Hydrogel wound dressings for bioactive treatment of acute and chronic wounds

The Influence of Polysaccharides-Based Material on Macrophage Phenotypes

Macrophage polarization is a key factor in determining the success of implanted tissue engineering scaffolds. Polysaccharides (derived from plants, animals, and microorganisms) are known to modulate macrophage phenotypes by recognizing cell membrane receptors. Numerous studies have developed polysaccharide-based materials into functional biomaterial substrates for tissue regeneration and pharmaceutical application due to their immunostimulatory activities and anti-inflammatory response. They are used as hydrogel substrates, surface coatings, and drug delivery carriers. In addition to their innate immunological functions, the newly endowed physical and chemical properties, including substrate modulus, pore size/porosity, surface binding chemistry, and the mole ratio of polysaccharides in hybrid materials may regulate macrophage phenotypes more precisely. Growing evidence indicates that the sulfation pattern of glycosaminoglycans and proteoglycans expressed on polarized macrophages leads to the changes in protein binding, which may alter macrophage phenotype and influence the immune response. A comprehensive understanding of how different types of polysaccharide-based materials alter macrophage phenotypic changes can be beneficial to predict transplantation/implantation outcomes. This review focuses on recent advances in promoting wound healing and balancing macrophage phenotypes using polysaccharide-based substrates/coatings and new directions to address the limitations in the current understanding of macrophage responses to polysaccharides.

(Macro)molecular self-assembly for hydrogel drug delivery

Hydrogels prepared via self-assembly offer scalable and tunable platforms for drug delivery applications. Molecular-scale self-assembly leverages an interplay of attractive and repulsive forces; drugs and other active molecules can be incorporated into such materials by partitioning in hydrophobic domains, affinity-mediated binding, or covalent integration. Peptides have been widely used as building blocks for self-assembly due to facile synthesis, ease of modification with bioactive molecules, and precise molecular-scale control over material properties through tunable interactions. Additional opportunities are manifest in stimuli-responsive self-assembly for more precise drug action. Hydrogels can likewise be fabricated from macromolecular self-assembly, with both synthetic polymers and biopolymers used to prepare materials with controlled mechanical properties and tunable drug release. These include clinical approaches for solubilization and delivery of hydrophobic drugs. To further enhance mechanical properties of hydrogels prepared through self-assembly, recent work has integrated self-assembly motifs with polymeric networks. For example, double-network hydrogels capture the beneficial properties of both self-assembled and covalent networks. The expanding ability to fabricate complex and precise materials, coupled with an improved understanding of biology, will lead to new classes of hydrogels specifically tailored for drug delivery applications.

Curdlan-Based Hydrogels for Potential Application as Dressings for Promotion of Skin Wound Healing-Preliminary In Vitro Studies

The aim of this work was to establish whether novel curdlan-based hydrogels enriched with Ca²⁺ ions may be considered as potential candidates for dressings, for the acceleration of skin wound healing. Firstly, biomaterials were allocated for evaluation of structural and mechanical properties. Subsequently, the ability of hydrogels to absorb simulated wound fluid and water vapor permeability, as well their capacity to release calcium ions, was evaluated. The biocompatibility of biomaterials was assessed using normal human skin fibroblasts. Importantly, the main features of the obtained curdlan-based hydrogels were compared with those of KALTOSTAT^® (a commercial calcium sodium alginate wound dressing). The obtained results showed that curdlan-based biomaterials possessed a mesoporous structure (pore diameter ranged from 14–48 nm) and exhibited a good ability to absorb simulated wound fluid (swelling ratio close to 974–1229%). Moreover, in a wet state, they enabled proper water vapor transmission rate (>2000 g/m²/day), thanks to their hydrogel structure. Finally, it was found that biomaterial composed of 11 wt.% of curdlan (Cur_11%) possessed the most desirable biological properties in vitro. It released a beneficial amount of calcium ions to the aqueous environment (approximately 6.12 mM), which significantly enhanced fibroblast viability and proliferation. Taking into account the beneficial properties of Cur_11% biomaterial, it seems justified to subject it to more advanced cell culture experiments in vitro and to in vivo studies in order to determine its precise influence on skin wound healing.

A cut above the rest: oxidative stress in chronic wounds and the potential role of polyphenols as therapeutics

OBJECTIVES

The pathophysiology of chronic wounds typically involves redox imbalance and inflammation pathway dysregulation, often with concomitant microbial infection. Endogenous antioxidants such as glutathione and tocopherols are notably reduced or absent, indicative of significant oxidative imbalance. However, emerging evidence suggests that polyphenols could be effective agents for the amelioration of this condition. This review aims to summarise the current state of knowledge surrounding redox imbalance in the chronic wound environment and the potential use of polyphenols for the treatment of chronic wounds.

KEY FINDINGS

Polyphenols provide a multi-faceted approach towards the treatment of chronic wounds. Firstly, their antioxidant activity allows direct neutralisation of harmful free radicals and reactive oxygen species, assisting in restoring redox balance. Upregulation of pro-healing and anti-inflammatory gene pathways and enzymes by specific polyphenols further acts to reduce redox imbalance and promote wound healing actions, such as proliferation, extracellular matrix deposition and tissue remodelling. Finally, many polyphenols possess antimicrobial activity, which can be beneficial for preventing or resolving infection of the wound site.

SUMMARY

Exploration of this diverse group of natural compounds may yield effective and economical options for the prevention or treatment of chronic wounds.

