A novel poly(γ-glutamic acid)/silk-sericin hydrogel for wound dressing: Synthesis, characterization and biological evaluation

Repairing effect of magnesium oxychloride cement modified by γ-polyglutamic acid and chitosan in osteoporotic bone defect

Magnesium oxychloride cement (MOC) has the advantage of high early strength. However, it has the defect of poor water resistance. Considering this performance, we use γ-polyglutamic acid (γ-PGA) and chitosan (CS) to modify MOC. The effects of γ-PGA and CS such as strength, in vitro degradation and in vitro bioactivity of MOC were studied. Based on the preparation of γ-PGA and CS modified MOC (γ-PGA/CS-MOC) composite bone cement, the strontium ranelate (SrR) was loaded on. The results showed that the softening coefficient of γ-PGA/3 wt.% CS-MOC after soaking in SBF for 28 d reached 0.48, while that of control group (without CS and γ-PGA) was only 0.35; Cell experiments indicated that SrR could promote differentiation into osteoblasts. After the γ-PGA/CS-MOC composite bone cement containing SrR was implanted into the osteoporotic bone defect for 12 w, it was found that the material was gradually absorbed and the new bone tissue grew. The results showed that SrR/γ-PGA/CS-MOC composite bone cement had a potential application prospect in the repair of osteoporotic bone defects.

Expanding the boundaries of silk sericin biomaterials in biomedical applications

Silk sericin (SS) has a long history as a by-product of the textile industry. SS has emerged as a sustainable material for biomedical engineering due to its material properties including water solubility, diverse impact on biological activities including antibacterial and antioxidant properties, and ability to promote cell adhesion and proliferation. This review addresses the origin, structure, properties, extraction, and underlying functions of this protein. An overview of the growing research studies and market evolution is presented, along with highlights of the most common fabrication matrices (hydrogels, bioinks, porous and fibrous scaffolds) and tissue engineering applications. Finally, the future trends with this protein as a multifaceted toolbox for bioengineering are explored, along with the challenges with SS. Overall, the present review can serve as a foundation for the creation of innovative biomaterials utilizing SS as a fundamental building block that hold market potential.

Hydrogel-Based Skin Regeneration

The skin is subject to damage from the surrounding environment. The repair of skin wounds can be very challenging due to several factors such as severe injuries, concomitant infections, or comorbidities such as diabetes. Different drugs and wound dressings have been used to treat skin wounds. Tissue engineering, a novel therapeutic approach, revolutionized the treatment and regeneration of challenging tissue damage. This field includes the use of synthetic and natural biomaterials that support the growth of tissues or organs outside the body. Accordingly, the demand for polymer-based therapeutic strategies for skin tissue defects is significantly increasing. Among the various 3D scaffolds used in tissue engineering, hydrogel scaffolds have gained special significance due to their unique properties such as natural mimicry of the extracellular matrix (ECM), moisture retention, porosity, biocompatibility, biodegradability, and biocompatibility properties. First, this article delineates the process of wound healing and conventional methods of treating wounds. It then presents an examination of the structure and manufacturing methods of hydrogels, followed by an analysis of their crucial characteristics in healing skin wounds and the most recent advancements in using hydrogel dressings for this purpose. Finally, it discusses the potential future advancements in hydrogel materials within the realm of wound healing.

An Insight into Biodegradable Polymers and their Biomedical Applications for Wound Healing

Biodegradable polymers, encompassing both natural and synthetic polymers, have demonstrated efficacy as carriers for synthetic drugs, natural bioactive molecules, and inorganic metals. This is due to their ability to control the release of these substances. As a result, various advanced materials, such as nanoparticle- loaded hydrogels, nanofibrous scaffolds, and nanocomposites, have been developed. These materials have shown promise in enhancing processes, such as cell proliferation, vascular angiogenesis, hair growth, and wound healing management. Natural polymers, including hyaluronic acid, collagen, chitosan, gelatin, and alginate, as well as synthetic polymers like polylactic acid, polyglycolic acid, polylactic co-glycolic acid, and PCA, have significant potential for promoting wound healing. This study examines the advancements in biodegradable polymers for wound healing, specifically focusing on each polymer and its distinctive formulations. It also discusses the in vitro experiments conducted using different cell lines, as well as the in vivo studies that explore the numerous uses of these polymers in wound healing. The discussion also included the exploration of modifications or combinations of several polymers, as well as surface changes, in order to produce synergistic effects and address the limitations of individual polymers. The goal was to expedite the healing process of different chronic wounds. Due to this, there have been notable advancements in the technological use of polymeric mixes, including biodegradable polymer-based scaffolds, which have accelerated the process of wound healing.

