Antimicrobial and Wound Treatment Aspects of Micro‐ and Nanoformulations of Carboxymethyl,Dialdehyde, and TEMPO‐Oxidized Derivatives of Cellulose: Recent Advances

The remedy for infected chronic wounds such as diabetic foot ulcers is more complicated particularly in the case of patients with an inefficient immune system. Also, fighting against microbial infections in the wound site by available antibiotics may not be effective because of emerging antibiotic resistance properties among pathogenic bacteria and fungi. Recently, applications of micro‐ and nanoformulations of biomaterials have demonstrated improved therapeutic abilities for wound dressings. In this way, carboxymethyl, dialdehyde, and 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐oxidized celluloses are common biomaterials having outstanding physicochemical and therapeutic properties compared to unmodified cellulose. Therefore, in this review, recent progress in the field of wound healing and antimicrobial activities of these derivatives are presented and discussed.     

Topical propolis improves wound healing in patients with diabetic foot ulcer: a randomized controlled trial

In this randomized controlled trial, diabetic patients with foot ulcers (Wagner grades 1 and 2) were randomly assigned to conventional therapies for diabetic foot ulcer plus topical propolis ointment (5%; twice daily) or conventional therapies alone. The process of ulcer healing was observed during 4 weeks and compared between the two groups regarding the size, erythema, exudates, white blood cell (WBC) count and erythrocyte sedimentation rate (ESR). The process of ulcer size reduction during the four-week period of study was significantly different between the groups. However, this difference was not significant between the third and fourth weeks. There was no significant difference between two groups regarding erythema and exudate reduction as well as WBC count and ESR. Administration of topical propolis ointment in addition to the conventional treatments of diabetic foot ulcer could reduce the size of ulcers with Wagner grades 1 and 2.     

Antimicrobial and wound healing activities of electrospun nanofibers based on functionalized carbohydrates and proteins

The anti-adhesion, anti-growth and the anti-penetration of bacteria, specifically multidrug-resistant bacteria, should be taken into consideration when designing promising wound dressings for infected wounds such as diabetic foot ulcers. Wound dressings composed of natural polymeric nanofibers such as functionalized cellulose, chitosan, alginate, hyaluronic acid, dextrin and cyclodextrin with appropriate antimicrobial and skin reconstruction properties are suitable alternatives that can accelerate wound healing and remove microbial infections. For instance, to improve the release profile of antibacterial agents such as metal nanoparticles and antibiotics, water-soluble polymers like polyethylene oxide and polyvinylpyrrolidone may be incorporated into polymeric nanofiber scaffolds. This review, therefore, addresses the current status and future challenges of antibacterial activities of nanofiber scaffolds composed of some of the natural occurring polymers.

     

Natural okra-based hydrogel for chronic diabetic wound healing

As a representative of chronic wounds, the long-term high levels of oxidative stress and blood sugar in chronic diabetic wounds lead to serious complications, making them the biggest challenge in the research on wound healing. Many edible natural biomaterials rich in terpenes, phenols, and flavonoids can act as efficient antioxidants. In this study, okra extract was selected as the main component of a wound dressing. The okra extracts obtained via different methods comprehensively maintained the bioactivity of multiple molecules. The robust antioxidant properties of okra significantly reduced intracellular reactive oxygen species production, thereby accelerating the wound healing process. The results showed that okra extracts and their hydrogel dressings increased cell migration, angiogenesis, and re-epithelization of the chronic wound area, considerably promoting wound remodeling in diabetic rats. Therefore, okra-based hydrogels are promising candidates for skin regeneration and wider tissue engineering applications.     

