Preparation and Performance of Antibacterial Polyvinyl Alcohol/Polyethylene Glycol/Chitosan Hydrogels Containing Silver Chloride Nanoparticles via One-step Method

Analysis of natural photocatalysts derived from spartina alterniflora with superior removal performance of pollutant

Spartina alterniflora, as an invasive alien species, has been studied in terms of its potential use in immobilization and synergistic photocatalysis against dye contaminants for the first time. Microscopic characterization and Fourier transform infrared (FTIR) spectroscopy results confirmed the presence of abundant 3D wormhole-like pore structures and active functional groups (-OH, -NH2, CO, Si-O-Si). Moreover, the existence of SiO2 was connected the metal oxides with polar groups, which could proceed entire reaction procedure subsequently. Transition metal oxides (such as Fe2O3, TiO2, MnO2 and NiO) contained in photocatalysts might effectively promote the organics decomposition by the visible light excitation. The highest dye removal efficiency of 92.03% could be reached with the addition of 0.02 g photocatalyst. The capture experiment confirmed that the h+ was the dominant active substance during the photocatalytic degradation process. Density functional theory (DFT) calculations verified that the functional groups (-COOH, -OH and -NH2) were exceptional adsorption sites for catalyst, and the calculated adsorption energy were all negative with the order of SRHH-NH2 (-2.712688 eV) < SRHH-OH (-2.075601 eV) < SRHH-COOH (-1.283141 eV), which confirmed that interface interaction effectively bound cationic dyes through the formation of hydrogen bonds at the catalysts-water interface, further accelerating the reaction rate of the entire photocatalytic reduction of dye molecules. Therefore, this work provides a feasible synthesis of natural photocatalysts using solid waste, which suggests excellent adsorption and photocatalysis properties for the treatment of organic industrial pollutant.

Photochromic biodegradable film based on polyvinyl alcohol modified with silver chloride nanoparticles and spirulina; investigation of physicochemical, antimicrobial and optical properties

In this study, biodegradable film was prepared from polyvinyl alcohol (PVA), Silver chloride (AgCl) and spirulina (Sp). Surface morphology, mechanical properties, antioxidant, antimicrobial, optical properties, etc. were investigated. The FTIR results confirmed the effect of AgCl and Sp on PVA structure. Sp increased the moisture content and solubility in water. The XRD results showed the semi-crystalline structure of PVA. AgCl nanoparticles activated the antibacterial property of the film against Escherichia coli and Staphylococcus aureus bacteria and Sp caused a strong increase in the antioxidant property of the film. Examining the light transmittance of films containing AgCl nanoparticles showed that the transmittance of films containing nanoparticles decreased with exposure to sunlight and ultraviolet light with increasing treatment time, which indicates the activation of the photochromic property of films containing AgCl in the presence of light. The results showed the suitable photochromic property of the PVA/AgCl films.

Progress in preparation and properties of chitosan-based hydrogels

Chitosan is a kind of natural polysaccharide biomass with the second highest content in nature after cellulose, which has good biological properties such as biocompatibility, biodegradability, hemostasis, mucosal adsorption, non-toxicity, and antibacterial properties. Therefore, hydrogels prepared from chitosan have the advantages of good hydrophilicity, unique three-dimensional network structure, and good biocompatibility, so they have received extensive attention and research in environmental testing, adsorption, medical materials, and catalytic supports. Compared with traditional polymer hydrogels, biomass chitosan-based hydrogels have advantages such as low toxicity, excellent biocompatibility, outstanding processability, and low cost. This paper reviews the preparation of various chitosan-based hydrogels using chitosan as raw material and their applications in the fields of medical materials, environmental detection, catalytic carriers, and adsorption. Some views and prospects are put forward for the future research and development of chitosan-based hydrogels, and it is believed that chitosan-based hydrogels will be able to obtain more valuable applications.

Antimicrobial and Mechanical Properties of Ag@Ti3C2Tx-Modified PVA Composite Hydrogels Enhanced with Quaternary Ammonium Chitosan

Polyvinyl alcohol (PVA) is a polymeric material with good biocompatibility, excellent hydrophilicity, and a large number of hydroxyl groups. However, due to its insufficient mechanical properties and poor inhibition of bacteria, it has a lack of applications in wound dressings, stent materials, and other fields. In this study, a simple method was used to prepare composite gel materials: Ag@MXene-HACC-PVA hydrogels with a double-network structure were prepared using an acetal reaction. Due to the double cross-linked interaction, the hydrogel has good mechanical properties and is resistant to swelling. The adhesion and bacterial inhibition were enhanced due to the addition of HACC. In addition, the strain sensing properties of this conductive hydrogel were stable, and the GF (specification factor) was 1.7617 at 40-90% strain. Therefore, the dual-network hydrogel with excellent sensing properties, adhesion properties, antibacterial properties, and cytocompatibility has potential applications in biomedical materials, especially as a tissue engineering repair material.