Synthesis of Poly-γ-Glutamic Acid and Its Application in Biomedical Materials

Poly-γ-glutamic acid (γ-PGA) is a natural polymer composed of glutamic acid monomer and it has garnered substantial attention in both the fields of material science and biomedicine. Its remarkable cell compatibility, degradability, and other advantageous characteristics have made it a vital component in the medical field. In this comprehensive review, we delve into the production methods, primary application forms, and medical applications of γ-PGA, drawing from numerous prior studies. Among the four production methods for PGA, microbial fermentation currently stands as the most widely employed. This method has seen various optimization strategies, which we summarize here. From drug delivery systems to tissue engineering and wound healing, γ-PGA's versatility and unique properties have facilitated its successful integration into diverse medical applications, underlining its potential to enhance healthcare outcomes. The objective of this review is to establish a foundational knowledge base for further research in this field.

UV-polymerizable methacrylated gelatin (GelMA)-based hydrogel containing tannic acids for wound healing

Gelatin-based photopolymerizable methacrylate hydrogel (GelMA) is a promising biomaterial for in situ drug delivery, while aqueous extract of Punica granatum (AEPG) peel fruit rich in gallic acid and ellagic acid is used to improve wound healing. The aim of this study was to develop and analyze the healing properties of GelMA containing AEPG, gallic acid, or ellagic acid in a rodent model. GelMA hydrogels containing 5% AEPG (GelMA-PG), 1.6% gallic acid (GelMA-GA), or 2.1% ellagic acid (GelMA-EA) were produced and their mechanical properties, enzymatic degradation, and thermogravimetric profile determined. Wound closure rates, healing histological grading, and immunohistochemical counts of myofibroblasts were assessed over time. The swelling of hydrogels varied between 50 and 90%, and GelMA exhibited a higher swelling than the other groups. The GPG samples showed higher compression and Young's moduli than GelMA, GGA, and GAE. All samples degraded around 95% in 48 h. GPG and GGA significantly accelerated wound closure, improved collagenization, increased histological grading, and hastened myofibroblast differentiation in comparison to the control, GelMA, and GEA. GelMA containing AEPG (GPG) improved wound healing, and although gallic acid is the major responsible for such biological activity, a potential synergic effect played by other polyphenols present in the extract is evident.

Porous Poly(2-hydroxyethyl methacrylate) Hydrogel Scaffolds for Tissue Engineering: Influence of Crosslinking Systems and Silk Sericin Concentration on Scaffold Properties

Tailored porous structures of poly(2-hydroxyethyl methacrylate) (PHEMA) and silk sericin (SS) were used to create porous hydrogel scaffolds using two distinct crosslinking systems. These structures were designed to closely mimic the porous nature of the native extracellular matrix. Conventional free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) was performed in the presence of different concentrations of SS (1.25, 2.50, 5.00% w/v) with two crosslinking systems. A chemical crosslinking system with N'N-methylene bisacrylamide (MBAAm) and a physical crosslinking system with dimethylurea (DMU) were used: C-PHEMA/SS (crosslinked using MBAAm) and C-PHEMA/pC-SS (crosslinked using MBAAm and DMU). The focus of this study was on investigating the impact of these crosslinking methods on various properties of the scaffolds, including pore size, pore characteristics, polymerization time, morphology, molecular interaction, in vitro degradation, thermal properties, and in vitro cytotoxicity. The various crosslinked networks were found to appreciably influence the properties of the scaffolds, especially the pore sizes, in which smaller sizes and higher numbers of pores with high regularity were seen in C-PHEMA/1.25 pC-SS (17 ± 2 μm) than in C-PHEMA/1.25 SS (34 ± 3 μm). Semi-interpenetrating networks were created by crosslinking PHEMA-MBAAm-PHEMA while incorporating free protein molecules of SS within the networks. The additional crosslinking step involving DMU occurred through hydrogen bonding of the -C=O and -N-H groups with the SS, resulting in the simultaneous incorporation of DMU and SS within the PHEMA networks. As a consequence of this process, the scaffold C-PHEMA/pC-SS exhibited smaller pore sizes compared to scaffolds without DMU crosslinking. Moreover, the incorporation of higher loadings of SS led to even smaller pore sizes. Additionally, the gelation time of C-PHEMA/pC-SS was delayed due to the presence of DMU in the crosslinking system. Both porous hydrogel scaffolds, C-PHEMA/pC-SS and PHEMA, were found to be non-cytotoxic to the normal human skin dermal fibroblast cell line (NHDF cells). This promising result indicates that these hydrogel scaffolds have potential for use in tissue engineering applications.