Keratin Scaffolds Containing Casomorphin Stimulate Macrophage Infiltration and Accelerate Full-Thickness Cutaneous Wound Healing in Diabetic Mice

Impaired wound healing is a major medical challenge, especially in diabetics. Over the centuries, the main goal of tissue engineering and regenerative medicine has been to invent biomaterials that accelerate the wound healing process. In this context, keratin-derived biomaterial is a promising candidate due to its biocompatibility and biodegradability. In this study, we evaluated an insoluble fraction of keratin containing casomorphin as a wound dressing in a full-thickness surgical skin wound model in mice (n = 20) with iatrogenically induced diabetes. Casomorphin, an opioid peptide with analgesic properties, was incorporated into keratin and shown to be slowly released from the dressing. An in vitro study showed that keratin-casomorphin dressing is biocompatible, non-toxic, and supports cell growth. In vivo experiments demonstrated that keratin-casomorphin dressing significantly (p < 0.05) accelerates the whole process of skin wound healing to the its final stage. Wounds covered with keratin-casomorphin dressing underwent reepithelization faster, ending up with a thicker epidermis than control wounds, as confirmed by histopathological and immunohistochemical examinations. This investigated dressing stimulated macrophages infiltration, which favors tissue remodeling and regeneration, unlike in the control wounds in which neutrophils predominated. Additionally, in dressed wounds, the number of microhemorrhages was significantly decreased (p < 0.05) as compared with control wounds. The dressing was naturally incorporated into regenerating tissue during the wound healing process. Applied keratin dressing favored reconstruction of more regular skin structure and assured better cosmetic outcome in terms of scar formation and appearance. Our results have shown that insoluble keratin wound dressing containing casomorphin supports skin wound healing in diabetic mice.     

Polymer-based Biomaterials as Dressings for Chronic Stagnating Wounds

Chronic wounds, such as venous, pressure, and diabetic ulcers, are difficult to heal and represent a rising social and economical problem. Compared to acute wounds, non-healing wounds contain elevated levels of neutrophil elastase, pro-inflammatory cytokines (IL-1β, IL-6, IL-8), and matrix metalloproteases (MMP-2, MMP-9, MMP-13) as well as free radicals. Their overproduction perpetuates the inflammatory phase resulting in severe tissue damage and degradation of growth factors. Consequently, wound closure is prevented and the wound remains non-healing for month or even years. The increasing numbers of patients suffering from wounds that fail to heal are a significant challenge for health care professionals. Wound dressings play an important role in the entire management of these wounds. New materials and treatment strategies are needed to improve wound care. Recent advances in the field of biomaterials and their medical applications indicate the significance and potential of various natural polymers in the development of novel classes of wound dressings. Native polymers are an ideal source for bio-active wound dressings because of their availability and biocompatibility. Hence, several studies have been conducted to explore the influence of wound dressings consisting of collagen, oxidized regenerated cellulose, bacterial cellulose, chitosan, or alginate on the destructive milieu in chronic wounds.     

Skin and wound delivery systems for antimicrobial peptides

Non-healing wounds cause hundreds of thousands of deaths every year, and result in large costs for society. A key reason for this is the prevalence of challenging bacterial infections, which may dramatically hinder wound healing. With resistance development among bacteria against antibiotics, this situation has deteriorated during the last couple of decades, pointing to an urgent need for new wound treatments. In particular, this applies to wound dressings able to combat bacterial infection locally in wounds and impaired skin, including those formed by bacteria resistant to conventional antibiotics. Within this context, antimicrobial peptides (AMPs) are currently receiving intense interest. AMPs are amphiphilic peptides, frequently net positively charged, and with a sizable fraction of hydrophobic amino acids. Through destabilization of bacterial membranes, neutralization of inflammatory lipopolysaccharides, and other mechanisms, AMPs can be designed for potent antimicrobial effects, also against antibiotics-resistant strains, and to provide immunomodulatory effects while simultaneously displaying low toxicity. While considerable attention has been placed on AMP optimization and clarification of their mode(s)-of-action, much less attention has been paid on efficient AMP delivery. Considering that AMPs are large molecules, net positively charged, amphiphilic, and susceptible to infection-mediated proteolytic degradation, efficient in vivo delivery of such peptides is, however, challenging and delivery systems needed for the realization of AMP-based therapeutics. In the present work, recent developments regarding AMP delivery systems for treatment of wounds and skin infections are discussed, with the aim to link results from physicochemical studies on, e.g., peptide loading/release, membrane interactions, and self-assembly, with those on the biological functional performance of AMP delivery systems in terms of antimicrobial effects, cell toxicity, inflammation, and wound healing.     