Superabsorbent curdlan-based foam dressings with typical hydrocolloids properties for highly exuding wound management

Effective management of chronic wounds with excessive exudate may be challenging for medical doctors. Over the years, there has been an increasing interest in the engineering of biomaterials, focusing on the development of polymer-based wound dressings to accelerate the healing of exuding wounds. The aim of this study was to use curdlan, which is known to support wound healing, as a base for the production of superabsorbent hybrid biomaterials (curdlan/agarose and curdlan/chitosan) with the intended use as wound dressings for highly exuding wound management. To evaluate the biomedical potential of the fabricated curdlan-based biomaterials, they were subjected to a comprehensive assessment of their microstructural, physicochemical, and biological properties. The obtained results showed that foam-like biomaterials with highly porous structure (66-77%) transform into soft gel after contact with the wound fluid, acting as typical hydrocolloid dressings. Novel biomaterials have the superabsorbent ability (1 g of the biomaterial absorbs approx. 15 ml of exudate) with horizontal wicking direction while keeping dry edges, and show water vapor transmission rate of approx. 1700-1800 g/m²/day which is recommended for optimal wound healing. Moreover, they are stable in the presence of collagenases, but prone to biodegradation in lysozyme solution (simulated infected wound environment). Importantly, the developed biomaterials are non-toxic and their surface hinders fibroblast attachment, which is essential during dressing changes to avoid damage to newly formed tissues in the wound bed. All mentioned features make the developed biomaterials promising candidates to be used as the wound dressings for the management of chronic wounds with moderate to high exudate.

Poly(chitosan-ester-ether-urethane) Hydrogels as Highly Controlled Genistein Release Systems

Polymeric hydrogels play an increasingly important role in medicine, pharmacy and cosmetology. They appear to be one of the most promising groups of biomaterials due to their favorable physicochemical properties and biocompatibility. The objective of the presented study was to synthesize new poly(chitosan-ester-ether-urethane) hydrogels and to study the kinetic release of genistein (GEN) from these biomaterials. In view of the above, six non-toxic hydrogels were synthesized via the Ring-Opening Polymerization (ROP) and polyaddition processes. The poly(ester-ether) components of the hydrogels have been produced in the presence of the enzyme as a biocatalyst. In some cases, the in vitro release rate of GEN from the obtained hydrogels was characterized by near-zero-order kinetics, without "burst release" and with non-Fickian transport. It is important to note that developed hydrogels have been shown to possess the desired safety profile due to lack of cytotoxicity to skin cells (keratinocytes and fibroblasts). Taking into account the non-toxicity of hydrogels and the relatively highly controlled release profile of GEN, these results may provide fresh insight into polymeric hydrogels as an effective dermatological and/or cosmetological tool.

Development of thermosensitive hydrogel wound dressing containing Acinetobacter baumannii phage against wound infections

With the emergence of multidrug resistance (MDR) bacteria, wound infection continues to be a challenging problem and represents a considerable healthcare burden. This study aims to evaluate the applicability of a phage loaded thermosensitive hydrogel in managing wound infections caused by MDR Acinetobacter baumannii, using IME-AB2 phage and MDR-AB2 as the model phage and bacteria, respectively. Excellent storage stability of the IME-AB2 phage in a ~18 wt% Poloxamer 407 (P407) hydrogel solution was first demonstrated with negligible titer loss (~0.5 log) in 24 months at 4 °C. The incorporated phage was released in a sustained manner with a cumulative release of 60% in the first 24 h. The in vitro bacterial killing efficiency of phage gel and phage suspension at 37 °C demonstrated >5 log₁₀ CFU/ml reduction against A. baumannii. A comparable biofilm elimination capacity was also noted between the phage gel and phage suspension (59% and 45% respectively). These results suggested that the incorporation of phage into the hydrogel not only had insignificant impacts on the bacterial killing efficiency of phage, but also act as a phage depot to maintain higher phage titer at the infectious site for a prolong period for more effective treatment. We also found that the hydrogel formulation significantly suppressed microbial survival in an ex vivo wound infection model using pig skin (90% reduction in bacterial counts was achieved after 4 h treatment). In summary, our results demonstrated that the P407-based phage-loaded thermosensitive hydrogel is a simple and promising phage formulation for the management of wound infections.

Alginate/poloxamer hydrogel obtained by thiol-acrylate photopolymerization for the alleviation of the inflammatory response of human keratinocytes

Hydrogel-based wound dressings have been intensively studied as promising materials for wound healing and care. The mixed-mode thiol-acrylate photopolymerization is used in this paper for alginate/poloxamer hydrogels formation. First, the alginate was modified with thiol groups using the esterification reaction with cysteamine, and second, the terminal hydroxyl groups of poloxamer were esterified with acryloyl chloride to introduce polymerizable acrylate groups. Finally, the cross-linking reaction between the two macromers was performed to produce degradable alginate/poloxamer hydrogels. The optimum conditions for the photo-initiated reaction were studied in order to obtain high gel fractions. The resulting hydrogels have high swelling capacity in simulated physiological conditions, good elasticity and strength, and appropriate porosity, some of the physico-chemical properties required for their applications as wound dressings/patches. The biological assays show that the alginate/poloxamer hydrogels induce proliferation of human keratinocyte and have an anti-inflammatory effect on lipopolysaccharides (LPS)-activated keratinocytes by inhibiting the extracellular signal-regulated kinases (ERK)/ nuclear factor (NF)-kB/ tumor necrosis factor (TNF)-α signalling pathway. Taken together, the results showed that the chemical cross-linked alginate/poloxamer hydrogels may function as a dressing/patch applied directly on the skin lesion to heal the wound by reducing the exacerbated inflammation, the main cause of wound healing delay and local infection.

Poly(Vinyl Alcohol) Cryogel Membranes Loaded with Resveratrol as Potential Active Wound Dressings

Hydrogel wound dressings are highly effective in the therapy of wounds. Yet, most of them do not contain any active ingredient that could accelerate healing. The aim of this study was to prepare hydrophilic active dressings loaded with an anti-inflammatory compound - trans-resveratrol (RSV) of hydrophobic properties. A special attention was paid to select such a technological strategy that could both reduce the risk of irritation at the application site and ensure the homogeneity of the final hydrogel. RSV dissolved in Labrasol was combined with an aqueous sol of poly(vinyl) alcohol (PVA), containing propylene glycol (PG) as a plasticizer. This sol was transformed into a gel under six consecutive cycles of freezing (-80 °C) and thawing (RT). White, uniform and elastic membranes were successfully produced. Their critical features, namely microstructure, mechanical properties, water uptake and RSV release were studied using SEM, DSC, MRI, texture analyser and Franz-diffusion cells. The cryogels made of 8 % of PVA showed optimal tensile strength (0.22 MPa) and elasticity (0.082 MPa). The application of MRI enabled to elucidate mass transport related phenomena in this complex system at the molecular (detection of PG, confinement effects related to pore size) as well as at the macro level (swelling). The controlled release of RSV from membranes was observed for 48 h with mean dissolution time of 18 h and dissolution efficiency of 35 %. All in all, these cryogels could be considered as a promising new active wound dressings.

