Gamma irradiation synthesis and characterization of AgNP/gelatin/PVA hydrogels for antibacterial wound dressings

Controllable Preparation and Research Progress of Photosensitive Antibacterial Complex Hydrogels

Hydrogels are materials consisting of a network of hydrophilic polymers. Due to their good biocompatibility and hydrophilicity, they are widely used in biomedicine, food safety, environmental protection, agriculture, and other fields. This paper summarizes the typical complex materials of photocatalysts, photosensitizers, and hydrogels, as week as their antibacterial activities and the basic mechanisms of photothermal and photodynamic effects. In addition, the application of hydrogel-based photoresponsive materials in microbial inactivation is discussed, including the challenges faced in their application. The advantages of photosensitive antibacterial complex hydrogels are highlighted, and their application and research progress in various fields are introduced in detail.

A nanofiber-hydrogel composite from green synthesized AgNPs embedded to PEBAX/PVA hydrogel and PA/Pistacia atlantica gum nanofiber for wound dressing

A polyamide/Pistacia atlantica (P.a) gum nanofiber, fabricated by electrospinning method, was coated on a layer of PEBAX/PVA hydrogel embedded with green synthesized Ag nanoparticles (AgNPs) and the prepared nanofiber-hydrogel composite was assessed for wound dressing application. The AgNPs were characterized using ultraviolet-visible (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zeta potential analysis. The PEBAX/PVA/Ag hydrogel, prepared using solution casting method, displayed strong mechanical properties as Young's modulus and the elongation at break for the hydrogel containing AgNPs increased by 12 % and 96 %, respectively. The PEBAX/PVA/Ag hydrogel showed a high antimicrobial activity towards the E. coli (22.8 mm) with no cytotoxicity. The effect of adding the P.a gum on the properties of polyamide nanofiber was investigated using FTIR, SEM, and tensile tests. Samples were assessed by swelling, degradation, and water vapor transfer measurements. Very fine and continuous fibers with average diameters of ≤200 nm were observed by SEM analysis due to the addition of the P.a gum. The result of tensile test indicated that the addition of P.a gum improves the mechanical properties of nanofibers. The physical properties and biocompatibility of the two layers were shown to be complementary when combined.

Antibacterial Hydrogel Sheet Dressings Composed of Poly(vinyl alcohol) and Silver Nanoparticles by Electron Beam Irradiation

Advanced wound dressings that can deliver potent antibacterial action are still much in need, especially for treating wound infections caused by drug-resistant bacteria. In this research, we utilized electron beam (EB) irradiation to develop antibacterial hydrogel sheet dressings from poly(vinyl alcohol) (PVA) and silver nanoparticles (AgNPs) in a two-step processing and evaluated their bactericidal efficacy, as well as the AgNP release. The effect of the irradiation dose on the swelling, gel fraction, network parameters, and mechanical properties of the hydrogels was first determined to establish the optimal doses for the two-step processing. The prototypic hydrogel sheets were then formed in the first EB irradiation and served as a matrix for the AgNP synthesis by the reduction of the silver nitrate precursors during the second EB irradiation. The diffusion assay showed that the minimal inhibition concentration (MIC) of the AgNP-load hydrogels was 0.25 and 0.5 mg/cm2 against Escherichia coli and Staphylococcus aureus, respectively. At these MIC levels, the released AgNPs increased sharply before reaching the maximum, ~950 and 1800 ppb, at 24 h as analyzed by atomic absorption. Therefore, we successfully demonstrated that this two-step processing by EB irradiation provides a convenient platform to fabricate AgNP-loaded hydrogel dressings that can be further developed for wound healing.

State of the Art of Hydrogel Wound Dressings Developed by Ionizing Radiation

The development of an ideal hydrogel wound dressing with excellent characteristics is currently a significant demand in wound therapy. The ideal hydrogel wound dressing must provide a moist environment between the wound and the dressing, promote wound healing, absorb excess exudate and toxins, be completely sterile, and not adhere to the wound. The evolution and current status of research on hydrogel wound dressings obtained exclusively through production by ionizing radiation are discussed in this paper review, along with the preparation methods, properties, standard characterization techniques, and their applications in wound dressing. First, we described the methods for synthesizing hydrogel wound dressings with ionizing radiation. Then, standard methods of characterization of hydrogel wound dressings such as gel fraction, swelling degree, sol-gel analysis, rheological properties, morphology, moisture retention capability, and water vapor transmission rate have been investigated. In the end, specific attention was paid to the drug release, antibacterial performance, and cytotoxicity of hydrogels. Moreover, the application of hydrogel in regenerative medicine as wound healing dressing was covered.