Dose–Response Relationship of Photobiomodulation Therapy on Matrix Metalloproteinase in Healing Dynamics of Diabetic Neuropathic Ulcers—An in vivo Study

Individuals with diabetic foot ulcers have overlapped the inflammatory, proliferative and remodeling phase, making the tissue vulnerable to delayed healing responses. We aimed to establish the dose–response relationship of photobiomodulation therapy of different doses and matrix metalloproteinases in the healing dynamics of diabetic neuropathic ulcers. Diabetes was induced in 126 Albino Wistar rats, and neuropathy was induced to the hind paw by a sciatic nerve injury method. An excisional wound was created on the neuropathy-induced leg. Photobiomodulation therapy of dosages 4, 6, 8, 10, 12 and 15 J cm⁻² and wavelength 655 nm and 808 nm was irradiated. Photobiomodulation therapy of dosages 4, 6 and 8 J cm⁻² showed better wound healing properties with optimized levels of matrix metalloproteinases-1 and 8. We observed a strong dose response in the experimental group treated with 6 and 8 J cm⁻². The findings from the present study conclude that photobiomodulation therapy of dosages 4, 6 and 8 J cm⁻² is suggestive of usefulness in diabetic neuropathic ulcer healing. Markers like matrix metalloproteinases may give a clear direction on response to the therapy. Based on the findings from the present study, we recommend to validate the findings for safety and efficacy in future through human prospective randomized controlled clinical trials.     

Smart biomaterial-based systems for intrinsic stimuli-responsive chronic wound management

Skin chronic wounds are associated with a state of persistent inflammation and often with infection, originating a specific microenvironment characterized by increased temperature, alkaline pH, elevated enzymatic activity, and high levels of reactive oxygen species (ROS). These alterations can be explored as intrinsic triggers in the design of stimuli-responsive biomaterials for the release of bioactive molecules at the wound microenvironment. Stimuli-responsive biomaterials may not only prolong the bioactivity of the therapeutic agents but also synchronize it with the healing stages, tuning the wound treatment. In addition, the high activity of enzymes, such as lysozyme in infected chronic wounds, as well as the shift to a more alkaline pH may be used as biomarkers for early detection of infected and/or non-healing wounds. Overall, although a few shortcomings still need to be addressed before clinical translation, the bioengineered smart formulations highlighted in this review stand out as a new generation of therapies to manage skin chronic wounds.     

Creation of Chitosan-Based Nanocapsule-in-Nanofiber Structures for Hydrophobic/Hydrophilic Drug Co-Delivery and Their Dressing Applications in Diabetic Wounds

Nanofiber meshes (NFMs) loaded with therapeutic agents are very often employed to treat hard-to-heal wounds such as diabetic wounds. However, most of the NFMs have limited capability to load multiple or hydrophilicity distinctive-therapeutic agents. The therapy strategy is therefore significantly hampered. To tackle the innate drawback associated with the drug loading versatility, a chitosan-based nanocapsule-in-nanofiber (NC-in-NF) structural NFM system is developed for simultaneous loading of hydrophobic and hydrophilic drugs. Oleic acid-modified chitosan is first converted into NCs by the developed mini-emulsion interfacial cross-linking procedure, followed by loading a hydrophobic anti-inflammatory agent Curcumin (Cur) into the NCs. Sequentially, the Cur-loaded NCs are successfully introduced into reductant-responsive maleoyl functional chitosan/polyvinyl alcohol NFMs containing a hydrophilic antibiotic Tetracycline hydrochloride. Having a co-loading capability for hydrophilicity distinctive agents, biocompatibility, and a controlled release property, the resulting NFMs have demonstrated the efficacy on promoting wound healing either in normal or diabetic rats.     

Multifunctional fibrous wound dressings for refractory wound healing

Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly.     

