Development of next-generation antimicrobial hydrogel dressing to combat burn wound infection

Multidrug-Resistant Organisms: The Silent Plight of Burn Patients

The global increasing spread of multidrug-resistant organisms (MDROs) is threatening the control of various infections in vulnerable populations and patient groups. One of the most affected groups is patients with burns, who are prone to hyperinfection as they suffer from a hypermetabolic state and weaken immune barriers. Those patients also share the infection risk of patients hospitalized for a long time, including ventilator-associated pneumonia and urinary tract infections. While some preventative and therapeutic management styles are still controversial, we discuss consensuses here. In this review, we aim to present the current knowledge on multidrug resistance with a special focus on patients with burns, discuss various causative organisms and their treatment options, and highlight the importance of antibiotic stewardship and teamwork in responding to an outbreak of MDROs.

Dual-Delivery Temperature-Sensitive Hydrogel with Antimicrobial and Anti-Inflammatory Brevilin A and Nitric Oxide for Wound Healing in Bacterial Infection

Bacterial infections impede the wound healing process and can trigger local or systemic inflammatory responses. Therefore, there is an urgent need to develop a dressing with antimicrobial and anti-inflammatory properties to promote the healing of infected wounds. In this study, BA/COs/NO-PL/AL hydrogels were obtained by adding brevilin A (BA) camellia oil (CO) submicron emulsion and nitric oxide (NO) to hydrogels consisting of sodium alginate (AL) and Pluronic F127 (PL). The hydrogels were characterized through dynamic viscosity analysis, differential scanning calorimetry, and rheology. They were evaluated through anti-inflammatory, antimicrobial, and wound healing property analyses. The results showed that BA/COs/NO-PL/AL hydrogels were thermo-responsive and had good ex vivo and in vivo anti-inflammatory activity, and they also exhibited strong antimicrobial activity against methicillin-resistant Staphylococcus aureus Pseudomonas aeruginosa (MRPA) and methicillin-resistant Staphylococcus aureus (MRSA). They were able to effectively promote healing of the infected wound model and reduce inflammation and bacterial burden. H&E and Masson's staining showed that BA/COs/NO-PL/AL hydrogels promoted normal epithelial formation and collagen deposition. In conclusion, BA/COs/NO-PL/AL hydrogels are promising candidates for promoting the healing of infected wounds.

Deep Eutectic Solvent Eutectogels for Delivery of Broad-Spectrum Antimicrobials

Gel-based wound dressings have gained popularity within the healthcare industry for the prevention and treatment of bacterial and fungal infections. Gels based on deep eutectic solvents (DESs), known as eutectogels, provide a promising alternative to hydrogels as they are non-volatile and highly tunable and can solubilize therapeutic agents, including those insoluble in hydrogels. A choline chloride:glycerol-cellulose eutectogel was loaded with numerous antimicrobial agents including silver nanoparticles, black phosphorus nanoflakes, and commercially available pharmaceuticals (octenidine dihydrochloride, tetracycline hydrochloride, and fluconazole). The eutectogels caused >97% growth reduction in Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria and the fungal species Candida albicans.

Chiral nanomaterials in tissue engineering

Addressing significant medical challenges arising from tissue damage and organ failure, the field of tissue engineering has evolved to provide revolutionary approaches for regenerating functional tissues and organs. This involves employing various techniques, including the development and application of novel nanomaterials. Among them, chiral nanomaterials comprising non-superimposable nanostructures with their mirror images have recently emerged as innovative biomaterial candidates to guide tissue regeneration due to their unique characteristics. Chiral nanomaterials including chiral fibre supramolecular hydrogels, polymer-based chiral materials, self-assembling peptides, chiral-patterned surfaces, and the recently developed intrinsically chiroptical nanoparticles have demonstrated remarkable ability to regulate biological processes through routes such as enantioselective catalysis and enhanced antibacterial activity. Despite several recent reviews on chiral nanomaterials, limited attention has been given to the specific potential of these materials in facilitating tissue regeneration processes. Thus, this timely review aims to fill this gap by exploring the fundamental characteristics of chiral nanomaterials, including their chiroptical activities and analytical techniques. Also, the recent advancements in incorporating these materials in tissue engineering applications are highlighted. The review concludes by critically discussing the outlook of utilizing chiral nanomaterials in guiding future strategies for tissue engineering design.