Electron Beam Irradiation Cross-Linked Hydrogel Patches Loaded with Red Onion Peel Extract for Transdermal Drug Delivery: Formulation, Characterization, Cytocompatibility, and Skin Permeation

The use of bioactive molecules derived from medicinal plants in wound healing has recently attracted considerable attention in both research and public interest. In this work, we demonstrated the first attempt to incorporate the extract from Thai red onion skins in hydrogel patches intended for transdermal delivery. The red onion skin extract (ROSE) was first prepared and evaluated for cytotoxicity by MTT assay with both L929 and human dermal fibroblast cells. Hydrogel patches with porous microstructure and high water content were fabricated from polyvinyl alcohol (PVA) by electron beam irradiation and characterized for their physical, mechanical, morphological, and cytocompatible properties prior to the loading of ROSE. After decontamination by electron beam irradiation, the in vitro release profile exhibited the burst release of extract from ROSE-coated hydrogel patches within 5 h, followed by the sustained release up to 48 h. Finally, evaluation of skin permeation using Franz cell setup with a newborn pig skin model showed that the permeation of ROSE from the hydrogel patch increased with time and reached the maximum of 262 µg/cm², which was well below the cytotoxicity threshold, at 24 h. These results demonstrated that our ROSE-coated hydrogel patches could potentially be used in transdermal delivery.

Injectable Crosslinked Genipin Hybrid Gelatin-PVA Hydrogels for Future Use as Bioinks in Expediting Cutaneous Healing Capacity: Physicochemical Characterisation and Cytotoxicity Evaluation

The irregular shape and depth of wounds could be the major hurdles in wound healing for the common three-dimensional foam, sheet, or film treatment design. The injectable hydrogel is a splendid alternate technique to enhance healing efficiency post-implantation via injectable or 3D-bioprinting technologies. The authentic combination of natural and synthetic polymers could potentially enhance the injectability and biocompatibility properties. Thus, the purpose of this study was to characterise a hybrid gelatin−PVA hydrogel crosslinked with genipin (GNP; natural crosslinker). In brief, gelatin (GE) and PVA were prepared in various concentrations (w/v): GE, GPVA3 (3% PVA), and GPVA5 (5% PVA), followed by a 0.1% (w/v) genipin (GNP) crosslink, to achieve polymerisation in three minutes. The physicochemical and biocompatibility properties were further evaluated. GPVA3_GNP and GPVA5_GNP with GNP demonstrated excellent physicochemical properties compared to GE_GNP and non-crosslinked hydrogels. GPVA5_GNP significantly displayed the optimum swelling ratio (621.1 ± 93.18%) and excellent hydrophilicity (38.51 ± 2.58°). In addition, GPVA5_GNP showed an optimum biodegradation rate (0.02 ± 0.005 mg/h) and the highest mechanical strength with the highest compression modulus (2.14 ± 0.06 MPa). In addition, the surface and cross-sectional view for scanning electron microscopy (SEM) displayed that all of the GPVA hydrogels have optimum average pore sizes (100−199 μm) with interconnected pores. There were no substantial changes in chemical analysis, including FTIR, XRD, and EDX, after PVA and GNP intervention. Furthermore, GPVA hydrogels influenced the cell biocompatibility, which successfully indicated >85% of cell viability. In conclusion, gelatin−PVA hydrogels crosslinked with GNP were proven to have excellent physicochemical, mechanical, and biocompatibility properties, as required for potential bioinks for chronic wound healing.

In situ synthesis of Ag NPs in the galactomannan based biodegradable composite for the development of active packaging films

The application of plastics in the food and agriculture industries as packaging materials is immense. However, the damage caused to the environment by accumulating such non-biodegradable plastics has led to the development of better alternatives. This has caused an increase in the use of synthetic polymers and proteins for the production of biodegradable films as an alternative to packaging plastics. In this study, a novel approach for the fabrication of homogenous and biodegradable films using PVA/galactomannan/gelatin (PGG) composite has been developed. The in-situ synthesis of silver nanoparticles (Ag NPs) was attained by hydrothermal reduction. The formation of Ag NPs within the PGG composite imparted substantial antimicrobial properties to the films. The optical properties of Ag NPs-PGG composite and its films were characterized using UV–vis spectrophotometry, Fourier transfer infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The Ag NPs-PGG films were evaluated for their physical and mechanical properties and cytotoxicity and were found to have high tensile strength, flexibility and biocompatibility. The films were also subjected to an in-door soil burial test for 15 days and were observed to decompose rapidly. The developed Ag NPs-PGG composite films with bactericidal properties have potential use in food packaging and various biomedical applications.

