Antibacterial polyvinyl alcohol/bacterial cellulose/nano-silver hydrogels that effectively promote wound healing

Hybrid Ag nanoparticles/polyoxometalate-polydopamine nano-flowers loaded chitosan/gelatin hydrogel scaffolds with synergistic photothermal/chemodynamic/Ag+ anti-bacterial action for accelerated wound healing

Bacterial infections significantly slow the wound healing process, thus severely threatening human health. Furthermore, traditional antibiotics may promote the development of multidrug-resistant bacteria. Therefore, developing novel bactericides and therapeutic strategies for bacterial infections is important to enhance wound healing. Herein, a three-in-one bactericidal flower-like nanocomposite was assembled using Ag nanoparticles/phosphotungstic acid-polydopamine nano-flowers (AgNPs/POM-PDA). The nanocomposite exhibited photothermal therapy (PTT) when exposed to NIR light via photothermal conversion by PDA. The resultant photothermal effect accelerated and controlled the Ag⁺ released from AgNPs. The chemodynamic therapy (CDT) was obtained via POM catalytic Fenton-like reaction. The combined PTT/CDT/Ag⁺ treatment achieved excellent synergistic anti-bacterial activity against both gram-negative E. coli and gram-positive S. aureus. A multifunctional wound dressing was then obtained by embedding the AgNPs/POM-PDA flower-like nanocomposite into the chitosan (CS)/gelatin (GE) biocomposite hydrogel. The synergy of AgNPs/POM-PDA nanocomposites and CS/GE hydrogel remarkably accelerated wound healing in vivo due to the excellent biocompatibility, hydroabsorptivity, and breathability of the hydrogel. In this study, a multifunctional agent was developed to synergistically combat bacterial infections and accelerate wound healing.

Polyvinyl alcohol/carboxymethyl chitosan hydrogel loaded with silver nanoparticles exhibited antibacterial and self-healing properties

Hydrogel materials are gradually increasing research in biological aspects due to their unique properties. In order to prepare hydrogels with the potential to be used in clinical wound therapy, the authors prepared a bifunctional hydrogel with antibacterial and self-healing properties. The hydrogel was composed of borax cross-linked polyvinyl alcohol (PVA) and carboxymethyl chitosan (CMCS), which realizes self-healing between polymers through hydrogen bonds and borate ester bonds. The double cross-linking of hydrogen bonds and borate ester bonds also endows the hydrogel with better mechanical properties (toughness and tensile stress can reach 22.30 MJ/m³ and 70.35 KPa, respectively). On this basis, adding highly stable silver nanoparticles (AgNPs) to the hydrogel can effectively inhibit the growth of E. coli and S. aureus. This idea provides the possibility for the application of hydrogels in the process of biological wound healing.

Recent Progress in Electrospun Polyacrylonitrile Nanofiber-Based Wound Dressing

Bleeding control plays a very important role in worldwide healthcare, which also promotes research and development of wound dressings. The wound healing process involves four stages of hemostasis, inflammation, proliferation and remodeling, which is a complex process, and wound dressings play a huge role in it. Electrospinning technology is simple to operate. Electrospun nanofibers have a high specific surface area, high porosity, high oxygen permeability, and excellent mechanical properties, which show great utilization value in the manufacture of wound dressings. As one of the most popular reactive and functional synthetic polymers, polyacrylonitrile (PAN) is frequently explored to create nanofibers for a wide variety of applications. In recent years, researchers have invested in the application of PAN nanofibers in wound dressings. Research on spun nanofibers is reviewed, and future development directions and prospects of electrospun PAN nanofibers for wound dressings are proposed.

Chitosan Biguanidine/PVP Antibacterial Coatings for Perishable Fruits

World hunger is on the rise, yet one-third of food is wasted. It is necessary to develop an effective food preservation method to reduce food waste. This article reports a composite film based on chitosan biguanidine hydrochloride(CBg) and poly (N-vinyl-2-pyrrolidone)(PVP) that can be used as a conformal coating for fresh produce. Due to the strong positive charge of CBg, the film has excellent antibacterial properties. Owing to the hydrogen bonds between CBg and PVP, the film has good flexibility and mechanical properties. In addition, the coating is washable, transparent, and can reduce the evaporation of water. The above characteristics mean the film has broad application prospects in the field of food preservation.