Collagen-Carboxymethylcellulose Biocomposite Wound-Dressings with Antimicrobial Activity

Microbial infections associated with skin diseases are frequently investigated since they impact on the progress of pathology and healing. The present work proposes the development of freeze-dried, glutaraldehyde cross-linked, and non-cross-linked biocomposite dressings with a porous structure, which may assist the reepithelization process through the presence of collagen and carboxymethylcellulose, along with a therapeutic antimicrobial effect, due to silver nanoparticles (AgNPs) addition. Phisyco-chemical characterization revealed the porous morphology of the obtained freeze-dried composites, the presence of high crystalline silver nanoparticles with truncated triangular and polyhedral morphologies, as well as the characteristic absorption bands of collagen, silver, and carboxymethylcellulose. In vitro tests also assessed the stability, functionality, and the degradability rate of the obtained wound-dressings. Antimicrobial assay performed on Gram-negative (Escherichia coli), Gram-positive (Staphyloccocus aureus) bacteria, and yeast (Candida albicans) models demonstrated that composite wound dressings based on collagen, carboxymethylcellulose, and AgNPs are suitable for skin lesions because they prevent the risk of infection and have prospective wound healing capacity. Moreover, the cell toxicity studies proved that the obtained materials can be used in long time treatments, with no cytotoxic effects.

Recent advances on polymeric hydrogels as wound dressings

Severe hemorrhage is a leading cause of high mortality in critical situations like disaster, accidents, and warfare. The resulting wounds could induce severe physical and psychological trauma to patients and also bring an immense socio-economic burden. Hence, rapid hemostasis and wound healing techniques have become critical initiatives for life-saving treatment. Although traditional methods relying on bandages and gauzes are effective in controlling hemorrhage, they suffer from several limitations: nonbiodegradability, being susceptible to infection, being unsuitable for the irregular wound, secondary tissue damage, and being almost ineffective for wound healing. Owing to the merits of high porosity, good biocompatibility, tunable physicochemical properties, and being beneficial for wound healing, hydrogels with excellent performance have drawn intensive attention and numerous novel effective hydrogel dressings have been widely developed. In this Review, after introducing some commonly used strategies for the synthesis of hydrogels, the most recent progress on polymer-based hydrogels as wound dressings is discussed. Particularly, their hemostasis, antibacterial, and biodegradation properties are introduced. Finally, challenges and future perspectives about the development of hydrogels for wound dressings are outlined.

New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for Ni^II , Co^II and Cu^II compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1-5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.

Wear Behavior Characterization of Hydrogels Constructs for Cartilage Tissue Replacement

This paper aims to characterize the wear behavior of hydrogel constructs designed for human articular cartilage replacement. To this purpose, poly (ethylene glycol) diacrylate (PEGDA) 10% w/v and gellan gum (GG) 1.5% w/v were used to reproduce the superior (SUP) cartilage layer and PEGDA 15% w/v and GG 1.5% w/v were used to reproduce the deep (DEEP) cartilage layer, with or without graphene oxide (GO). These materials (SUP and DEEP) were analyzed alone and in combination to mimic the zonal architecture of human articular cartilage. The developed constructs were tested using a four-station displacement control knee joint simulator under bovine calf serum. Roughness and micro-computer tomography (µ-CT) measurements evidenced that the hydrogels with 10% w/v of PEGDA showed a worse behavior both in terms of roughness increase and loss of uniformly distributed density than 15% w/v of PEGDA. The simultaneous presence of GO and 15% w/v PEGDA contributed to keeping the hydrogel construct's characteristics. The Raman spectra of the control samples showed the presence of unreacted C=C bonds in all the hydrogels. The degree of crosslinking increased along the series SUP < DEEP + SUP < DEEP without GO. The Raman spectra of the tested hydrogels showed the loss of diacrylate groups in all the samples, due to the washout of unreacted PEGDA in bovine calf serum aqueous environment. The loss decreased along the series SUP > DEEP + SUP > DEEP, further confirming that the degree of photo-crosslinking of the starting materials plays a key role in determining their wear behavior. μ-CT and Raman spectroscopy proved to be suitable techniques to characterize the structure and composition of hydrogels.

A convenient approach by using poly-(HEMA-co-NIPAM)/Cu2+ solution sol-gel transition for wound protection and healing

Rapid and convenient wound healing is crucial for reducing potential post-traumatic wound complications. In this study, a temperature-sensitive polymer of poly-(HEMA-co-NIPAM) (PHN) was synthesized by free-radical polymerization, in which the solution quickly underwent a sol-gel transition above 29°C, thus responding to a typical body temperature and facilitating wound sealing. PHN solution incorporated with copper ions (PHN-Cu) not only exhibited excellent antibacterial properties, but also expedited wound closure and facilitated tissue angiogenesis. The in vivo and in vitro experiments showed that the PHN-Cu had a higher wound closure rate and demonstrated an ability to promote skin tissue angiogenesis. Such a versatile, convenient aqueous solution could enable nonprofessionals to promptly treat wounds in a short time after injury, thus providing suitable conditions for later treatment, and can be used as a convenient method to clean wounds.