Synthesis, Characterization and Biomedical Application of Silver Nanoparticles

Silver nanoparticles (AgNPs) have been employed in various fields of biotechnology due to their proven properties as an antibacterial, antiviral and antifungal agent. AgNPs are generally synthesized through chemical, physical and biological approaches involving a myriad of methods. As each approach confers unique advantages and challenges, a trends analysis of literature for the AgNPs synthesis using different types of synthesis were also reviewed through a bibliometric approach. A sum of 10,278 publications were analyzed on the annual numbers of publication relating to AgNPs and biological, chemical or physical synthesis from 2010 to 2020 using Microsoft Excel applied to the Scopus publication database. Furthermore, another bibliometric clustering and mapping software were used to study the occurrences of author keywords on the biomedical applications of biosynthesized AgNPs and a total collection of 224 documents were found, sourced from articles, reviews, book chapters, conference papers and reviews. AgNPs provides an excellent, dependable, and effective solution for seven major concerns: as antibacterial, antiviral, anticancer, bone healing, bone cement, dental applications and wound healing. In recent years, AgNPs have been employed in biomedical sector due to their antibacterial, antiviral and anticancer properties. This review discussed on the types of synthesis, how AgNPs are characterized and their applications in biomedical field.

Acidic Dressing Based on Agarose/Cs2.5H0.5PW12O40 Nanocomposite for Infection Control in Wound Care

Regulation of wound pH from alkaline to acidic is a simple and powerful approach to reduce wound microbial colonization and infection. Here, we present a nanocomposite material possessing intrinsic acidic surface pH as an innovative antimicrobial wound dressing. This material comprises an agarose matrix nanocomposite containing nanoparticles (NPs) of the cesium salt of phosphotungstic heteropolyacid (Cs_2.5H_0.5PW₁₂O₄₀). Self-supporting films were prepared by a casting method incorporating 5-20 wt % Cs_2.5H_0.5PW₁₂O₄₀ NPs into the matrix. Films are flexible with tensile strengths between 28.55 and 32.15 MPa and exhibit broad biocidal activity against neutralophilic pathogens, including Gram-positive bacteria, Gram-negative bacteria, yeast, and filamentous fungi. The nano-antimicrobial Cs_2.5H_0.5PW₁₂O₄₀ functions as an efficient and self-controlled proton delivery agent that lowers the surface pH of the nanocomposites to the range 7.0 > pH ≥ 3.0. Nanocomposite films containing 20 wt % Cs_2.5H_0.5PW₁₂O₄₀ NPs presented a surface pH of 3.0 and highest antimicrobial activity. Using quantitative reverse transcription polymerase chain reaction, we demonstrated that the antimicrobial mechanism of the nanocomposites is acid-induced because of the transcriptional induction of glutamate-dependent acid resistance genes in Escherichia coli. Additionally, nanocomposite films do not damage skin according to an in vivo rabbit skin model with no derived edema or erythema. The wound care safety of this material is due to low release of heavy metal heteropolyanions ([PW₁₂O₄₀]^3-), no nanoparticle leaching, and proton controlled release resulting in nonirritating acid levels for human skin models.

Preparation and Characterization of Silver Sulfadiazine-Loaded Polyvinyl Alcohol Hydrogels as an Antibacterial Wound Dressing