Injectable hydrogel based on silk fibroin/carboxymethyl cellulose/agarose containing polydopamine functionalized graphene oxide with conductivity, hemostasis, antibacterial, and anti-oxidant properties for full-thickness burn healing

Overcoming bacterial infections and promoting wound healing are significant challenges in clinical practice and fundamental research. This study developed a series of enzymatic crosslinking injectable hydrogels based on silk fibroin (SF), carboxymethyl cellulose (CMC), and agarose, with the addition of polydopamine functionalized graphene oxide (GO@PDA) to endow the hydrogel with suitable conductivity and antimicrobial activity. The hydrogels exhibited suitable gelation time, stable mechanical and rheological properties, high water absorbency, and hemostatic properties. Biocompatibility was also confirmed through various assays. After loading the antibiotic vancomycin hydrochloride, the hydrogels showed sustained release and good antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The fast gelation time and desirable tissue-covering ability of the hydrogels allowed for a good hemostatic effect in a rat liver trauma model. In a rat full-thickness burn wound model, the hydrogels exhibited an excellent treatment effect, leading to significantly enhanced wound closure, collagen deposition, and granulation tissue formation, as well as neovascularization and anti-inflammatory effects. In conclusion, the antibacterial electroactive injectable hydrogel dressing, with its multifunctional properties, significantly promoted the in vivo wound healing process, making it an excellent candidate for full-thickness skin wound healing.

Evolutionary and in silico guided development of novel peptide analogues for antibacterial activity against ESKAPE pathogens

According to WHO, to combat the resistant strains, new effective anti-microbial agents are needed on an urgent basis and global researchers should focus their efforts and discovery programs on developing them against antibiotic-resistant pathogens or priority pathogens like ESKAPE. In this context, Cationic antimicrobial peptides (AMPs) are being explored extensively as promising next-generation antimicrobials due to their broad range, fast kinetics and multifunctional role. Despite recent advances, it is still a daunting challenge to identify and design a potent AMP with no cytotoxicity, but with broad specific antimicrobial activity, stability and efficacy under in vivo conditions in a cost-effective and robust manner. In this work, as a proof of concept, we designed novel potent AMPs using artificial intelligence based in silico programs. Shortlisted peptide sequences were synthesized using the fmoc chemistry approach, assessed their antimicrobial activity, cell selectivity, mode of action and in vivo efficacy using a series of experiments. The synthesized peptide analogues demonstrated their antimicrobial activity (MIC in the range of 2.5-80 μM) against bacteria. The identified potential lead molecules showed antibacterial activity in physiological conditions with no signs of cytotoxicity. We further tested the antimicrobial activity of peptide analogues for treating wounds infected with Pseudomonas aeruginosa in the mice burn wound model. In drug-development programs, the identification of lead antimicrobial agents is always challenging and involves screening a large number of molecules which is time-consuming and expensive. This work demonstrates the utility of artificial intelligence based in silico analysis programs in discovering novel antimicrobial agents in an economical, robust way.

Treatment of experimentally induced partial-thickness burns in rats with different silver-impregnated dressings

PURPOSE

To evaluate the morphometric, macroscopic and microscopic aspects of experimentally induced partial-thickness burns in rats treated with different silver-based dressings.

METHODS

Wistar rats were used, divided into six treatments: saline (NaCl 0.9%); silver sulfadiazine 1%; Silvercel; Mepilex Ag; Aquacel Ag and Acticoat. The animals were monitored daily and euthanized at 7, 14 and 30 days after injury induction (DAI).

RESULTS

At 7 DAI, necrosis/crust was greater in control, silver sulfadiazine and Mepilex Ag treatments, granulation tissue was induced by Aquacel Ag, polymorphonuclear infiltrate (PMN) infiltration was intensified by Mepilex Ag; mononuclear infiltrate (MN) infiltration and angiogenesis were increased by Silvercel. At 14 DAI, hemorrhage was decreased by Silvercel and Mepilex Ag, PMN infiltration increased by Acticoat. At 30 DAI, angiogenesis was greater in the Acticoat treatment and fibroblasts were increased by Acticoat and Mepilex Ag. Collagen was induced at 14 DAI by silver sulfadiazine and Aquacel Ag and, at 30 DAI, by silver sulfadiazine and Silvercel treatments.