Novel Technologies in Chronic Wound Care

In Israel, 20% of wounds do not progress to full healing under treatment with conservative technologies of which 1 to 2% are eventually defined as chronic wounds. Chronic wounds are a complex health burden for patients and pose considerable therapeutic and budgetary burden on health systems. The causes of chronic wounds include systemic and local factors. Initial treatment involves the usual therapeutic means, but as healing does not progress, more advanced therapeutic technologies are used. Undoubtedly, advanced means, such as negative pressure systems, and advanced technologies, such as oxygen systems and micrografts, have vastly improved the treatment of chronic wounds. Our service specializes in treating ulcers and difficult-to-heal wounds while providing a multiprofessional medical response. Herein, we present our experience and protocols in treating chronic wounds using a variety of advanced dressings and technologies.

Novel functionalized selenium nanowires as antibiotic adjuvants in multiple ways to overcome drug resistance of multidrug-resistant bacteria

Methicillin-resistant Staphylococcus (MRS) is a multi-drug resistant bacteria that pose a serious threat to human health. Antibacterial nanomaterials are becoming a promising antibiotic substitute or antibiotic adjuvants. In this work, selenium nanowires were modified with nano‑silver (Ag NPs) with antibacterial activity and [Ru(bpy)₂dppz]²⁺ with fluorescent labeling of DNA (SRA), and the antibacterial activity, antibacterial mechanism and biological toxicity of SRA synergistic antibiotics were studied. In vitro, antibacterial results show that SRA (12 μg/mL) improves the antibacterial activity of various antibiotics against resistant bacteria and significantly slows the development of bacterial resistance to antibiotics. Studies on antibacterial mechanisms have shown that SRA synergistic antibiotics destroy drug-resistant bacteria through a combination of physical (physical damage) and chemical pathways (destruction of biofilm, membrane depolarization, cell membrane destruction, adenosine triphosphate consumption and reactive oxygen species production). Transcriptomics analysis found that SRA affects bacterial activity by affecting bacterial biosynthesis, ATP synthesis and biofilm formation. Furthermore, SRA synergistic antibiotics can accelerate wound healing of bacterial infection by reducing the inflammatory response. The toxicity evaluation results show that SRA has extremely low cellular and in vivo toxicity. SRA has the potential of clinical application as multiple antibiotic adjuvants to deal with resistant bacterial infections.

Superabsorbent cellulose-based hydrogels cross-liked with borax

Cellulose, the most abundant biopolymer on Earth, has been widely attracted owing to availability, intoxicity, and biodegradability. Environmentally friendly hydrogels were successfully prepared from water hyacinth-extracted cellulose using a dissolution approach with sodium hydroxide and urea, and sodium tetraborate decahydrate (borax) was used to generate cross-linking between hydroxyl groups of cellulose chains. The incorporation of borax could provide the superabsorbent feature into the cellulose hydrogels. The uncross-linked cellulose hydrogels had a swelling ratio of 325%, while the swelling ratio of the cross-linked hydrogels could achieve ~ 900%. With increasing borax concentrations, gel fraction of the cross-linked hydrogels increased considerably. Borax also formed char on cellulose surfaces and generated water with direct contact with flame, resulting in flame ignition and propagation delay. Moreover, the cross-linked cellulose-based hydrogels showed antibacterial activity for gram-positive bacteria (S. aureus). The superabsorbent cross-linked cellulose-based hydrogels prepared in this work could possibly be used for wound dressing, agricultural, and flame retardant coating applications.