Balancing the antibacterial and osteogenic effects of double-layer TiO2 nanotubes loaded with silver nanoparticles for the osseointegration of implants

The improvement of Ag nanoparticles (AgNPs), in particular, loaded titania nanotubes, includes not only the antibacterial effect but also balancing the side effects from the antibacterial effect and osteogenesis properties, which can lead to an increased success rate of implants. Herein, based on the various needs of the graft to inhibit bacteria at different stages in vivo, we used a special osteogenic honeycomb-like "large tube over small tube" double-layered nanotube structure and created ultra-small-sized silver nanoparticles uniformly loaded on the surface and the interior of double-layer nanotubes by an optimized sputter coating method to ensure the time-dependent controllable release of antibacterial Ag ions from grafts and achieve the balance of the antibacterial effect and osteogenesis properties. The release of Ag⁺ from DNT-Ag8 was determined by inductively coupled plasma spectrometry. The release rate of Ag was slow; it was 30% on the first day and plateaued by the 19th day. Porphyromonas gingivalis adhesion and live bacteria were less abundant on the surface of DNT-Ag8, reaching an antibacterial efficiency of 55.6% in vitro. DNT-Ag8 shows a significantly higher antibacterial effect in a rat model infected with Staphylococcus aureus. An in vitro study demonstrated that DNT-Ag8 had no adverse effects on the adhesion, viability, proliferation, ALP staining, or activity assays of rat BMSCs. In contrast, it increased the expression of osteogenic genes. In vivo, DNT-Ag8 promoted bone-implant osseointegration in a beagle mandibular tooth loss model. This study demonstrated that the uniform loading of small-diameter silver nanoparticles using a honeycomb bilayer nanotube template structure is a promising method for modifying titanium surfaces to improve both bacteriostasis and osseointegration.

Nanomaterials supported by polymers for tissue engineering applications: A review

In the biomedical sciences, particularly in wound healing, tissue engineering, and regenerative medicine, the development of natural-based biomaterials as a carrier has revealed a wide range of advantages. Tissue engineering is one of the therapeutic approaches used to replace damaged tissue. Polymers have received a lot of attention for their beneficial interactions with cells, but they have some drawbacks, such as poor mechanical properties. Due to their relatively large surface area, nanoparticles can cause significant changes in polymers and improve their mechanical properties. The nanoparticles incorporated into biomaterial scaffolds have been associated with positive effects on cell adhesion, viability, proliferation, and migration in the majority of studies. This review paper discusses recent applications of polymer-nanoparticle composites in the development of tissue engineering scaffolds, as well as the effects of these nanomaterials in the fields of cardiovascular, neural, bone, and skin tissue engineering.

An excellent antibacterial and high self-adhesive hydrogel can promote wound fully healing driven by its shrinkage under NIR

The lacks of antibacterial properties, low adhesion and delayed wound healing of the hydrogel wound dressings limit their applications in wound treatment. To resolve these, a novel hydrogel composed of polydopamine (PDA), Ag and graphene oxide (GO) is fabricated for wound dressing via the chemical crosslinking of N-isopropylacrylamide (NIPAM) and N,N'-methylene bisacrylamide (BIS). The prepared hydrogel containing PDA@Ag5GO1 (Ag5GO1 denotes the mass ratio between Ag and GO is 5:1) exhibits effective antibacterial properties and high inhibition rate against E. coli and S. aureus. It shows high adhesion ability to various substrate materials, implying a simpler method to the wound obtained by self-fixing rather than suturing. More important, it can produce strong contractility under the irradiation of near-infrared light (NIR), exerting a centripetal force that helps accelerate wound healing. Thus, the hydrogel containing a high concentration PDA@Ag5GO1 irradiated by NIR can completely repair the wound defect (1.0 × 1.0 cm²) within 15 days, the wound healing rate can reach 100%, which was far higher than other groups. Taken together, the new hydrogel with excellent antibacterial, high adhesion and strong contractility will subvert the traditional treatment methods on wound defect, extending its new application range in wound dressing.