A comprehensive review of recent advances in silk sericin: Extraction approaches, structure, biochemical characterization, and biomedical applications

Silks are natural polymers that have been widely used for centuries. Silk consists of a filament core protein, termed fibroin, and a glue-like coating substance formed of sericin (SER) proteins. This protein is extracted from the silkworm cocoons (particularly Bombyx mori) and is mainly composed of amino acids like glycine, serine, aspartic acid, and threonine. Silk SER can be obtained using numerous methods, including enzymatic extraction, high-temperature, autoclaving, ethanol precipitation, cross-linking, and utilizing acidic, alkali, or neutral aqueous solutions. Given the versatility and outstanding properties of SER, it is widely fabricated to produce sponges, films, and hydrogels for further use in diverse biomedical applications. Hence, many authors reported that SER benefits cell proliferation, tissue engineering, and skin tissue restoration thanks to its moisturizing features, antioxidant and anti-inflammatory properties, and mitogenic effect on mammalian cells. Remarkably, SER is used in drug delivery depending on its chemical reactivity and pH-responsiveness. These unique features of SER enhance the bioactivity of drugs, facilitating the fabrication of biomedical materials at nano- and microscales, hydrogels, and conjugated molecules. This review thoroughly outlines the extraction techniques, biological properties, and respective biomedical applications of SER.

The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

A hydrogel dressing with tunable critical temperature and photothermal modulating melittin release for multiply antibacterial treatment

It is imperative to develop an antibiotic-free and long-term effective strategy for treating chronic wound infections due to the long-term utilization of antibiotics easily causing drug resistance. Herein, we fabricated a novel poly-N-isopropylacrylamide (PNIPAM)/polyacrylamide (PAM) coupling thermosensitive hydrogel integrating 1D lysozyme nanofiber doped with CuS nanoparticles (CuS/PP) and loading antibacterial peptide melittin (M) (CuS/PP-M) for combating chronic wound infection via photothermal modulating the release of melittin. For the CuS/PP-M hydrogel, the copolymerization of PNIPAM and PAM allows the lower critical solution temperature (LCST) higher than the body temperature, effectively hindering the spontaneous release of melittin when contacts the infected wound, while the integration of LNF/CuS nanofibers provides a stable photothermal treatment for triggering the release of melittin. As a result, the CuS/PP-M hydrogel exhibits synergistically enhanced effect on killing both Gram-positive and Gram-negative bacteria, which maintains more than 99 % bactericidal efficiency, even displays a long-term and multiply antibacterial performance by photothermal modulating melittin release. Moreover, the CuS/PP-M hydrogel presents both high antibacterial activity and excellent wound healing performance in the mouse wound model, thereby benefiting the chronic wound healing.

Silk sericin-based materials for biomedical applications

Silk sericin, a natural protein extracted from silkworm cocoons, has been extensively studied and utilized in the biomedical field because of its superior biological activities and controllable chemical-physical properties. Sericin is biocompatible and naturally cell adhesive, enabling cell attachment, proliferation, and differentiation in sericin-based materials. Moreover, its abundant functional groups from variable amino acids composition allow sericin to be chemically modified and cross-linked to form versatile constructs serving as alternative matrixes for biomedical applications. Recently, sericin has been constructed into various types of biomaterials for tissue engineering and regenerative medicine, including various bulk constructions (films, hydrogels, scaffolds, conduits, and devices) and micro-nano formulations. In this review, we systemically summarize the properties of silk sericin, introduce its different forms, and demonstrate their newly-developed as well as potential biomedical applications.