In this study, we prepared a series of silver sulfadiazine (AgSD)-loaded polyvinyl alcohol (PVA) hydrogels via electron beam (e-beam) irradiation. Our objective was to explore the influence of e-beam irradiation on the chemical structure and crystallinity of AgSD and the antibacterial properties of AgSD/PVA hydrogels. Prior to irradiation, we mixed AgSD in PVA solution in 2 forms, either suspended in water (WS) or dissolved in ammonia solution (AS). We noted that nano silver was released from AgSD/PVA-AS hydrogels immersed in deionized water, while it would not happen in AgSD/PVA-WS hydrogels. Both kinds of AgSD/PVA hydrogels exhibited good antibacterial activities against gram-negative Escherichia coli and gram-positive Staphylococcus aureus. And their antibacterial activity was not obviously affected by different dosages of e-beam irradiation. Moreover, the antibacterial activity of the AgSD/PVA-WS hydrogels was stronger than that of AgSD/PVA-AS. Accordingly, the cell cytotoxicity of the AgSD/PVA-WS hydrogels was higher than that of AgSD/PVA-AS. Our study results reveal that e-beam irradiation of PVA solution with dispersed AgSD is a simple and efficient way to prepare AgSD/PVA hydrogels, which might be an ideal antibacterial wound dressing.

3D-Hydrogel Based Polymeric Nanoreactors for Silver Nano-Antimicrobial Composites Generation

This study underscores the development of Ag hydrogel nanocomposites, as smart substrates for antibacterial uses, via innovative in situ reactive and reduction pathways. To this end, two different synthetic strategies were used. Firstly thiol-acrylate (PSA) based hydrogels were attained via thiol-ene and radical polymerization of polyethylene glycol (PEG) and polycaprolactone (PCL). As a second approach, polyurethane (PU) based hydrogels were achieved by condensation polymerization from diisocyanates and PCL and PEG diols. In fact, these syntheses rendered active three-dimensional (3D) hydrogel matrices which were used as nanoreactors for in situ reduction of AgNO₃ to silver nanoparticles. A redox chemistry of stannous catalyst in PU hydrogel yielded spherical AgNPs formation, even at 4 °C in the absence of external reductant; and an appropriate thiol-functionalized polymeric network promoted spherical AgNPs well dispersed through PSA hydrogel network, after heating up the swollen hydrogel at 103 °C in the presence of citrate-reductant. Optical and swelling behaviors of both series of hydrogel nanocomposites were investigated as key factors involved in their antimicrobial efficacy over time. Lastly, in vitro antibacterial activity of Ag loaded hydrogels exposed to Pseudomona aeruginosa and Escherichia coli strains indicated a noticeable sustained inhibitory effect, especially for Ag-PU hydrogel nanocomposites with bacterial inhibition growth capabilities up to 120 h cultivation.

Microfluidic assisted synthesis of silver nanoparticle-chitosan composite microparticles for antibacterial applications

Silver nanoparticle (Ag NP)-loaded chitosan composites have numerous biomedical applications; however, fabricating uniform composite microparticles remains challenging. This paper presents a novel microfluidic approach for single-step and in situ synthesis of Ag NP-loaded chitosan microparticles. This proposed approach enables obtaining uniform and monodisperse Ag NP-loaded chitosan microparticles measuring several hundred micrometers. In addition, the diameter of the composites can be tuned by adjusting the flow on the microfluidic chip. The composite particles containing Ag NPs were characterized using UV-vis spectra and scanning electron microscopy-energy dispersive X-ray spectrometry data. The characteristic peaks of Ag NPs in the UV-vis spectra and the element mapping or pattern revealed the formation of nanosized silver particles. The results of antibacterial tests indicated that both chitosan and composite particles showed antibacterial ability, and Ag NPs could enhance the inhibition rate and exhibited dose-dependent antibacterial ability. Because of the properties of Ag NPs and chitosan, the synthesized composite microparticles can be used in several future potential applications, such as bactericidal agents for water disinfection, antipathogens, and surface plasma resonance enhancers.

In situ assembly of antifouling/bacterial silver nanoparticle-hydrogel composites with controlled particle release and matrix softening

Controlling bacterial contamination has been a major challenge for protecting human health and welfare. In this context, hydrogels loaded with silver nanoparticles have been used to prevent biofilm formation on substrates of interest. However, such gel composites are often plagued by rapid loss of silver nanoparticles and matrix softening, and thus the gel becomes less effective for antifouling. To this end, this study demonstrates that in situ photoreaction of an aqueous mixture of silver nitrates, poly(ethylene glycol) diacrylate, and vinylpyrrolidone results in a silver nanoparticle-laden hydrogel composite with minimal nanoparticle loss and matrix softening due to enhanced binding between nanoparticles and the gel. The resulting gel composite successfully inhibits the bacterial growth in media and the bacterial adhesion to surfaces of interest. We suggest that the results of this study serve to advance quality of materials with antifouling/bacterial activities.