CONCLUSIONS

Silvercel and Acticoat presented better results than the other products. However, all the dressings were better than the control at some point during the process, and may contribute to the healing of partial thickness burns. Silvercel and Aquacel Ag treatments induced better cosmetic outcomes regarding wound closure and scarring.

Bacteria-Activated Dual pH- and Temperature-Responsive Hydrogel for Targeted Elimination of Infection and Improved Wound Healing

Antibacterial treatment that provides on-demand release of therapeutics that can kill a broad spectrum of pathogens while maintaining long-term efficacy and without developing resistance or causing side effects is urgently required in clinical practice. Here, we demonstrate the development of a multistimuli-responsive hydrogel, prepared by cross-linking N-isopropylacrylamide with acrylic acid and loaded with ultrasmall silver nanoparticles (AgNPs), offering the on-demand release of Ag⁺ ions triggered by changes in the wound microenvironment. We demonstrate that this dual-responsive hydrogel is highly sensitive to a typical wound pH and temperature change, evidenced by the restricted release of Ag⁺ ions at acidic pH (<5.5) while significantly promoting the release in alkaline pH (>7.4) (>90% release). The pH-dependent release and antibacterial effect show minimal killing at pH 4 or 5.5 but dramatically activated at pH 7.4 and 10, eliminating >95% of the pathogens. The in vivo antibacterial efficacy and safety showed a high potency to clear Staphylococcus aureus wound infection while significantly accelerating the wound healing rate. This multifunctional hydrogel presents a promising bacteria-responsive delivery platform that serves as an on-demand carrier to not only reduce side effects but also significantly boost the antibacterial efficiency based on physiological needs. It offers great potential to improve the way wound infections are treated with direct clinical implications, providing a single platform for long-lasting application in wound management.

Evaluating polymeric biomaterials to improve next generation wound dressing design

Wound healing is a dynamic series of interconnected events with the ultimate goal of promoting neotissue formation and restoration of anatomical function. Yet, the complexity of wound healing can often result in development of complex, chronic wounds, which currently results in a significant strain and burden to our healthcare system. The advancement of new and effective wound care therapies remains a critical issue, with the current therapeutic modalities often remaining inadequate. Notably, the field of tissue engineering has grown significantly in the last several years, in part, due to the diverse properties and applications of polymeric biomaterials. The interdisciplinary cohesion of the chemical, biological, physical, and material sciences is pertinent to advancing our current understanding of biomaterials and generating new wound care modalities. However, there is still room for closing the gap between the clinical and material science realms in order to more effectively develop novel wound care therapies that aid in the treatment of complex wounds. Thus, in this review, we discuss key material science principles in the context of polymeric biomaterials, provide a clinical breadth to discuss how these properties affect wound dressing design, and the role of polymeric biomaterials in the innovation and design of the next generation of wound dressings.

Polyurethane based hybrid ciprofloxacin-releasing wound dressings designed for skin engineering purpose

PURPOSE

Even in the 21st century, chronic wounds still pose a major challenge due to potentially inappropriate treatment options, so the latest wound dressings are hybrid systems that enable clinical management, such as a hybrid of hydrogels, antibiotics and polymers. These wound dressings are mainly used for chronic and complex wounds, which can easily be infected by bacteria.

MATERIALS AND METHODS

Six Composite Porous Matrices (CPMs) based on polyurethane (PUR) in alliance with polylactide (PLAs) and poly(vinyl alcohol) (PVA) were prepared and analyzed using optical microscopy. Three different types of hydrogels and their Ciprofloxacin (Cipro) modified variants' ratios were prepared and analyzed using FTIR, SEM and EDX techniques. Six Hybrid Cipro-Releasing Hydrogel Wound Dressings (H-CRWDs) were also prepared and underwent short-term degradation, Cipro release, microbiology and cell viability measurements.

RESULTS

Average porosity of CPMs was in the range of 69-81%. The pore size of the obtained CPMs was optimal for skin regeneration. Short-term degradation studies revealed degradability in physiological conditions regardless of sample type. A meaningful release was also observed even in short time (21.76 ​± ​0.64 ​μg/mL after 15 ​min). Microbiological tests showed visible inhibition zones. Cell viability tests proved that the obtained H-CRWDs were biocompatible (over 85% of cells).

CONCLUSIONS

A promising hybrid wound dressing was labeled. Simple and cost-effective methods were used to obtain microbiologically active and biocompatible dressings. The results were of importance for the design and development of acceptable solutions in the management of chronic wounds of high potential for infection.