Progress in hydrogels for skin wound repair

As the first defensive line between the human body and the outside world, the skin is vulnerable to damage from the external environment. Skin wounds can be divided into acute wounds (mechanical injuries, chemical injuries and surgical wounds, etc.) and chronic wounds (burns, infections, diabetes, etc.). In order to manage skin wound, a variety of wound dressings have been developed, including gauze, films, foams, nanofibers, hydrocolloids and hydrogels. Recently, hydrogels have received much attention because of their natural extracellular matrix (ECM)-mimik structure, tunable mechanical properties, and facile bioactive substance delivery capability. They show great potential application in skin wound repair. This paper first introduces the anatomy and function of the skin, the process of wound healing and conventional wound dressings, and then introduces the composition and construction methods of hydrogels. Next, this paper introduces the necessary properties of hydrogels in skin wound repair and the latest research progress of hydrogel dressings for skin wound repair. Finally, the future development goals of hydrogel materials in the field of wound healing are proposed. This article is protected by copyright. All rights reserved.

Chitosan/Polyvinyl Alcohol/ Lauramidopropyl Betaine/2D-HOF Mixed Film with Abundant Hydrogen Bonds Acts as High Mechanical Strength Artificial Skin

The mechanical properties of artificial skins are complicated to maintain under ensuring air permeability and antimicrobial. Thus, a series of hydrophilic antimicrobial polymer networks are prepared by crosslinking chitosan and polyvinyl alcohol with the lauramidopropyl betaine and hydrogen bond organic framework (CS/PVA/LPB/2D-HOF). The mechanical performance of the control groups and the complex are systematically evaluated to attain an artificial strength skin. The CS/PVA/LPB/2D-HOF complex exhibits strong mechanical abilities than other control groups. By analyzing the IR spectra and the morphology, the synergistic effect of hydrogen bonds between molecules and cracks significantly improves the mechanical properties of the complex. Its maximum tensile strength can reach 29 MPa, and its maximum load capacity can reach 3700 g. Notably, the composite membrane also performs an excellent antimicrobial activity. In vivo and in vitro experiments show that the hybrid membrane can promote tissue regeneration and wound healing (95％). These results may open up the opportunity for future composite material investigations in the artificial skin and tissue engineering field.

An Integrated Smart Sensor Dressing for Real-Time Wound Microenvironment Monitoring and Promoting Angiogenesis and Wound Healing

Prolonged chronic wound healing not only places great stress on patients but also increase the health care burden. Fortunately, the emergence of tissue-engineered dressings has provided a potential solution for these patients. Recently, the relationship between the wound microenvironment and wound healing has been gradually clarified. Therefore, the state of wounds can be roughly ascertained by monitoring the microenvironment in real time. Here, we designed a three-layer integrated smart dressing, including a biomimetic nanofibre membrane, microenvironment sensor and β-cyclodextrin-containing gelatine methacryloyl (GelMA + β-cd) UV-crosslinked hydrogel. The hydrogel helped increase the expression of vascular endothelial growth factor (VEGF) through hypoxia-inducible factor-1α (HIF-1α) to promote neovascularization and wound healing. The microenvironment sensor, combined with the biological dressings, exhibited satisfactory measurement accuracy, stability, durability and biocompatibility. A BLE4.0 antenna was used to receive, display and upload wound microenvironment data in real time. Such integrated smart dressings can not only achieve biological functions but also monitor changes in the wound microenvironment in real time. These dressings can overcome the challenge of not knowing the state of the wound during the healing process and provide support for clinical work.