Dual Cross-Linked Chitosan/PVA Hydrogels Containing Silver Nanoparticles with Antimicrobial Properties

Stable chitosan/PVA-based hydrogels were obtained by combining covalent and physical cross-linking methods. As covalent cross-linkers, epoxy agents with different chain lengths were used, while freeze-thaw cycles were applied for additional physical cross-linking. The chemical structure of the hydrogel was examined by FTIR spectroscopy whereas the morphology was analyzed by SEM, showing well-defined pores with dimensions of around 50 μm in diameter. It was proved that gel fraction and the network morphology were deeply influenced by the synthesis conditions. Chitosan/PVA hydrogel showed a relative high swelling rate, reaching equilibrium in the first hour. The values obtained for the elastic modulus were relatively low (3-30 kPa); as a result, these hydrogels are soft and very flexible, and are ideal candidates for medical applications as wound or oral dressings. In addition, the natural antimicrobial activity of chitosan was enhanced by in situ generation of silver nanoparticles (AgNPs) under UV irradiation. The total amount of Ag from hydrogel was determined by elemental analyses and its crystalline state was confirmed by XRD. The CS/PVA hydrogels entrapped with AgNPs exhibited high inhibitory activity against S. aureus and K. pneumonia. The vitality tests confirmed the lack of cytotoxicity of CS/PVA hydrogels without and with AgNPs.

Unilateral Silver-Loaded Silk Fibroin Difunctional Membranes as Antibacterial Wound Dressings

Silk fibroin (SF) has been widely used as wound dressings due to its good biocompatibility. To enhance the antibacterial properties of the dressings, silver (Ag) is often added. However, an overdose of Ag may cause cytotoxicity and inhibit wound healing. Therefore, this study aimed to develop a two-layered membrane to reduce cytotoxicity while maintaining the antibacterial properties of Ag through a simplified layer-by-layer technique. The membranes comprised an Ag-rich SF layer (Ag-SF) and a pure SF layer. The unilateral Ag-loaded membranes showed efficient antibacterial properties at doses above 0.06 mg/mL Ag, and the antibacterial properties were comparable on both sides. In contrast, the SF sides of the membranes showed lower cytotoxicity than the Ag-SF sides of the membranes. Further studies on the thickness ratio of Ag-SF/SF layers revealed that Ag0.12-SF/SF membranes with a ratio of 1:3 had high cytocompatibility on the SF sides while holding a strong antibacterial property. Besides, the SF sides of the Ag0.12-SF/SF1:3 membranes promoted the expression levels of collagen I and transforming growth factor-β mRNA in human foreskin fibroblasts. The SF sides of the Ag0.12-SF/SF1:3 membranes significantly promoted the healing of infected wounds in vivo. Therefore, unilateral loading with the simplified layer-by-layer preparation technique provided an effective method to balance the cytotoxicity and the antibacterial property of Ag-loaded materials and thus form a broader therapeutic window for Ag applications. The unilateral Ag-loaded silk fibroin difunctional membranes have the potential to be further preclinically explored as wound dressings.

Applications of Absorbent Polymers for Sustainable Plant Protection and Crop Yield

Natural strategies for protecting the environment as well as plant, animal and human health is considered one of the main goals of developed countries. Recently, the use of absorbent polymers and hydrogel in agriculture has demonstrated several benefits for soil amendments, saving water content, reducing the consumption of soil nutrients, minimizing the negative impacts of dehydration and moisture stress in crops and controlling several phytopathogens. The seed-coating technology for establishing the crops is a recent common practice used for improving seed protection and enhancing plant growth. Coating materials include absorbent polymers and hydrogels based on growth regulators, pesticides, fertilizers and antagonist microorganisms. The current review has highlighted the importance of different types of superabsorbent polymers and hydrogels in an integrated strategy to protect seeds, plants and soil in a balanced manner to preserve the ecosystem.

Synthesis of nanocomposite hydrogel based carboxymethyl starch/polyvinyl alcohol/nanosilver for biomedical materials

Treatment of infections using wound dressing integrated with multiple functions such as antibacterial activity, non-toxicity, and good mechanical properties has attracted much attention. In this study, carboxymethyl starch/polyvinyl alcohol/citric acid (CMS/PVA/CA) hydrogels containing silver nanoparticles (AgNPs) were prepared. The CMS, PVA and CA were used as polymer matrix and bio-based reducing agents for green synthesis of AgNPs. Silver nitrate (AgNO₃) concentrations of 50, 100, and 150 mM were used to obtain nanocomposite hydrogels containing different AgNPs concentrations (AgNPs-50, AgNPs-100 and AgNPs-150, respectively). The minimum inhibitory concentration against E. coli and S. aureus was observed in CMS/PVA/CA hydrogels containing AgNPs-50. Uniform dispersion of AgNPs-100 in the hydrogel provided the highest storage modulus at 56.4 kPa. AgNPs-loaded hydrogels showed low toxicity to human fibroblast cells indicating good biocompatibility. Incorporation of AgNPs demonstrated an enhancement in antibacterial properties and overall mechanical properties, which makes these nanocomposite hydrogels attractive as novel wound dressing materials.