Hydrogels containing soybean isoflavone aglycones-rich fraction-loaded nanoemulsions for wound healing treatment - in vitro and in vivo studies

Soybean isoflavone aglycones have been investigated as potential wound healing compounds for topical application. The aim of this study was to evaluate the wound healing properties of a soybean isoflavone aglycones-rich fraction (IAF) when incorporated into lipid nanoemulsions dispersed in acrylic-acid hydrogels. Formulations exhibited a mean droplet size in the sub 200 nm range, negative ζ-potential (-60 mV), and displayed non-Newtonian pseudoplastic behavior. The addition of a gelling agent decreased the IAF release from formulations and improved the retention of these compounds in intact porcine ear skin when compared with a control propylene glycol solution. No IAF were detected in receptor fluid of Franz-type diffusion cells. However, increasing amounts of IAF were noticed in both skin layers and the receptor fluid when the tissue was partially injured (tape stripping), or when the epidermis was completely removed. In vitro studies showed that IAF elicits an increased proliferation and migration of keratinocytes (HaCaT cell line). Subsequently, the healing effect of the formulations was evaluated in a model of dorsal wounds in rats, by assessing the size of the lesions, histology, inflammatory markers, and antioxidant activity. Overall findings demonstrated the potential of IAF-loaded formulations to promote wound healing by increasing angiogenesis by ∼200 %, reducing the lipid oxidation (TBARS) by ∼52 % and the inflammation (TNFα) by ∼35 %, while increasing re-epithelialization by ∼500 %, visualized by the epithelium thickness.

Forward Wound Closure with Regenerated Silk Fibroin and Polylysine-Modified Chitosan Composite Bioadhesives as Dressings

Wound dressing has been used for decades to be effective for accelerating skin wound healing. However, practical applications are still limited due to their lower cell affinity, tissue adhesiveness, and biocompatibility. Natural polymers are the important biomaterials because of their excellent biodegradability, biocompatibility, and low immunogenicity. In this work, the composite bioadhesives (PLS-CS/RSF) were prepared from regenerated silk fibroin (RSF) and polylysine-modified chitosan (PLS-CS) that were cross-linked by Ca²⁺ ions. The adhesion property tests showed that the PLS-CS/RSF exhibited excellent bonding potentials for various substrates, and the adhesive strength was up to 70 kPa for isolated porcine skin by the extension test. The as-prepared PLS-CS/RSF was nontoxic, displayed obvious antibacterial effects against Staphylococcus aureus and Escherichia coli in vitro, and their bacteriostasis rates were 100% after 120 min treatment. In addition, the PLS-CS/RSF exhibited favorable cytocompatibility by cell counting kit-8 assay. The animal model of wound closure results showed that PLS-CS/RSF can promote wound closure and the integrity of wound healing, inhibiting the secretion of inflammatory factor and tumor necrosis factor and stimulating vascular factor and α-smooth muscle actin to the release of vascular growth factor and promote angiogenesis during the process of wound healing by immunohistochemical assay.

Preparation and Evaluation of Collagen-Based Patches as Curcumin Carriers

Patients with psoriasis are dissatisfied with the standard pharmacological treatments, whether systemic or topical, with many of them showing interest in complementary and alternative medicine. Curcumin (Cur), a natural polyphenol derived from turmeric, has recently gained attention for skin-related diseases because of its proven anti-inflammatory action. However, topical treatment with Cur would be inadequate because of its hydrophobicity, instability, and low bioavailability. In addition, hyperkeratosis and lack of moisture in psoriatic skin result in low penetration that would prevent actives from permeating the stratum corneum. In this work, a polymer-based formulation of Cur for the topical treatment of psoriasis is reported. To improve the physicochemical stability of Cur, it was first encapsulated in chitosan nanoparticles. The Cur-loaded nanoparticles were incorporated in a hydrophilic, biocompatible collagen-based patch. The nanoparticle-containing porous collagen patches were then chemically cross-linked. Morphology, chemical interactions, swelling ratio, enzymatic hydrolysis, and Cur release from the patches were evaluated. All patches showed excellent swelling ratio, up to ~1500%, and after cross-linking, the pore size decreased, and their hydrolysis rates decelerated. The in vitro release of Cur was sustained with an initial burst release, reaching 55% after 24 h. Cur within the scaffolds imparted a proliferation inhibitory effect on psoriatic human keratinocytes in vitro.

Cellulose Nanocomposite Hydrogels: From Formulation to Material Properties

Poly(vinyl alcohol) (PVA) hydrogels produced using the freeze-thaw method have attracted attention for a long time since their first preparation in 1975. Due to the importance of polymer intrinsic features and the advantages associated with them, they are very suitable for biomedical applications such as tissue engineering and drug delivery systems. On the other hand, there is an increasing interest in the use of biobased additives such as cellulose nanocrystals, CNC. This study focused on composite hydrogels which were produced by using different concentrations of PVA (5 and 10%) and CNC (1 and 10 wt.%), also, pure PVA hydrogels were used as references. The main goal was to determine the impact of both components on mechanical, thermal, and water absorption properties of composite hydrogels as well as on morphology and initial water content. It was found that PVA had a dominating effect on all hydrogels. The effect of the CNC addition was both concentration-dependent and case-dependent. As a general trend, addition of CNC decreased the water content of the prepared hydrogels, decreased the crystallinity of the PVA, and increased the hydrogels compression modulus and strength to some extent. The performance of composite hydrogels in a cyclic compression test was studied; the hydrogel with low PVA (5) and high CNC (10) content showed totally reversible behavior after 10 cycles.

Novel Eco-Friendly Tannic Acid-Enriched Hydrogels-Preparation and Characterization for Biomedical Application

Sodium alginate and tannic acid are natural compounds that can be mixed with each other. In this study, we propose novel eco-friendly hydrogels for biomedical applications. Thus, we conducted the following assessments including (i) observation of the structure of hydrogels by scanning electron microscope; (ii) bioerosion and the concentration of released tannic acid from subjected material; (iii) dehydrogenase activity assay to determine antibacterial activity of prepared hydrogels; and (iv) blood and cell compatibility. The results showed that hydrogels based on sodium alginate/tannic acid exert a porous structure. The immersion in simulated body fluid (SBF) results in the biomineralization process occurring on their surface while the bioerosion studies revealed that the addition of tannic acid improves hydrogels’ stability proportional to its concentration. Besides, tannic acid release concentration depends on the type of hydrogels and the highest amount was noticed for those based on sodium alginate with the content of 30% tannic acid. Antibacterial activity of hydrogels was proven for both Gram-negative and Gram-positive bacteria, the hemolysis rate was below 5% and the viability of the cells was elevated with an increasing amount of tannic acid in hydrogels. Collectively, we assume that obtained materials make the imperative to consider them for biomedical applications.