Hydrogels in Burn Wound Management-A Review

Inert hydrogels are of a great importance in burn first aid. Hydrogel dressings may be an alternative to cooling burn wounds with streaming water, especially in cases of mass casualty events, lack of clean water, hypothermia, or large extent of burns. Hydrogels that contain mostly water evacuate the heat cumulating in the skin by evaporation. They not only cool the burn wound, but also reduce pain and protect the wound area from contamination and further injuries. Hydrogels are ideally used during the first hours after injury, but as they do not have antimicrobial properties per se, they might not prevent wound infection. The hydrogel matrix enables incorporating active substances into the dressing. The active forms may contain ammonium salts, nanocrystal silver, zinc, growth factor, cytokines, or cells, as well as natural agents, such as honey or herbs. Active dressings may have antimicrobial activity or stimulate wound healing. Numerous experiments on animal models proved their safety and efficiency. Hydrogels are a new dressing type that are still in development.

In Vitro and In Vivo Studies on the Antibacterial Activity and Safety of a New Antimicrobial Peptide Dermaseptin-AC

Antimicrobial resistance has been an increasing public health threat in recent years. Antimicrobial peptides are considered as potential drugs against drug-resistant bacteria because they are mainly broad-spectrum and are unlikely to cause resistance. In this study, a novel peptide was obtained from the skin secretion of Agalychnis callidryas using the “shotgun” cloning method. The amino acid sequence, molecular weight, and secondary structure of Dermaseptin-AC were determined. The in vitro antimicrobial activity, hemolysis, and cytotoxicity of Dermaseptin-AC were evaluated. MICs and minimum bactericidal concentrations (MBCs) of Dermaseptin-AC against seven different bacterial strains ranged between 2 ∼ 4 μM and 2 ∼ 8 μM. The HC₅₀ (50% maximum hemolysis concentration) of Dermaseptin-AC against horse erythrocytes was 76.55 μM. The in vivo anti-MRSA effect was tested on immune-suppressed MRSA pneumonia in mice. Dermaseptin-AC showed anti-MRSA effects similar to the same dose of vancomycin (10 mg/kg body weight). Short-term (7 days of intraperitoneal injection, 10 mg/kg body weight) in vivo safety evaluation of Dermaseptin-AC was tested on mice. The survival rate during the 7-day injection was 80%. Dermaseptin-AC showed no obvious effect on the liver, heart, spleen, kidney, and blood, but did induce slight pulmonary congestion. The skin safety of Dermaseptin-AC was evaluated on wounds on the back skin of a rat, and no irritation was observed.

IMPORTANCE In this study, we discovered a new antimicrobial peptide, Dermaseptin-AC, and studied its in vitro and in vivo antimicrobial activity. These studies provide some data for finding new antimicrobial peptides for overcoming antimicrobial resistance. Dermaseptin-AC showed strong broad-spectrum antibacterial activity and relatively low hemolysis, and was more cytotoxic to cancer cells than to normal cells. Dermaseptin-AC was active in vivo, and its anti-MRSA effect was similar to that of vancomycin when administered by intraperitoneal injection. Safety studies found that continuous injection of Dermaseptin-AC may cause mild pulmonary congestion, while there was no obvious irritation when it was applied to skin wounds. Chronic wounds are often accompanied by high bacterial burdens and, at the same time, antimicrobial resistance is more likely to occur during repeated infections and treatments. Therefore, developing Dermaseptin-AC to treat chronic wound infection may be an attractive choice.

Antimicrobial efficacy of Egyptian Eremina desertorum and Helix aspersa snail mucus with a novel approach to their anti-inflammatory and wound healing potencies

Snail mucus is composed of bioactive compounds thought to have different biological properties for the treatment of some skin problems. Although Helix aspersa mucus is used in several cosmetic products, a detailed characterization of Eremina desertorum mucus composition and its biological activities is still missing. Mucus extracts (MEs) from H. aspersa and E. desertorum were prepared and tested for their antimicrobial and anti-inflammatory activities with their potencies in wound healing. Also, chemical characterization was performed by GC-MS analysis. Results showed that ME of E. desertorum gave higher inhibitory activity against resistant strains related to burn wound infections compared to ME of H. aspersa. Additionally, it revealed a significant anti-inflammatory activity. Moreover, we found that ME of E. desertorum lacked cytotoxicity and was able to significantly induce cell proliferation and migration through up-regulation of TGF-β1 and VEGF gene expression. Our results suggested that MEs of E. desertorum have higher biological effects than H. aspersa, which are attributable to antimicrobial, anti-inflammatory activities, cell proliferation and pave the way for further investigating its potential effect as a human therapeutic agent.