How Effective are Nano-Based Dressings in Diabetic Wound Healing? A Comprehensive Review of Literature

Chronic wound caused by diabetes is an important cause of disability and seriously affects the quality of life of patients. Therefore, it is of great clinical significance to develop a wound dressing that can accelerate the healing of diabetic wounds. Nanoparticles have great advantages in promoting diabetic wound healing due to their antibacterial properties, low cytotoxicity, good biocompatibility and drug delivery ability. Adding nanoparticles to the dressing matrix and using nanoparticles to deliver drugs and cytokines to promote wound healing has proven to be effective. This review will focus on the effects of diabetes on wound healing, introduce the properties, preparation methods and action mechanism of nanoparticles in wound healing, and describe the effects and application status of various nanoparticle-loaded dressings in diabetes-related chronic wound healing.

Functionalization and Antibacterial Applications of Cellulose-Based Composite Hydrogels

Pathogens, especially drug-resistant pathogens caused by the abuse of antibiotics, have become a major threat to human health and public health safety. The exploitation and application of new antibacterial agents is extremely urgent. As a natural biopolymer, cellulose has recently attracted much attention due to its excellent hydrophilicity, economy, biocompatibility, and biodegradability. In particular, the preparation of cellulose-based hydrogels with excellent structure and properties from cellulose and its derivatives has received increasing attention thanks to the existence of abundant hydrophilic functional groups (such as hydroxyl, carboxy, and aldehyde groups) within cellulose and its derivatives. The cellulose-based hydrogels have broad application prospects in antibacterial-related biomedical fields. The latest advances of preparation and antibacterial application of cellulose-based hydrogels has been reviewed, with a focus on the antibacterial applications of composite hydrogels formed from cellulose and metal nanoparticles; metal oxide nanoparticles; antibiotics; polymers; and plant extracts. In addition, the antibacterial mechanism and antibacterial characteristics of different cellulose-based antibacterial hydrogels were also summarized. Furthermore, the prospects and challenges of cellulose-based antibacterial hydrogels in biomedical applications were also discussed.

Alginate-enabled green synthesis of S/Ag1.93S nanoparticles, their photothermal property and in-vitro assessment of their anti-skin-cancer effects augmented by a NIR laser

We report herein the design and synthesis of colloidally-stable S/Ag_1.93S nanoparticles, their photothermal conversion properties and in vitro cytotoxicity toward A431 skin cancer cells under the excitation of a minimally-invasive 980 nm near-infrared (NIR) laser. Micron-sized S particles were first synthesized via acidifying Na₂S₂O₃ using biocompatible sodium alginate as a surfactant. In the presence of AgNO₃ and under rapid microwave-induced heating, alginate reduced AgNO₃ to nascent Ag which reacted with molten S in situ to S/Ag_1.93S nanoparticles. The nanoparticles were characterized using a combination of X-ray diffraction, electron microscopies, elemental analysis, zeta-potential analysis and UV-VIS-NIR spectroscopy. The average particles size was controlled between 40 and 60 nm by fixing the mole ratio of Ag⁺:S₂O₃^2-. When excited by a 980 nm laser, S/Ag_1.93S nanoparticles (~40 nm) produced with the least amount of AgNO₃ exhibited a respectable photothermal conversion efficiency of circa 62% with the test aqueous solution heated to a hyperthermia-inducing 52 °C in 15 min. At 0.7 W/cm², the viability of A431 skin cancer cells incubated with 7.0 ± 0.2 μg/mL of S/Ag_1.93S nanoparticles reduced to 14 ± 0.6%, while an A431 cell control maintained an 80% cell viability. These results suggested that S/Ag_1.93S nanoparticles may have good potential in reducing metastatic skin carcinoma.

The construction of a seaweed-based antibacterial membrane loaded with nano-silver based on the formation of a dynamic united dual network structure

A nano-silver based antibacterial membrane was obtained through a united dual network structure.