In Situ Forming Silk Sericin-Based Hydrogel: A Novel Wound Healing Biomaterial

In situ cross-linked hydrogels have the advantage of effectively fulfilling the wound in its shape and depth. Amongst the new generation of natural-based biopolymers being proposed for wound care and skin regeneration, silk sericin is particularly interesting due to its exceptional properties such as biocompatibility, biodegradability, and antioxidant behavior, among others. In this study, a new enzyme-mediated cross-linked hydrogel composed of silk sericin is proposed for the first time. The developed hydrogel cross-linking strategy was performed via horseradish peroxidase, under physiological conditions, and presented gelling kinetics under 3 min, as demonstrated by its rheological behavior. The hydrogels presented a high degree of transparency, mainly due to their amorphous conformation. Degradation studies revealed that the hydrogels were stable in phosphate buffer solution (PBS) (pH 7.4) for 17 days, while in the presence of protease XIV (3.5 U/mg) and under acute and chronic physiological pH values, the stability decreased to 7 and 4 days, respectively. During protease degradation, the present sericin hydrogels demonstrated antioxidant activity. In vitro studies using an L929 fibroblast cell line demonstrated that these hydrogels were noncytotoxic, promoting cell adhesion and massive cell colonization after 7 days of culture, demonstrating that cells maintained their viability and proliferation. In addition, the application of sericin-based hydrogel in an in vivo diabetic wound model validated the feasibility of the in situ methodology and demonstrated a local anti-inflammatory effect, promoting the healing process. This study presents a simple, fast, and practical in situ approach to produce a sericin-based hydrogel able to be applied in low exudative chronic wounds. Moreover, the study herein reported fosters the valorization of a textile industrial by-product by its integration in the biomedical field.

Hidrogeles de colágeno acoplados con hidroxiapatita para aplicaciones en ingeniería tisular

Los hidrogeles basados en colágeno son redes tridimensionales (3D) con la capacidad de absorber agua y una alta biocompatibilidad para utilizarlos en la reparación de tejidos dañados. Estos materiales presentan pobres propiedades mecánicas y velocidades de degradación rápidas, limitando su aplicación a estrategias de ingeniería tisular y biomedicina; por ésto, la incorporación de fases inorgánicas en la matriz 3D del colágeno como la hidroxiapatita ha contribuido en la mejora de sus propiedades, incrementado la eficiencia de los hidrogeles híbridos obtenidos. Este trabajo, presenta las contribuciones más relevantes relacionadas con los sistemas de hidrogeles basados en colágeno y partículas de hidroxiapatita dispersas dentro de la matriz colagénica, lo que evidencia que la combinación de los materiales no altera la biocompatibilidad y biodegradabilidad típicas del colágeno, permitiendo la adhesión, proliferación, crecimiento celular y control del metabolismo de las células implicadas en los procesos de una reparación ósea, presentando a los hidrogeles como una estrategia para su uso potencial en la ingeniería tisular.

A novel hemostat and antibacterial nanofibrous scaffold based on poly(vinyl alcohol)/poly(lactic acid)

Today, an advanced wound dressing with the ability of blood clotting and antibacterial activity is the main subject of many studies to consider their necessity in modern society. In this study, it was aimed to present a novel scaffold with both abilities simultaneously. Poly(vinyl alcohol)/poly(lactic acid) nanofibrous scaffolds containing ceftriaxone antimicrobial agent (PVA-CTX/PLA) and tranexamic acid coagulant (PVA-CTX-TXA/PLA) were fabricated by electrospinning method. Morphology, antimicrobial activity, blood coagulation and bioavailability indexes, and swelling ability (gel formation) of produced samples were determined. Morphological results showed that the hybrid nanofibers were form successfully. The antibacterial efficiency of them against Gram-negative ( Escherichia coli) and Gram-positive ( Staphylococcus aureus) bacteria was more than 90% for PVA-CTX/PLA and it reached 100% for PVA-CTX-TXA/PLA. Both PVA-CTX-TXA/PLA and PVA-TXA/PLA scaffolds showed acceptable blood coagulation ability with an average absorption of 0.043 and 0.036 nm, respectively. PVA-CTX-TXA/PLA scaffolds had a gel formation ability of about 45 min. All scaffolds were successful in cell proliferation (L929 fibroblast cell) after 48 h.

Poly(N-Isopropyl-Acrylamide)/Poly(γ-Glutamic Acid) Thermo-Sensitive Hydrogels Loaded with Superoxide Dismutase for Wound Dressing Application

INTRODUCTION

Chronic trauma repair is an important issue affecting people's healthy lives. Thermo-sensitive hydrogel is injectable in situ and can be used to treat large-area wounds. In addition, antioxidants play important roles in promoting wound repair.