Regenerative Wound Dressings for Skin Cancer

Skin cancer is considered the most prevalent cancer type globally, with a continuously increasing prevalence and mortality growth rate. Additionally, the high risk of recurrence makes skin cancer treatment among the most expensive of all cancers, with average costs estimated to double within 5 years. Although tumor excision is the most effective approach among the available strategies, surgical interventions could be disfiguring, requiring additional skin grafts for covering the defects. In this context, post-surgery management should involve the application of wound dressings for promoting skin regeneration and preventing tumor recurrence and microbial infections, which still represents a considerable clinical challenge. Therefore, this paper aims to provide an up-to-date overview regarding the current status of regenerative wound dressings for skin cancer therapy. Specifically, the recent discoveries in natural biocompounds as anti-cancer agents for skin cancer treatment and the most intensively studied biomaterials for bioactive wound dressing development will be described.

Enhancement of α-Mangostin Wound Healing Ability by Complexation with 2-Hydroxypropyl-β-Cyclodextrin in Hydrogel Formulation

α-Mangostin (α-M), one of the active compounds in Garcinia mangostana peel, has been effectively used in wound healing. However, its poor solubility in aqueous solution causes low bioavailability for skin ulcers, hindering its application in wound healing. The aim of this study was to improve the solubility of α-M through complex formation with 2-hydroxypropyl-β-cyclodextrin (α-M/HP-β-CD CX) and to evaluate the healing activity of the complex. The α-M/HP-β-CD CX was incorporated in a sodium carboxymethylcellulose hydrogel (α-M/HP-β-CD CX HG), and the in vivo healing activity was examined in mice. Evaluation of α-M/HP-β-CD CX HG, including organoleptic evaluation, homogeneity, pH, spreadability, swelling ratio, consistency, scanning electron microscopy (SEM), and in vitro drug release, was carried out. The complex formation of α-M/HP-β-CD CX was confirmed by FTIR and PXRD analysis. The solubility of the α-M/HP-β-CD CX in water linearly increased about 11.7-fold compared to α-M alone, and by 3.5-fold compared to the α-M/HP-β-CD physical mixture (α-M/HP-β-CD CX PM). The α-M/HP-β-CD CX HG was homogenous, the pH was found to be in the neutral range, the spread area was 5 cm, and the consistency was stable until 14 days. SEM analysis showed that α-M/HP-β-CD CX HG surged due to the porous structure of the HG. In addition, in vitro release of α-M from α-M/HP-β-CD CX HG was considerably increased compared to α-M/HP-β-CD PM HG and α-M HG. Notably, in vivo evaluation in mice showed that α-M/HP-β-CD CX HG significantly accelerated the wound healing ability compared to other HGs. Thus, α-M/HP-β-CD CX HG has potential as a new formulation of α-M for wound healing therapy.

A Review on Revolutionary Natural Biopolymer-Based Aerogels for Antibacterial Delivery

A biopolymer-based aerogel has been developed to become one of the most potentially utilized materials in different biomedical applications. The biopolymer-based aerogel has unique physical, chemical, and mechanical properties and these properties are used in tissue engineering, biosensing, diagnostic, medical implant and drug delivery applications. Biocompatible and non-toxic biopolymers such as chitosan, cellulose and alginates have been used to deliver antibiotics, plants extract, essential oils and metallic nanoparticles. Antibacterial aerogels have been used in superficial and chronic wound healing as dressing sheets. This review critically analyses the utilization of biopolymer-based aerogels in antibacterial delivery. The analysis shows the relationship between their properties and their applications in the wound healing process. Furthermore, highlights of the potentials, challenges and proposition of the application of biopolymer-based aerogels is explored.

Alginate hydrogel containing hydrogen sulfide as the functional wound dressing material: In vitro and in vivo study

Functional and bioactive wound dressing materials are revolutionary for wound care and healing applications. In this concept, we fabricated alginate hydrogel (Alg) containing H₂S as the wound dressing materials and assessed the morphology, swelling, degradation, and release behavior, as well as the biocompatibility, cytocompatibility, and wound healing activity. The results depicted that the prepared hydrogels have a porous structure with the pore size in the range of 50 to 100 μm. Swelling and degradation studies showed that the hydrogel absorbed water about 179 ± 5% of initial dry weight during 96 h and loos about 80% of the initial dry weight after 7 days. The in vitro assessments illustrated that the optimum concentration of H₂S was 0.5% and the higher concentration induced hemolysis and cell toxicity. The in vivo study revealed that the treatment by Alg/H₂S 0.5% induced the highest wound closure percent with a value of 98 ± 1.22%. Moreover, the treatment by Alg/H₂S 0.5% elicited the formation of sebaceous glands, hair follicles, and complete epithelization without any fibroplasia or inflammation, revealed by the histopathological observations. Accordingly, these results illustrated that the prepared Alg/H₂S 0.5% could be applied as the functional and bioactive wound dressing materials.

Porous Curdlan-Based Hydrogels Modified with Copper Ions as Potential Dressings for Prevention and Management of Bacterial Wound Infection-An In Vitro Assessment

Bacterial infections at the wound site still remain a huge problem for current medicine, as they may lead to development of chronic wounds. In order to prevent such infections, there is a need to use wound dressings that possess ability to inhibit bacterial colonization. In this study, three new curdlan-based biomaterials modified with copper ions were fabricated via simple and inexpensive procedure, and their structural, physicochemical, and biological properties in vitro were evaluated. Received biomaterials possessed porous structure, had ability to absorb high amount of simulated wound fluid, and importantly, they exhibited satisfactory antibacterial properties. Nevertheless, taking into account all evaluated properties of new curdlan-based biomaterials, it seems that Cur_Cu_8% is the most promising biomaterial for management of wounds accompanied with bacterial infections. This biomaterial exhibited the best ability to reduce Escherichia coli and Staphylococcus aureus growth and moreover, it absorbed the highest amount of simulated wound fluid as well as enabled optimal water vapor transmission. Furthermore, Cur_Cu_8% biomaterial possessed the best values of selective indexes, which determine its potential safety in vitro. Thus, Cur_Cu_8% hydrogel may be considered as a promising candidate for management of infected wounds as well as it may constitute a good platform for further modifications.