Effect of bacterial cellulose nanofibers incorporation on acid-induced casein gels: microstructures and rheological properties

In this study, the effect of bacterial cellulose nanofibers (BCNF) incorporation on the structural and rheological properties of casein gels was investigated, where the mixed BCNF and casein gels were prepared by adding gluconic acid δ-lactone (GDL) to acidify the mixed polymer solutions at 3.0% casein concentration (w/v) and varying BCNF concentrations (0–0.5%, w/v). By changing the addition amount of GDL, the mechanical and structural properties of the mixed gels were studied at above, near and below the electric point (pI) of the casein. At pH above the pI of the casein, the introduction of BCNF initially increased the gel strength, but further addition of BCNF weakened the mixed gels. At near and below the pI of the casein, the incorporation of BCNF continuously increased the gel strength. Besides, all gels showed good structural homogeneity, without macroscopic phase separation occurring, which indicated good compatibility of BCNF with the casein gels.

A Novel Conductive Antibacterial Nanocomposite Hydrogel Dressing for Healing of Severely Infected Wounds

Wound infections are serious medical complications that can endanger human health. Latest researches show that conductive composite materials may make endogenous/exogenous electrical stimulation more effective, guide/comb cell migration to the wound, and subsequently promote wound healing. To accelerate infected wound healing, a novel medical silver nanoparticle-doped conductive polymer-based hydrogel system (Ag NPs/CPH) dressing with good conductivity, biocompatibility, and mechanical and antibacterial properties was fabricated. For the hydrogel dressing, Ag NPs/CPH, polyvinyl alcohol (PVA), and gelatin were used as the host matrix materials, and phytic acid (PA) was used as the cross-linking agent to introduce conductive polyaniline into the matrix, with antibacterial Ag NPs loaded via impregnation. After a series of analyses, the material containing 5 wt% of PVA by concentration, 1.5 wt% gelatin, 600 μL of AN reactive volume, and 600 μL of PA reactive volume was chosen for Ag NPs/CPH preparation. XPS and FTIR analysis had been further used to characterize the composition of the prepared Ag NPs/CPH. The test on the swelling property showed that the hydrogels had abundant pores with good water absorption (≈140% within 12 h). They can be loaded and continuously release Ag NPs. Thus, the prepared Ag NPs/CPH showed excellent antibacterial property with increasing duration of immersion of Ag NPs. Additionally, to evaluate in vivo safety, CCK-8 experiments of HaCat, LO2 and 293T cells were treated with different concentrations of the Ag NPs/CPH hydrogel soaking solution. The experimental results showed the Ag NPs/CPH had no significant inhibitory effect on any of the cells. Finally, an innovative infection and inflammation model was designed to evaluate the prepared Ag NPs/CPH hydrogel dressing for the treatment of severely infected wounds. The results showed that even when infected with bacteria for long periods of time (more than 20 h), the proposed conductive antibacterial hydrogel could treat severely infected wounds.

Preparation of Electrospun Polyvinyl Alcohol/Nanocellulose Composite Film and Evaluation of Its Biomedical Performance

Using polyvinyl alcohol (PVA) and nanocellulose (NC) as raw materials, PVA/NC nanofiber membranes were prepared by electrospinning. The hydrogen bonding, crystalline properties and microscopic appearance of PVA/NC membranes with different NC contents were characterized. The mechanical properties, liquid absorption and cytotoxicity of the nanofiber membrane were evaluated. The results show that the free hydroxyl group of the PVA/NC nanofiber membranes have a maximum value of 9% at a mass fraction of 6% NC. The crystallinity of the PVA/NC nanofiber membranes and the average diameter of the nanofibers decreased and then increased as the NC content increased, with a minimum value of 38.23% and 272.03 nm, respectively, at 6% NC content. At this time, the contact angle was the smallest. The maximum strength of the PVA/NC nanofiber membranes is 75.8% higher than that of the PVA membrane at 2% NC content. With increasing NC content, the absorption of water, PBS sustained-release suspensions and artificial blood by PVA/NC nanofiber membranes increases. Cytotoxicity tests have shown that PVA/NC nanofiber membranes are non-toxic, have good cytocompatibility and are expected to be used in the field of medical dressings.