METHODS

The purpose of this research was to prepare a novel thermo-sensitive hydrogel-poly(N-isopropyl-acrylamide)/poly(γ-glutamic acid) (PP) loaded with superoxide dismutase (SOD) to improve the effect for trauma treatment. The micromorphology of the hydrogel was observed by scanning electron microscope and the physical properties were measured. The biocompatibility of hydrogel was evaluated by MTT experiment, and the effect of hydrogel on skin wound healing was evaluated by in vivo histological staining.

RESULTS

Gelling behavior and differential scanning calorimeter outcomes showed that the PP hydrogels possessed thermo-sensitivity at physiological temperature and the phase transformation temperature was 28.2°C. The high swelling rate and good water retention were conducive to wound healing. The activity of SOD in vitro was up to 85% at 10 h, which was advantageous to eliminate the superoxide anion. MTT assay revealed that this hydrogel possessed good biocompatibility. Dressings of PP loaded with SOD (SOD-PP) had a higher wound closure rate than other treatments in vivo in diabetic rat model.

DISCUSSION

The SOD-PP thermo-sensitive hydrogels can effectively promote wound healing and have good application prospects for wound repair.

Development of the PVA/CS nanofibers containing silk protein sericin as a wound dressing: In vitro and in vivo assessment

Skin and soft tissue infections are major concerns with respect to wound repair. Recently, anti-bacterial wound dressings have been emerging as promising candidates to reduce infection, thus accelerating the wound healing process. This paper presents our work to develop and characterize poly(vinyl alcohol) (PVA)/chitosan (CS)/silk sericin (SS)/tetracycline (TCN) porous nanofibers, with diameters varying from 305 to 425 nm, both in vitro and in vivo for potential applications as wound dressings. The fabricated nanofibers possess a considerable capacity to take up water through swelling (~325-650%). Sericin addition leads to increased hydrophilicity and elongation at break while decreasing fiber diameter and mechanical strength. Moreover, fibroblasts (L929) cultured on the nanofibers with low sericin content (PVA/CS/1-2SS) displayed greater proliferation compared to those on nanofibers without sericin (PVA/CS). Nanofibers loaded with high sericin and tetracycline content significantly inhibited the growth of Escherichia coli and Staphylococcus aureus. In vivo examination revealed that PVA/CS/2SS-TCN nanofibers enhance wound healing, re-epithelialization, and collagen deposition compared to traditional gauze and nanofibers without sericin. The results of this study demonstrate that the PVA/CS/2SS-TCN nanofiber creates a promising alternative to traditional wound dressing materials.

Silk sericin-enhanced microstructured bacterial cellulose as tissue engineering scaffold towards prospective gut repair

As a first step towards the production of functional cell sheets applicable for the regeneration of gut muscle layer, microstructured bacterial cellulose (mBC) was assessed for its ability to support the growth of enteric nervous system (ENS) and gut smooth muscle cells (SMCs). To improve the cellular response, mBC was modified with silk sericin (SS) which has renowned abilities in supporting tissue regeneration. While SS did not impair the line structures imparted to BC by PDMS templates, similarly to the patterns, it affected its physical properties, ultimately leading to variations in the behavior of cells cultured onto these substrates. Enabled by the stripes on mBC, both SMCs and ENS cells were aligned in vitro, presenting the in vivo-like morphology essential for peristalsis and gut function. Interestingly, cell growth and differentiation remarkably enhanced upon SS addition to the samples, indicating the promise of the mBC-SS constructs as biomaterial not only for gut engineering, but also for tissues where cellular alignment is required for function, namely the heart, blood vessels, and similars.

Cornstarch-based wound dressing incorporated with hyaluronic acid and propolis: In vitro and in vivo studies

The unique physicochemical and functional characteristics of starch-based biomaterials and wound dressings have been proposed for several biomedical applications. Film dressings of cornstarch/hyaluronic acid/ ethanolic extract of propolis (CS/HA/EEP) were prepared by solvent-casting and characterized by attenuated total reflectance/Fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography/mass spectrometry, light transmission, opacity measurements, EEP release, equilibrium swelling, and in vitro and in vivo evaluations. The CS/HA/0.5%EEP film dressing exhibited higher antibacterial activity against Staphylococcus aureus (2.08 ± 0.14 mm), Escherichia coli (2.64 ± 0.18 mm), and Staphylococcus epidermidis (1.02 ± 0.15 mm) in comparison with the CS, CS/HA, and CS/HA/0.25%EEP films. Also, it showed no cytotoxicity for the L929 fibroblast cells. This wound dressing could effectively accelerate the wound healing process at Wistar rats' skin excisions. These results indicate that enrichment of cornstarch wound dressings with HA and EEP can significantly enhance their potential efficacy as wound dressing material.