Advanced Hydrogels as Wound Dressings

Skin is the largest organ of the human body, protecting it against the external environment. Despite high self-regeneration potential, severe skin defects will not heal spontaneously and need to be covered by skin substitutes. Tremendous progress has been made in the field of skin tissue engineering, in recent years, to develop new skin substitutes. Among them, hydrogels are one of the candidates with most potential to mimic the native skin microenvironment, due to their porous and hydrated molecular structure. They can be applied as a permanent or temporary dressing for different wounds to support the regeneration and healing of the injured epidermis, dermis, or both. Based on the material used for their fabrication, hydrogels can be subdivided into two main groups—natural and synthetic. Moreover, hydrogels can be reinforced by incorporating nanoparticles to obtain “in situ” hybrid hydrogels, showing superior properties and tailored functionality. In addition, different sensors can be embedded in hydrogel wound dressings to provide real-time information about the wound environment. This review focuses on the most recent developments in the field of hydrogel-based skin substitutes for skin replacement. In particular, we discuss the synthesis, fabrication, and biomedical application of novel “smart” hydrogels.

Catechol modified quaternized chitosan enhanced wet adhesive and antibacterial properties of injectable thermo-sensitive hydrogel for wound healing

Wound dressings based on injectable thermo-sensitive hydrogel possess several advantages over preformed conventional dressings such as rapid reversible sol-gel transition behavior and the capacity of filling the irregular wound defect. Nevertheless, its clinical application is hindered by the weak tissue adhesiveness. Therefore, in this study, the catechol modified quaternized chitosan (QCS-C) was fabricated and incorporated into poly(d,l-lactide)-poly(ethylene glycol)-poly(d,l-lactide) (PLEL) hydrogel to develop an injectable hydrogel with the properties of thermo-sensitive, antibacterial and tissue adhesive. QCS-C could lower the LCST of hydrogel for easy gelation at physiological temperature, and significantly enhanced the tissue adhesion. For wound generation, nano-scaled bioactive glass (nBG：80 SiO₂, 16 CaO and 4 P₂O₅; mol%) was loaded into hydrogel to promote angiogenesis. The mice partial laceration experiment showed that PLEL-nBG-QCS-C hydrogel could effectively seal the ruptured skin and significantly accelerate wound healing. Thus, our findings established a new type of clinical treatment technology for complicated wounds.

Natural Polymer-Based Antimicrobial Hydrogels without Synthetic Antibiotics as Wound Dressings

Wound healing is usually accompanied by bacterial infection. The excessive use of synthetic antibiotics leads to drug resistance, posing a significant threat to human health. Hydrogel-based wound dressings aimed at mitigating bacterial infections have emerged as an effective wound treatment. The review presented herein particularly focuses on the hydrogels originating from natural polymers. To further enhance the performance of wound dressings, various strategies and approaches have been developed to endow the hydrogels with excellent broad-spectrum antibacterial activity. Those that are summarized in the current review are the hydrogels with intrinsic or stimuli-triggered bactericidal properties and others that serve as vehicles for loading antibacterial agents without synthetic antibiotics. Specific attention is paid to antimicrobial mechanisms and the antibacterial performance of hydrogels. Practical antibacterial applications to accelerate the wound healing employing these antibiotic-free hydrogels are also introduced along with the discussion on the current challenges and perspectives leading to new technologies.

Degradable Hydrogels for the Delivery of Immune-modulatory Proteins in the Wound Environment

Chronic wounds represent a growing clinical problem for which limited treatment strategies exist. Defects in immune cell-mediated healing play an important role in chronic wound development, presenting an attractive clinical target in the treatment of chronic wounds. However, efforts to improve healing through the application of growth factors and cytokines have been limited by the rapid degradation and diffusion of these molecules in the wound environment. In this study we sought to overcome the challenge of rapid diffusion through the development of a hydrogel delivery system in which protein cargo can be released into the wound environment at a constant and tunable rate. This system was used to deliver the intercellular adhesion molecule-1 (ICAM-1) in order to target endogenous cells upstream of growth factor and cytokine production and circumvent the issue of their rapid degradation. We demonstrated that our delivery system was able to release cargo at different and highly controllable rates and thereby improved cargo retention in the wound environment. Additionally, treatment with ICAM-1 in the delivery system improved healing in both ICAM-1-deficient mice and an aged mouse model of delayed healing, highlighting a potential clinical benefit for this protein in the treatment of chronic wounds.

Evaluation of wound healing effect of alginate film containing Aloe vera gel and cross-linked with zinc chloride

PURPOSE

To develop a new wound dressing composed of alginate and Aloe vera gel and cross-linked with zinc ions.

METHODS

The aloe-alginate film was characterized using scanning electron microscopy (SEM), swelling profile, mechanical properties, polysaccharide content and X-ray diffraction (XRD). Thirty Wistar rats were divided in two groups a) treated with aloe-alginate film and b) control (treated with sterile gauze). Wound contraction measurements and hystological analysis were performed on 7th, 14th and 21st days after wound surgery.

RESULTS

The aloe-alginate film presented adequated mechanical resistance and malleability for application as wound dressing. There was no statistical difference in wound contraction between two groups. Histological assay demonstrated that aloe-alginate film presented anti-inflammatory activity, stimulated angiogenesis on proliferative phase and a more significant increased in collagen type I fibers and decreased type III fibers which promoted a mature scar formation when compared to control.

