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

CO2-Mediated Alkali-Neutralization Curdlan Hydrogels for Potential Wound Healing Application

Physical hydrogels of natural polysaccharides are considered as ideal candidates for wound dressing due to their natural biological activity and no harmful cross-linking agents. However, it remains a challenge to fabricate such hydrogel dressings in a facile and low-cost way. Herein, we reported an easy and cost-effective method to construct CO2-mediated alkali-neutralization Curdlan (CR) hydrogels without using an external cross-linking agent. Two types of hydrogels (denoted as CR-NaOH and CR-Na3PO4, respectively) were fabricated by dissolving CR powders in a NaOH or Na3PO4 aqueous solution, followed by keeping the CR alkaline solutions in air. The obtained pure CR hydrogels possessed a tunable porous structure with walls containing different forms of nanofibrils. These hydrogels exhibited much higher gel strength by comparison with the gels prepared by conventional heating treatment. They were flexible, stretchable, twistable, and conformable to arbitrarily curved skins. Moreover, they exhibited ideal swellability, proper degradability, and water vapor transmission rate, and their physicochemical properties were closely related to CR concentration in the alkaline solution. These two hydrogels also supported the growth of L929 cells. Importantly, studies on wound healing revealed that both 3CR-NaOH and 3CR-Na3PO4 hydrogels were capable of accelerating the wound healing process through recruiting more macrophages/fibroblasts, inducing more collagen deposition and neovascularization (α-SMA and CD31) without carrying any exogenous bioactive components. In conclusion, the present work not only reported promising materials for application in wound therapy but also offered a facile and safe manufacturing procedure for generating pure CR physical hydrogels with better performance.

Antibacterial and antioxidant bifunctional hydrogel based on hyaluronic acid complex MoS2-dithiothreitol nanozyme for treatment of infected wounds

Wound repair is a complex physiological process that often leads to bacterial infections, which significantly threaten human health. Therefore, developing wound-healing materials that promote healing and prevent bacterial infections is crucial. In this study, the coordination interaction between sulfhydryl groups on dithiothreitol (DTT) and MoS2 nanosheets is investigated to synthesize a MoS2-DTT nanozyme with photothermal properties and an improved free-radical scavenging ability. Double-bond-modified hyaluronic acid is used as a monomer and is cross-linked with a PF127-DA agent. PHMoD is prepared in coordination with MoS2-DTT as the functional component. This hydrogel exhibits antioxidant and antibacterial properties, attributed to the catalytic activity of catalase-like enzymes and photothermal effects. Under the near-infrared (NIR), it exhibits potent antibacterial effects against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli), achieving bactericidal rates of 99.76% and 99.42%, respectively. Furthermore, the hydrogel exhibits remarkable reactive oxygen species scavenging and antioxidant capabilities, effectively countering oxidative stress in L929 cells. Remarkably, in an animal model, wounds treated with the PHMoD(2.0) and NIR laser heal the fastest, sealing completely within 10 days. These results indicate the unique biocompatibility and bifunctionality of the PHMoD, which make it a promising material for wound-healing applications.

Recent innovations (2020-2023) in the approaches for the chemical functionalization of curdlan and pullulan: A mini-review

Chemical modification represents a highly efficacious approach for enhancing the physicochemical characteristics and biological functionalities of natural polysaccharides. However, not all polysaccharides have considerable pharmacologic activity; so, appropriate chemical modification strategies can be selected in accordance with the distinct structural properties of polysaccharides to aid in improving and encouraging the presentation of their biological activities. Hence, there has been a growing interest in the chemical alteration of polysaccharides due to their various properties such as antioxidant, anticoagulant, antiviral, anticancer, biomedical, antibacterial, and immunomodulatory effects. This paper offers a comprehensive examination of recent scientific advancements produced over the past four years in the realm of unique chemical and functional modifications in curdlan and pullulan structures. This review aims to provide readers with an overview of the structural activity correlations observed in the backbone structures of curdlan and pullulan, as well as the diverse chemical modification processes employed for these polysaccharides. Additionally, the review aims to examine the effects of combining various bioactive molecules with chemically modified curdlan and pullulan and explore their potential applications in various important fields.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor β, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

Antibacterial and biofilm-inhibiting cotton fabrics decorated with copper nanoparticles grown on graphene nanosheets

Infectious pathogens can be transmitted through textiles. Therefore, additional efforts are needed to develop functional fabrics containing antimicrobial substances to prevent the growth of antibiotic-resistant bacteria and their biofilms. Here, we developed a cotton fabric coated with reduced graphene oxide (rGO) and copper nanoparticles (Cu NPs), which possessed hydrophobic, antimicrobial, and anti-biofilm properties. Once the graphene oxide was dip-coated on a cellulose cotton fabric, Cu NPs were synthesized using a chemical reduction method to fabricate an rGO/Cu fabric, which was analyzed through FE-SEM, EDS, and ICP-MS. The results of our colony-forming unit assays indicated that the rGO/Cu fabric possessed high antibacterial and anti-biofilm properties against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Corynebacterium xerosis, and Micrococcus luteus. Particularly, the fabric could inhibit the growth of E. coli, C. xerosis, and M. luteus with a 99% efficiency. Furthermore, our findings confirmed that the same concentrations of rGO/Cu had no cytotoxic effects against CCD-986Sk and Human Dermal Fibroblast (HDF), human skin cells, and NIH/3T3, a mouse skin cell. The developed rGO/Cu fabric thus exhibited promising applicability as a cotton material that can maintain hygienic conditions by preventing the propagation of various bacteria and sufficiently suppressing biofilm formation while also being harmless to the human body.