Electrospun Poly(γ⁻glutamic acid)/β⁻Tricalcium Phosphate Composite Fibrous Mats for Bone Regeneration

A poly(γ–glutamic acid)/β–tricalcium phosphate (γ–PGA/β–TCP) composite fibrous mat was fabricated using the electrospinning technique as a novel bone substitute. The mat was then cross-linked with cystamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide to improve its water-resistant ability. Scanning electron micrographs revealed that the γ–PGA/β–TCP fibers had a uniform morphology with diameters ranging from 0.64 ± 0.07 µm to 1.65 ± 0.16 µm. The average diameter of the fibers increased with increasing cross-linking time. Moreover, increasing the cross-linking time and decreasing the γ–PGA/β–TCP weight ratio decreased the swelling ratio and in vitro degradation rate of the composite fibrous mat. In vitro experiments with osteoblast-like MG-63 cells demonstrated that the mat with a γ–PGA/β–TCP weight ratio of 20 and cross-linked time of 24 h had a higher alkaline phosphatase activity and better cell adhesion. Furthermore, the rat cranial bone defect was created and treated with the γ–PGA/β–TCP composite fibrous mat to evaluate its potential in bone regeneration. After 8 weeks of implantation, micro computed tomography showed that the γ–PGA/β–TCP composite fibrous mat promoted new bone growth. These observations suggest that the γ–PGA/β–TCP composite fibrous mat has a potential application in bone tissue engineering.

Pectin-honey hydrogel: Characterization, antimicrobial activity and biocompatibility

BACKGROUND

Novel pectin-honey hydrogels have been developed and characterized as medical device. Ideally, a wound dressing should maintain optimal fluid affinity, permit moisture evaporation, protect the wound from microbes, and have shape-conformability, biocompatibility, and antibacterial activity.

OBJECTIVE

A novel, simple and fast method to produce pectin-honey wound dressings is described.

METHODS

The properties of these pectin-honey hydrogels were investigated, including swelling ability, water vapour transmission rate, hydrogen peroxide production, methylglyoxal content and antibacterial activity. Biocompatibility was assessed by proliferation assays using cultured fibroblast cells and by in vivo study with subcutaneous and intraperitoneal implantation in rats.

RESULTS

Hydrogel showed a good water vapour transmission rate, fluid uptake and were not cytotoxic for fibroblasts. The hydrogel demonstrated good antibacterial activity toward clinically relevant pathogens, including S. aureus and E. coli. Biocompatibility was confirmed by the measurement of plasma levels of interleukin (IL)1 beta, IL-6, tumour necrosis factor (TNF) alpha, and prostaglandin (PG)E2. No histological changes were observed.

CONCLUSIONS

The presence of a natural active component, conformability, and complete resorbability are the main characteristics of this new biocompatible biomaterial that is well tolerated by the body, possibly improves healing, may be used for surgical complications prevention, with a simple and inexpensive production process.

Biomedical Potential of Ultrafine Ag Nanoparticles Coated on Poly (Gamma-Glutamic Acid) Hydrogel with Special Reference to Wound Healing

In wound care management, the prevention of wound infection and the retention of an appropriate level of moisture are two major challenges. Therefore, designing an excellent antibacterial hydrogel with a suitable water-adsorbing capacity is very important to improve the development of wound dressings. In this paper, a novel silver nanoparticles/poly (gamma-glutamic acid) (γ-PGA) composite dressing was prepared for biomedical applications. The promoted wound-healing ability of the hydrogels were systematically evaluated with the aim of attaining a novel and effective wound dressing. A diffusion study showed that hydrogels can continuously release antibacterial factors (Ag). Hydrogels contain a high percentage of water, providing an ideal moist environment for tissue regeneration, while also preventing contraction of the wound. Moreover, an in vivo, wound-healing model evaluation of artificial wounds in mice indicated that silver/γ-PGA hydrogels could significantly promote wound healing. Histological examination revealed that hydrogels can successfully help to reconstruct intact epidermis and collagen deposition during 14 days of impaired wound healing. Overall, this research could shed new light on the design of antibacterial silver/γ-PGA hydrogels with potential applications in wound dressing.