CONCLUSIONS

The aloe-alginate film showed adequate physicochemical characteristics for wound dressing applications. The in vivo assay demonstrated that aloe-alginate film enhanced the healing process of incisional skin wounds.

Topical delivery of growth factors and metal/metal oxide nanoparticles to infected wounds by polymeric nanoparticles: an overview

INTRODUCTION

Infected chronic wounds particularly diabetic foot ulcers (DFUs) can result from stable colonization of antibiotic-resistant bacteria and fungi at the wound sites. In this context, the rapid healing of infected wounds has been the main goal in recent investigations. This issue can be solved by improving wound-healing phases including hemostasis, inflammatory, proliferative, and remodeling/maturation, and removal of bacteria and fungi. The applications of growth factors (GFs) and metal/metal oxide nanoparticles (MNPs/MONPs) are two choices for these targets. However, the lack of sustainable release of these agents is an important problem for appropriate wound healing.

AREA COVERED

The present review is focused on recent advances in delivery systems composed of growth factor and MNPs/MONPs for rapid wound healing.

EXPERT OPINION

Synthetic and natural polymeric micro- and nanocarriers including polyvinylpyrrolidone (PVP) and chitosan play a vital role in the healing of infected chronic wounds. Using various derivatives of chitosan as pH-responsive polymer with basic and acidic groups can be the best option to prepare controllable and sequential GF release. However, it warrants further extensive research to solve wound-healing problems.

Hydrogel Dressings for the Treatment of Burn Wounds: An Up-To-Date Overview

Globally, the fourth most prevalent devastating form of trauma are burn injuries. Ideal burn wound dressings are fundamental to facilitate the wound healing process and decrease pain in lower time intervals. Conventional dry dressing treatments, such as those using absorbent gauze and/or absorbent cotton, possess limited therapeutic effects and require repeated dressing changes, which further aggravate patients' suffering. Contrariwise, hydrogels represent a promising alternative to improve healing by assuring a moisture balance at the burn site. Most studies consider hydrogels as ideal candidate materials for the synthesis of wound dressings because they exhibit a three-dimensional (3D) structure, which mimics the natural extracellular matrix (ECM) of skin in regard to the high-water amount, which assures a moist environment to the wound. There is a wide variety of polymers that have been used, either alone or blended, for the fabrication of hydrogels designed for biomedical applications focusing on treating burn injuries. The aim of this paper is to provide an up-to-date overview of hydrogels applied in burn wound dressings.

Nanomaterials for Wound Dressings: An Up-to-Date Overview

As wound healing continues to be a challenge for the medical field, wound management has become an essential factor for healthcare systems. Nanotechnology is a domain that could provide different new approaches concerning regenerative medicine. It is worth mentioning the importance of nanoparticles, which, when embedded in biomaterials, can induce specific properties that make them of interest in applications as materials for wound dressings. In the last years, nano research has taken steps to develop molecular engineering strategies for different self-assembling biocompatible nanoparticles. It is well-known that nanomaterials can improve burn treatment and also the delayed wound healing process. In this review, the first-line of bioactive nanomaterials-based dressing categories frequently applied in clinical practice, including semi-permeable films, semipermeable foam dressings, hydrogel dressings, hydrocolloid dressings, alginate dressings, non-adherent contact layer dressings, and multilayer dressings will be discussed. Additionally, this review will highlight the lack of high-quality evidence and the necessity for future advanced trials because current wound healing therapies generally fail to provide an excellent clinical outcome, either structurally or functionally. The use of nanomaterials in wound management represents a unique tool that can be specifically designed to closely reflect the underlying physiological processes in tissue repair.

In situ hydrogel dressing loaded with heparin and basic fibroblast growth factor for accelerating wound healing in rat

In order to accelerate the healing of chronic wound, a hydrogel dressing encapsulating with heparin and basic fibroblast growth factor is prepared by the Michael addition of 4-arm acrylated polyethylene glycol and dithiothreitol. As-prepared hydrogel dressing can combine the advantages of wet healing theory and exogenous growth factor supplement. Furthermore, the encapsulated heparin can play a role in diminishing inflammation and accelerating wound healing in addition to its well-known function of stabilizing basic fibroblast growth factor. In vitro release test shows the hydrogel network is able to sustainably release basic fibroblast growth factor within 10 days by the regulation of heparin, while released growth factor can significantly promote fibroblast's proliferation in vitro. Moreover, the wound healing in rat shows that as-prepared hydrogel dressing could accelerate wound healing in vivo much more effectively compared with blank hydrogel dressing and negative control. Hematoxylin-eosin and Masson's Trichrome staining exhibit the formation of complete and uniform epidermis. Immunohistochemical staining exhibits heparin can help hydrogel dressing to possess low inflammation in early stage, which is beneficial for accelerating wound healing as well as preventing the production of scar tissue. The enzyme-linked immunosorbent assay results demonstrate the exogenous bFGF in hydrogel can significantly upgrade the expressing of vascular endothelial growth factor and transforming growth factor-β in wound site, which indicate better angiogenesis, and better on-site cell proliferation in wound site, respectively. Those results are further demonstrated by immunohistochemical and immunofluorescence staining. Consequently, as-prepared hydrogel dressing shows promising potential to perform better therapy efficacy in clinic for accelerating wound healing.

Chitosan based hydrogels and their use in medicine

Chitosan is a natural biopolymer, polysaccharide, a product of chitin deacetylation. Chitosan is a non-toxic, biocompatible and biodegradable polymer with high biological activity and stability in the environment. In addition, chitosan is obtained from natural renewable resources and is an inexpensive substance. Due to all these properties, chitosan is widely used in practical medicine, for example, in the form of hydrogel dosage forms in combination with natural and synthetic polymers. This review is focused on polymer hydrogel materials based on chitosan. Special attention is paid to the preparation and use of wound dressings for the treatment of wounds of various etiologies. The use of hydrogel wound dressings based on this polysaccharide allows to create a protective shell on the surface of various wounds, to prolong delivery of antibacterial agents, peptides and other active substances, which significantly increases the effectiveness of therapy. Bactericidal and sorption properties of chitosan-based hydrogels established in experimental and clinical studies are discussed.

