HNT), and their nanocomposites. Different polymers with versatile properties are attractive because of their introduction and potential uses in many fields. Synthetic polymers, such as PVA, natural polymers like alginate, starch, chitosan, or any material with these components have prominent status as important and degradable materials with biocompatibility properties. These materials have been developed in the 1980s and are remarkable because of their recyclability and consideration of the natural continuation of their physical and chemical properties. The fabrication of PVA–HNT nanocomposites can be a potential way to address some of PVA’s limitations. Such nanocomposites have excellent mechanical properties and thermal stability. PVA–HNT nanocomposites have been reported earlier, but without proper HNT individualization and PVA modifications. The properties of PVA–HNT for medicinal and biomedical use are attracting an increasing amount of attention for medical applications, such as wound dressings, drug delivery, targeted-tissue transportation systems, and soft biomaterial implants. The demand for alternative polymeric medical devices has also increased substantially around the world. This paper reviews individualized HNT addition along with crosslinking of PVA for various biomedical applications that have been previously reported in literature, thereby showing the attainability, modification of characteristics, and goals underlying the blending process with PVA.

Polyvinyl alcohol (PVA) demonstrates chemical stability and biocompatibility and is widely used in biomedical applications. The porous bamboo charcoal has excellent toxin absorptivity and has been used in blood purification. In this study, bamboo charcoal nanoparticles (BCNPs) were acquired with nano-grinding technology. The PVA and PVA/BCNP nanocomposite membranes were prepared and characterized by the tensile test, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Results showed that the tensile strength and elongation of the swollen PVA membranes containing 1% BCNPs (PB1) were significantly greater than those of PVA and other PVA/BCNP composite membranes. In addition, the major absorption band of OH stretching in the IR spectra shifted from 3262 cm−1 for PVA membrane containing 1% BCNP to 3244 cm−1 for PVA membrane containing 20% BCNP. This blue shift might be attributed to the interaction between the PVA molecules and BCNPs. Moreover, the intensity of the XRD peaks in PVA was decreased with the increased BCNP content. The bioactivity of the nanocomposites was evaluated by immersion in the simulated body fluid (SBF) for seven days. The mineral deposition on PB5 was significantly more than that on the other samples. The mineral was identified as hydroxyapatite (HA) by XRD. These data suggest that the bioactivity of the composite hydrogel membranes was associated with the surface distribution of hydrophilic/hydrophobic components. The PVA/BCNP composite hydrogels may have potential applications in alveolar bone regeneration.

Ag nanoparticles were in-situ grown on the surface of MXene nanosheets to prepare thermally conductive hetero-structured MXene@Ag fillers. With polyvinyl alcohol (PVA) as the polymer matrix, thermally conductive MXene@Ag/PVA composite films were fabricated by the processes of solution blending, pouring, and evaporative self-assembly. With the same mass fraction, MXene@Ag-III (MXene/Ag, 2:1, w/w) presents more significant improvement in thermal conductivity coefficient (λ) than MXene@Ag, single MXene, Ag, and simply blending MXene/Ag. MXene@Ag-III/PVA composite films show dual functions of excellent thermal conductivity and electromagnetic interference (EMI) shielding. When the mass fraction of MXene@Ag-III is 60 wt.%, the in-plane λ (λ ∥ ), through-plane λ (λ ⊥ ), and EMI shielding effectiveness (EMI SE) are 3.72 and 0.41 W/(m·K), and 32 dB, which are increased by 3.1, 1.3, and 105.7 times than those of pure PVA film (0.91 and 0.18 W/(m·K), and 0.3 dB), respectively. The 60 wt.% MXene@Ag-III/PVA composite film also has satisfying mechanical and thermal properties, with Young’s modulus, glass transition temperature, and heat resistance index of 3.8 GPa, 58.5 and 175.3 °C, respectively.

Polyvinyl alcohol (PVA)-based hydrogels have attracted significant attention due to their excellent biocompatibility, tunable mechanical properties, and ability to form stable three-dimensional networks. This comprehensive review explores the recent advancements in PVA-based hydrogels, focusing on their unique properties, fabrication strategies, and multifunctional applications. Firstly, it discusses various facile synthesis techniques, including freeze/thaw cycles, chemical cross-linking, and enhancement strategies, which have led to enhanced mechanical strength, elasticity, and responsiveness to external stimuli. These improvements have expanded the applicability of PVA-based hydrogels in critical areas such as biomedical, environmental treatment, flexible electronics, civil engineering, as well as other emerging applications. Additionally, the integration of smart functionalities, such as self-healing capabilities and multi-responsiveness, is also examined. Despite progress, challenges remain, including optimizing mechanical stability under varying conditions and addressing potential toxicity of chemical cross-linkers. The review concludes by outlining future perspectives, emphasizing the potential of PVA-based hydrogels in emerging fields like regenerative medicine, environmental sustainability, and advanced manufacturing. It underscores the importance of interdisciplinary collaboration in realizing the full potential of these versatile materials to address pressing societal challenges.

Administration of drugs via the buccal route has attracted much attention in recent years. However, developing systems with satisfactory adhesion under wet conditions and adequate drug bioavailability still remains a challenge. Here, we propose a mussel-inspired mucoadhesive film. Ex vivo models show that this film can achieve strong adhesion to wet buccal tissues (up to 38.72 ± 10.94 kPa). We also demonstrate that the adhesion mechanism of this film relies on both physical association and covalent bonding between the film and mucus. Additionally, the film with incorporated polydopamine nanoparticles shows superior advantages for transport across the mucosal barrier, with improved drug bioavailability (~3.5-fold greater than observed with oral delivery) and therapeutic efficacy in oral mucositis models (~6.0-fold improvement in wound closure at day 5 compared with that observed with no treatment). We anticipate that this platform might aid the development of tissue adhesives and inspire the design of nanoparticle-based buccal delivery systems. Minimally invasive drug delivery is of wide interest and oral tissue is an attractive target for this. Here, the authors report on the creation of mussel-inspired films for retention on the wet oral tissue for the delivery of drugs by diffusion and transport though the mucosal tissue.

Multipotent self-renewing haematopoietic stem cells (HSCs) regenerate the adult blood system after transplantation 1 , which is a curative therapy for numerous diseases including immunodeficiencies and leukaemias 2 . Although substantial effort has been applied to identifying HSC maintenance factors through the characterization of the in vivo bone-marrow HSC microenvironment or niche 3 – 5 , stable ex vivo HSC expansion has previously been unattainable 6 , 7 . Here we describe the development of a defined, albumin-free culture system that supports the long-term ex vivo expansion of functional mouse HSCs. We used a systematic optimization approach, and found that high levels of thrombopoietin synergize with low levels of stem-cell factor and fibronectin to sustain HSC self-renewal. Serum albumin has long been recognized as a major source of biological contaminants in HSC cultures 8 ; we identify polyvinyl alcohol as a functionally superior replacement for serum albumin that is compatible with good manufacturing practice. These conditions afford between 236- and 899-fold expansions of functional HSCs over 1 month, although analysis of clonally derived cultures suggests that there is considerable heterogeneity in the self-renewal capacity of HSCs ex vivo. Using this system, HSC cultures that are derived from only 50 cells robustly engraft in recipient mice without the normal requirement for toxic pre-conditioning (for example, radiation), which may be relevant for HSC transplantation in humans. These findings therefore have important implications for both basic HSC research and clinical haematology. An albumin-free culture system for the long-term ex vivo expansion of mouse haematopoietic stem cells produces 236- to 899-fold expansion, and generates cultures that robustly engraft in recipient mice without toxic pre-conditioning.