A Sequential Therapeutic Hydrogel With Injectability and Antibacterial Activity for Deep Burn Wounds' Cleaning and Healing

As a severe clinical challenge, escharotomy and infection are always the core concerns of deep burn injuries. However, a usual dressing without multifunctionality leads to intractable treatment on deep burn wounds. Herein, we fabricated a sequential therapeutic hydrogel to solve this problem. Cross-linked by modified polyvinyl alcohol (PVA-SH/ε-PL) and benzaldehyde-terminated F127 triblock copolymers (PF127-CHO), the hydrogel demonstrated excellent mechanical properties, injectability, tissue adhesiveness, antibacterial activity, biocompatibility, and satisfactory wound cleaning through both in vitro and in vivo assays. Additionally, based on the conception of “sequential therapy,” we proposed for the first time to load bromelain and EGF into the same hydrogel in stages for wound cleaning and healing. This work provides a strategy to fabricate a promising wound dressing for the treatment of deep burn wounds with injectability and improved patients’ compliance as it simplified the process of treatment due to its “three in one” characteristic (antibacterial activity, wound cleaning, and healing effects); therefore, it has great potential in wound dressing development and clinical application.

Eradication of Mature Bacterial Biofilms with Concurrent Improvement in Chronic Wound Healing Using Silver Nanoparticle Hydrogel Treatment

Biofilm-associated infections are a major cause of impaired wound healing. Despite the broad spectrum of anti-bacterial benefits provided by silver nanoparticles (AgNPs), these materials still cause controversy due to cytotoxicity and a lack of efficacy against mature biofilms. Herein, highly potent ultrasmall AgNPs were combined with a biocompatible hydrogel with integrated synergistic functionalities to facilitate elimination of clinically relevant mature biofilms in-vivo combined with improved wound healing capacity. The delivery platform showed a superior release mechanism, reflected by high biocompatibility, hemocompatibility, and extended antibacterial efficacy. In vivo studies using the S. aureus wound biofilm model showed that the AgNP hydrogel (200 µg/g) was highly effective in eliminating biofilm infection and promoting wound repair compared to the controls, including silver sulfadiazine (Ag SD). Treatment of infected wounds with the AgNP hydrogel resulted in faster wound closure (46% closure compared to 20% for Ag SD) and accelerated wound re-epithelization (60% for AgNP), as well as improved early collagen deposition. The AgNP hydrogel did not show any toxicity to tissue and/or organs. These findings suggest that the developed AgNP hydrogel has the potential to be a safe wound treatment capable of eliminating infection and providing a safe yet effective strategy for the treatment of infected wounds.

Changes of Mineralogical Properties and Biological Activities of Gypsum and Its Calcined Products with Different Phase Structures

Raw gypsum (RG) and calcined gypsum (CG) are widely used in traditional Chinese medicine (TCM). RG is usually taken orally to resolve heat and diminish inflammation, while CG is only used externally to treat ulcerations and empyrosis. Calcination at different temperatures, three phase CG structures, namely, bassanite, anhydrite III, and anhydrite II, may be generated. We herein investigated the relationship between the phase structure and the efficacy of CG and the optimum phase structure for CG. RG has a compact structure, small pore size, weak anti-inflammatory effect, but no antibacterial effect, and has almost no effect on the repair of scalds. CG150 (bassanite) has a loose texture, large pore size and specific surface area, and certain antibacterial and anti-inflammatory effects, but it has a poor repair effect on scalds. CG750 (anhydrite II) has a compact structure, small pore size and specific surface area, and low antibacterial and anti-inflammatory effects, but it has a certain repair effect on scalds. Only CG350 (anhydrite III) has good performance in texture, pore size, specific surface area, antibacterial, anti-inflammatory, and scald repair. Our research has proved that the mineral properties and biological activities of CG are different due to different phase structures. CG350, namely, anhydrite III, is considered by our research to be the optimal phase structure as CG.