Accelerated Healing of Diabetic Wounds Treated with L-Glutamic acid Loaded Hydrogels Through Enhanced Collagen Deposition and Angiogenesis: An In Vivo Study

We have developed L-glutamic acid (LG) loaded chitosan (CS) hydrogels to treat diabetic wounds. Although literature reports wound healing effects of poly(glutamic acid)-based materials, there are no studies on the potential of L-glutamic acid in treating diabetic wounds. As LG is a direct precursor for proline synthesis, which is crucial for collagen synthesis, we have prepared CS + LG hydrogels to accelerate diabetic wound healing. Physiochemical properties of the CS + LG hydrogels showed good swelling, thermal stability, smooth surface morphology, and controlled biodegradation. The addition of LG to CS hydrogels did not alter their biocompatibility significantly. CS + LG hydrogel treatment showed rapid wound contraction compared to control and chitosan hydrogel. Period of epithelialization is significantly reduced in CS + LG hydrogel treated wounds (16 days) compared to CS hydrogel (20 days), and control (26 days). Collagen synthesis and crosslinking are also significantly improved in CS + LG hydrogel treated diabetic rats. Histopathology and immunohistochemistry results revealed that the CS + LG hydrogel dressing accelerated vascularization and macrophage recruitment to enhance diabetic wound healing. These results demonstrate that incorporation of LG can improve collagen deposition, and vascularization, and aid in faster tissue regeneration. Therefore, CS + LG hydrogels could be an effective wound dressing used to treat diabetic wounds.

Effects of Silk Sericin on Incision Wound Healing in a Dorsal Skin Flap Wound Healing Rat Model

Background

The wound healing process is complex and still poorly understood. Sericin is a silk protein synthesized by silk worms (Bombyx mori). The objective of this study was to evaluate in vivo wound healing effects of a sericin-containing gel formulation in an incision wound model in rats.

Material/Methods

Twenty-eight Wistar-Albino rats were divided into 4 groups (n=7). No intervention or treatment was applied to the Intact control group. For other groups, a dorsal skin flap (9×3 cm) was drawn and pulled up with sharp dissection. The Sham operated group received no treatment. The Placebo group received placebo gel without sericin applied to the incision area once a day from day 0 to day 9. The Sericin Group 3 received 1% sericin gel applied to the incision area once a day from day 0 to day 9. Hematoxylin and eosin stain was applied for histological analysis and Mallory-Azan staining was applied for histoimmunochemical analysis of antibodies and iNOS (inducible nitric oxide synthase), and desmin was applied to paraffin sections of skin wound specimens. Parameters of oxidative stress were measured in the wound area.

Results

Epidermal thickness and vascularization were increased, and hair root degeneration, edema, cellular infiltration, collagen discoloration, and necrosis were decreased in Sericin group in comparison to the Placebo group and the Sham operated group. Malonyldialdehyde (MDA) levels were decreased, but superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were increased in the sericin group.

Conclusions

We found that sericin had significant positive effects on wound healing and antioxidant activity. Sericin-based formulations can improve healing of incision wounds.

Quickly promoting angiogenesis by using a DFO-loaded photo-crosslinked gelatin hydrogel for diabetic skin regeneration

A desferrioxamine (DFO)-loaded photo-crosslinked gelatin hydrogel was used to reconstruct vessel network and prompt skin regeneration in diabetic wounds.

Structure and properties of semi-interpenetrating network hydrogel based on starch

Starch-g-P(acrylic acid-co-acrylamide)/PVA semi-interpenetrating network (semi-IPN) hydrogels were prepared by aqueous solution polymerization method. Starch grafting copolymerization reaction, semi-IPN structure and crystal morphology were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The PVA in the form of partial crystallization distributing in the gel matrix uniformly were observed by Field emission scanning electron microscope (FESEM). The space network structure, finer microstructure and pore size in the interior of hydrogel were presented by biomicroscope. The results demonstrated that absorption ratio of water and salt generated different degree changes with the effect of PVA. In addition, the mechanical strength of hydrogel was improved.