Do Curdlan Hydrogels Improved with Bioactive Compounds from Hop Exhibit Beneficial Properties for Skin Wound Healing?

Chronic wounds, among others, are mainly characterized by prolonged inflammation associated with the overproduction of reactive oxygen species and pro-inflammatory cytokines by immune cells. As a consequence, this phenomenon hinders or even precludes the regeneration process. It is known that biomaterials composed of biopolymers can significantly promote the process of wound healing and regeneration. The aim of this study was to establish whether curdlan-based biomaterials modified with hop compounds can be considered as promising candidates for the promotion of skin wound healing. The resultant biomaterials were subjected to an evaluation of their structural, physicochemical, and biological in vitro and in vivo properties. The conducted physicochemical analyses confirmed the incorporation of bioactive compounds (crude extract or xanthohumol) into the curdlan matrix. It was found that the curdlan-based biomaterials improved with low concentrations of hop compounds possessing satisfactory hydrophilicity, wettability, porosity, and absorption capacities. In vitro, tests showed that these biomaterials were non-cytotoxic, did not inhibit the proliferation of skin fibroblasts, and had the ability to inhibit the production of pro-inflammatory interleukin-6 by human macrophages stimulated with lipopolysaccharide. Moreover, in vivo studies showed that these biomaterials were biocompatible and could promote the regeneration process after injury (study on Danio rerio larvae model). Thus, it is worth emphasizing that this is the first paper demonstrating that a biomaterial based on a natural biopolymer (curdlan) improved with hop compounds may have biomedical potential, especially in the context of skin wound healing and regeneration.

Gelatin-Gallic Acid Microcomplexes Release GO/Cu Nanomaterials to Eradicate Antibiotic-Resistant Microbes and Their Biofilm

Wound-infecting bacteria are typically Pseudomonas aeruginosa and Staphylococcus epidermidis, both of which form biofilms and become resistant to antibiotics. To solve this problem, copper nanoparticles (Cu) on graphene oxide (GO) nanosheets were used as antibacterial materials. Since the excessive use of antibacterial substances is fatal to normal tissues, GO/Cu was encapsulated with a gelatin complex to lower the cytotoxicity. Among the catechol-based substances, gallic acid (GA), which has anti-inflammatory and antibacterial properties, was used in this study to impart stability to the gelatin complex. Gelatin (GE) and gallic acid (GA) were combined by a crosslinking method using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) as a crosslinker, and the crosslinking was confirmed by Fourier transform infrared (FT-IR), ¹H NMR, and the fluorescence property of GA. The GO/Cu@GE-GA microcomplexes exhibited more antibacterial effect against Gram-positive bacteria (S. epidermidis) and Gram-negative bacteria (P. aeruginosa) than when GO/Cu alone was used, and the antibiofilm effect was also confirmed. The cytotoxicity evaluation for human skin cells (human dermal fibroblast (HDF)) at the same concentration showed that it had low cytotoxicity and biocompatibility. This study shows the potential of antimicrobial gelatin microcomplex in prohibiting infectious bacteria and their biofilms and controlling the release of antimicrobial substances.

Electrospun Membrane Surface Modification by Sonocoating with HA and ZnO:Ag Nanoparticles—Characterization and Evaluation of Osteoblasts and Bacterial Cell Behavior In Vitro

Guided tissue regeneration and guided bone regeneration membranes are some of the most common products used for bone regeneration in periodontal dentistry. The main disadvantage of commercially available membranes is their lack of bone cell stimulation and easy bacterial colonization. The aim of this work was to design and fabricate a new membrane construct composed of electrospun poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) fibers sonocoated with layers of nanoparticles with specific properties, i.e., hydroxyapatite and bimetallic nanocomposite of zinc oxide–silver. Thus, within this study, four different variants of biomaterials were evaluated, namely: poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) biomaterial, poly(D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite biomaterial, poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano zinc oxide–silver biomaterial, and poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver biomaterial. First, it was demonstrated that the wettability of biomaterials—a prerequisite property important for ensuring desired biological response—was highly increased after the sonocoating process. Moreover, it was indicated that biomaterials composed of poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) with or without a nano hydroxyapatite layer allowed proper osteoblast growth and proliferation, but did not have antibacterial properties. Addition of a nano zinc oxide–silver layer to the biomaterial inhibited growth of bacterial cells around the membrane, but at the same time induced very high cytotoxicity towards osteoblasts. Most importantly, enrichment of this biomaterial with a supplementary underlayer of nano hydroxyapatite allowed for the preservation of antibacterial properties and also a decrease in the cytotoxicity towards bone cells, associated with the presence of a nano zinc oxide–silver layer. Thus, the final structure of the composite poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver seems to be a promising construct for tissue engineering products, especially guided tissue regeneration/guided bone regeneration membranes. Nevertheless, additional research is needed in order to improve the developed construct, which will simultaneously protect the biomaterial from bacterial colonization and enhance the bone regeneration properties.