Ascorbic acid-loaded polyvinyl alcohol/cellulose nanofibril hydrogels as precursors for 3D printed materials

We proposed a simple method to process hydrogels containing polyvinyl alcohol and cellulose nanofibrils (PVA/CNF) to prepare volumetric architectures by direct ink writing (DIW). The presence of CNF in the aqueous PVA suspensions conferred rheology profiles that were suitable for extrusion and solidification in pre-designed shapes. The viscoelastic behavior of the hybrid inks enabled precise control on processability and shape retention, for instance, as demonstrated in multilayered lattice structures of high fidelity. After lyophilization, the obtained 3D-printed hydrogels presented a very high porosity, with open and interconnected pores, allowing a high-water uptake capacity (up to 1600%). The mechanical strength of the composite 3D-printed materials matched those of soft tissues, opening opportunities for skin applications. As such, drug-loaded samples revealed a controlled and efficient delivery of an antioxidant (ascorbic acid) in PBS buffer media at 23 °C (~80% for 8 h). Altogether, PVA/CNF hydrogels were introduced as suitable precursors of 3D-lattice geometries with excellent physical and mechanical characteristics.

Chloramphenicol Loaded Sponges Based on PVA/Nanocellulose Nanocomposites for Topical Wound Delivery

In the present study, polymer sponges based on poly(vinyl alcohol) (PVA) were prepared for the topical wound administration of chloramphenicol (CHL), an antibiotic widely used to treat bacterial infections. Nanocellulose fibrils (CNF) were homogenously dispersed in PVA sponges in three different ratios (2.5, 5, and 10 wt %) to improve the mechanical properties of neat PVA sponges. Infrared spectroscopy showed hydrogen bond formation between CNF and PVA, while scanning electron microscopy photos verified the successful dispersion of CNF to PVA sponges. The addition of CNF successfully enhanced the mechanical properties of PVA sponges, exhibiting higher compressive strength as the content of CNF increased. The PVA sponge containing 10 wt % CNF, due to its higher compression strength, was further studied as a matrix for CHL delivery in 10, 20, and 30 wt % concentration of the drug. X-ray diffraction showed that CHL was encapsulated in an amorphous state in the 10 and 20 wt % samples, while some crystallinity was observed in the 30 wt % ratio. In vitro dissolution studies showed enhanced CHL solubility after its incorporation in PVA/10 wt % CNF sponges. Release profiles showed a controlled release lasting three days for the sample containing 10 wt % CHL and 1.5 days for the other two samples. According to modelling, the release is driven by a pseudo-Fickian diffusion.

Development of dual crosslinked mumio-based hydrogel dressing for wound healing application: Physico-chemistry and antimicrobial activity

In this study, an antimicrobial mumio-based hydrogel dressing was developed for wound healing application. The mechanism of gel formation was achieved via a double crosslink network formation between gelatin (GT) and polyvinyl alcohol (PVA) using polyethylene glycol diglycidyl ether (PEGDE) and borax as crosslinking agents. To enhance the mechanical integrity of the hydrogel matrix, bacterial cellulose (BC) was integrated into the GT-PVA hydrogel to produce a composite gel dressing. The obtained hydrogel was characterized by FTIR, SEM, TGA, and XRD. Gel fraction, in vitro swelling and degradation as well as compressive modulus properties of the gel dressing were investigated as a function of change in PVA and BC ratios. By increasing the ratios of PVA and BC, the composite dressing showed lower swelling but higher mechanical strength. Comparing to other formulations, the gel with 4 %w/v PVA and 1 %w/v BC demonstrated to be most suitable in terms of stability and mechanical properties. In vitro cell cytotoxicity by MTT assay on human alveolar basal epithelial (A549) cell lines validated the gels as non-toxic. In addition, the mumio-based gel was compared to other formulations containing different bioactive agents of beeswax and cinnamon oil, which were tested for microbial growth inhibition effects against different bacteria (S. aureus and K. pneumoniae) and fungi (C. albicans and A. niger) strains. Results suggested that the gel dressing containing combinations of mumio, beeswax and cinnamon oil possess promising future in the inhibition of microbial infection supporting its application as a suitable dressing for wound healing.