Conformable hyaluronic acid hydrogel delivers adipose-derived stem cells and promotes regeneration of burn injury

Injury to the skin from severe burns can cause debilitating physical and psychosocial distress to the patients. Upon healing, deep dermal burns often result in devastating hypertrophic scar formation. For many decades, stem cell-based therapies have shown significant potential in improving wound healing. However, current cell delivery methods are often insufficient to maintain cell viability in a harmful burn wound environment to promote skin regeneration. In this study, we developed an enhanced approach to deliver adipose-derived stem cells (ASCs) for the treatment of burn wounds, using an in-situ-formed hydrogel system comprised of a hyperbranched poly(ethylene glycol) diacrylate (HB-PEGDA) polymer, a commercially available thiol-functionalized hyaluronic acid (HA-SH) and a short RGD peptide. Stable hydrogels with tunable swelling and mechanical properties form within five minutes under physiological conditions via the Michael-type addition reaction. Combining with RGD peptide, as a cell adhesion motif, significantly alters the cellular morphology, enhances cell proliferation, and increases the paracrine activity of angiogenesis and tissue remodeling growth factors and cytokines. Bioluminescence imaging of luciferase⁺ ASCs indicated that the hydrogel protected the implanted cells from the harmful wound environment in burns. Hydrogel-ASC treatment significantly enhanced neovascularization, accelerated wound closure and reduced the scar formation. Our findings suggest that PEG-HA-RGD-based hydrogel provides an effective niche capable of augmenting the regenerative potential of ASCs and promoting burn wound healing. STATEMENT OF SIGNIFICANCE: Burn injury is one of the most devastating injures, and patients suffer from many complications and post-burn scar formation despite modern therapies. Here, we designed a conformable hydrogel-based stem cell delivery platform that allows rapid in-situ gelation upon contact with wounds. Adipose-derived stem cells were encapsulated into a PEG-HA-RGD hydrogels. Introducing of RGD motif significantly improved the cellular morphology, proliferation, and secretion of angiogenesis and remodeling cytokines. A deep second-degree burn murine model was utilized to evaluate in-vivo cell retention and therapeutic effect of the hydrogel-ASC-based therapy on burn wound healing. Our hydrogel remarkably improved ASCs viability in burn wounds and the hydrogel-ASC treatment enhanced the neovascularization, promoted wound closure, and reduced scar formation.

Hydrogel-Based Active Substance Release Systems for Cosmetology and Dermatology Application: A Review

Hydrogels are playing an increasingly important role in medicine and pharmacy. Due to their favorable physicochemical properties, biocompatibility, and designed interaction with living surroundings, they seem to be one of the most promising groups of biomaterials. Hydrogel formulations from natural, semi, or synthetic polymeric materials have gained great attention in recent years for treating various dermatology maladies and for cosmetology procedures. The purpose of this review is to present a brief review on the basic concept of hydrogels, synthesis methods, relevant mechanisms, and applications in dermatology or cosmetology. This review discusses transdermal therapies and the recent advances that have occurred in the field.

Continuous production of antibacterial carboxymethyl chitosan-zinc supramolecular hydrogel fiber using a double-syringe injection device

Large-scale production of an antibacterial hydrogel is of critical importance for its practical application in biomedical field. In this regard, herein we report on the construction of a double-syringe injection device by using all the commercial parts and its use for continuous production of carboxymethyl chitosan-zinc (CMCh-Zn) supramolecular hydrogel fiber. The resultant CMCh-Zn hydrogel fibers exhibit good stretchability and knittability. The Zn loading into the hydrogel fibers can be easily controlled by adjusting the concentration of Zn²⁺ solution. Scanning electron microscope measurements indicate that the CMCh-Zn hydrogel fibers have a relatively smooth and thin skin layer, as well as, a 3-dimensional interconnected microporous interior architecture. Antibacterial activities of the CMCh-Zn hydrogel fibers against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are also investigated. The results show that the intrinsic blue fluorescence of the as-prepared CMCh-Zn hydrogel fibers can be employed as optical indicator of their antibacterial effectiveness.

Modulating cationicity of chitosan hydrogel to prevent hypertrophic scar formation during wound healing

It is of great clinical significance to design wound dressing materials with combined excellent wound healing properties and superior capability to suppress hypertrophic scar formation. This study aimed to examine if and how the cationicity of chitosan would affect the hypertrophic scar-related outcomes, through preparing carboxymethyl chitosan hydrogels with different genipin concentrations (2.5%, 5%, 10% and 15%, respectively). An optimum window of chitosan cationicity (5% in our case) demonstrated potential to mitigate hypertrophic scar in wound healing by suppressing the expression of a-smooth muscle actin (a-SMA) and promoting secretion of type I matrix metalloproteinases (MMP-1). In vivo, the CMCS-5% hydrogel again showed smaller, thinner and smoother wound appearance. Moreover, the CMCS-5% sample with additional incorporation of 2% (V/V) Aloe vera gel exhibited further improved performance in scar inhibition. Overall, such findings might have important implications in chitosan-based wound dressing design for high-quality wound repair and effective scar inhibition.

Advances and Impact of Antioxidant Hydrogel in Chronic Wound Healing

The accelerating and thorough treatment of chronic wounds still represents a major unmet medical need owing to the complex symptoms resulting from metabolic disorder of the wound microenvironment. Although numerous strategies and bioactive hydrogels are developed, an effective and widely used method of chronic wound treatment remains a bottleneck. With the aim to accelerate chronic wound healing, many hydrogel dressings with antioxidant functions have emerged and are proven to accelerate wound healing, especially for chronic wound repair. The new strategy in chronic wound treatment brought by antioxidant hydrogels is of great significance to human health. Here, the application of antioxidant hydrogels in the repair of chronic wounds is discussed systematically, aiming to provide an important theoretical reference for the further breakthrough of chronic wound healing.