Biomimetic biphasic curdlan-based scaffold for osteochondral tissue engineering applications - Characterization and preliminary evaluation of mesenchymal stem cell response in vitro

Osteochondral defects remain a huge problem in medicine today. Biomimetic bi- or multi-phasic scaffolds constitute a very promising alternative to osteochondral autografts and allografts. In this study, a new curdlan-based scaffold was designed for osteochondral tissue engineering applications. To achieve biomimetic properties, it was enriched with a protein component - whey protein isolate as well as a ceramic ingredient - hydroxyapatite granules. The scaffold was fabricated via a simple and cost-efficient method, which represents a significant advantage. Importantly, this technique allowed generation of a scaffold with two distinct, but integrated phases. Scanning electron microcopy and optical profilometry observations demonstrated that phases of biomaterial possessed different structural properties. The top layer of the biomaterial (mimicking the cartilage) was smoother than the bottom one (mimicking the subchondral bone), which is beneficial from a biological point of view because unlike bone, cartilage is a smooth tissue. Moreover, mechanical testing showed that the top layer of the biomaterial had mechanical properties close to those of natural cartilage. Although the mechanical properties of the bottom layer of scaffold were lower than those of the subchondral bone, it was still higher than in many analogous systems. Most importantly, cell culture experiments indicated that the biomaterial possessed high cytocompatibility towards adipose tissue-derived mesenchymal stem cells and bone marrow-derived mesenchymal stem cells in vitro. Both phases of the scaffold enhanced cell adhesion, proliferation, and chondrogenic differentiation of stem cells (revealing its chondroinductive properties in vitro) as well as osteogenic differentiation of these cells (revealing its osteoinductive properties in vitro). Given all features of the novel curdlan-based scaffold, it is worth noting that it may be considered as promising candidate for osteochondral tissue engineering applications.

Biosynthesis and applications of curdlan

Curdlan is widely applied in the food and pharmaceutical industries. This review focuses on the biosynthetic pathways, regulatory mechanisms and metabolic engineering strategies for curdlan production. Firstly, curdlan biosynthesis is discussed. Furthermore, various strategies to increase curdlan production are summarized from four aspects, including the overexpression of genes for curdlan biosynthesis, weakening/knockdown of genes from competing pathways, increasing the supply of curdlan precursors, and optimization of fermentation conditions. Moreover, the emerging and advanced applications of curdlan are introduced. Finally, the challenges that are frequently encountered during curdlan biosynthesis are noted with a discussion of directions for curdlan production.

Copper Ions Ameliorated Thermal Burn-Induced Damage in ex vivo Human Skin Organ Culture

INTRODUCTION

The zone of stasis is formed around the coagulation zone following skin burning and is characterized by its unique potential for salvation. The cells in this zone may die or survive depending on the severity of the burn and therefore are target for the local treatments of burns. Their low survival rate is consistent with decreased tissue perfusion, hypotension, infection, and/or edema, resulting in a significant increase in the wound size following burning. Copper is an essential trace mineral needed for the normal function of almost all body tissues, including the skin.

OBJECTIVE

The aim of the work was to study the effect copper ions have on skin burn pathophysiology.

METHODS

Skin obtained from healthy patients undergoing abdominoplasty surgery was cut into 8 × 8 mm squares, and round 0.8-mm diameter burn wounds were inflicted on the skin explants. The burned and control intact skin samples were cultured up to 27 days after wounding. Immediately following injury and then again every 48 h, saline only or containing 0.02 or 1 µM copper ions was added onto the skin explant burn wounds.

RESULTS

We found that exposing the wounded sites immediately after burn infliction to 0.02 or 1 µM copper ions reduced the deterioration of the zone of stasis and the increase in wound size. The presence of the copper ions prevented the dramatic increase of pro-inflammatory cytokines (interleukin (IL)-6 and IL-8) and transforming growth factor beta-1 that followed skin burning. We also detected re-epithelialization of the skin tissue and a greater amount of collagen fibers upon copper treatment.

CONCLUSION

The deterioration of the zone of stasis and the increase in wound size following burning may be prevented or reduced by using copper ion-based therapeutic interventions.

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.

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.