Hydrogel adhesives for generalized wound treatment: Design and applications

Wound refers to the place where human body is injured and ruptured. So, wounds in a broad sense include not only skin wounds, but also damages of muscle, corneal, heart, and lung, etc. As “gold standard” of wound closure, suture and staple cause secondary damage to the tissue, and require professional skills and equipment, so noninvasive hydrogel adhesives have been developed as an alternative to close and treat different kinds of wounds. However, the existing reviews mainly discussed the research of hydrogel adhesives for skin wounds, and the focus is mostly on its types and adhesion mechanisms, but a review comprehensively discusses the design and application of hydrogel adhesives on generalized wounds for wound closure and wound healing and the unique needs of various wounds for hydrogel adhesives is still lacking. In this review, the types and adhesion mechanisms of hydrogel adhesives will be briefly described, then the research progress of hydrogel adhesives in wound treatment is reviewed in detail from two aspects: the comprehensive design principles and the unique requirements of different types of wounds. Overall, we expect that this review will provide guidance for the development of hydrogel adhesives as new avenues for generalized wound care and treatment.     

Nanoparticle-based therapeutic approaches for wound healing: a review of the state-of-the-art

Wound healing is a complex physiological procedure that includes diverse stages, comprising hemostasis, inflammation, proliferation, and remodeling to reconstruct the skin and subcutaneous tissue's integrity. As reported, various coexisting diseases (diabetes, vascular diseases, etc.) substantially impact wound healing. Factors like recurring injury, age, or hypertrophic scarring also affect wound healing. The management of wound care depends primarily on the advancement of novel and efficient wound dressing substances, and it persists to be a vivid research area in chronic wound healing. Over the past years, the investigation and advancement of wound dressing biomaterials have registered a new standard level, and superior knowledge based on chronic wound pathogenesis has been achieved. Recently, nanotechnology has presented an excellent method to accelerate acute and chronic wound healing via stimulating appropriate movement through the diverse healing stages. Among various nanomaterials, nanoparticles (NPs) have been spotlighted as an efficient treatment strategy for wound healing due to their ability to act as both a therapeutic and carrier system. Their small size and high surface area to volume ratio enhance the probability of bio-interaction and penetration at the wound area aiding cell–cell interactions, the proliferation of cells, cell signaling, and vascularization. This review endeavored to throw light on different aspects of wounds and the latest advances in nanoparticle-based biomaterials for effective wound healing. Further, challenges and future potentialities have been addressed.     

Skin Wound Healing: Normal Macrophage Function and Macrophage Dysfunction in Diabetic Wounds

Macrophages play a prominent role in wound healing. In the early stages, they promote inflammation and remove pathogens, wound debris, and cells that have apoptosed. Later in the repair process, they dampen inflammation and secrete factors that regulate the proliferation, differentiation, and migration of keratinocytes, fibroblasts, and endothelial cells, leading to neovascularisation and wound closure. The macrophages that coordinate this repair process are complex: they originate from different sources and have distinct phenotypes with diverse functions that act at various times in the repair process. Macrophages in individuals with diabetes are altered, displaying hyperresponsiveness to inflammatory stimulants and increased secretion of pro-inflammatory cytokines. They also have a reduced ability to phagocytose pathogens and efferocytose cells that have undergone apoptosis. This leads to a reduced capacity to remove pathogens and, as efferocytosis is a trigger for their phenotypic switch, it reduces the number of M2 reparative macrophages in the wound. This can lead to diabetic foot ulcers (DFUs) forming and contributes to their increased risk of not healing and becoming infected, and potentially, amputation. Understanding macrophage dysregulation in DFUs and how these cells might be altered, along with the associated inflammation, will ultimately allow for better therapies that might complement current treatment and increase DFU’s healing rates.     

Titanium Nanorods Loaded PCL Meshes with Enhanced Blood Vessel Formation and Cell Migration for Wound Dressing Applications

Proper management of nonhealing wounds is an imperative clinical challenge. For the effective healing of chronic wounds, suitable wound coverage materials with the capability to accelerate cell migration, cell proliferation, angiogenesis, and wound healing are required to protect the healing wound bed. Biodegradable polymeric meshes are utilized as effective wound coverage materials to protect the wounds from the external environment and prevent infections. Among them, electrospun biopolymeric meshes have got much attention due to their extracellular matrix mimicking morphology, ability to support cell adhesion, and cell proliferation. Herein, electrospun nanocomposite meshes based on polycaprolactone (PCL) and titanium dioxide nanorods (TNR) are developed. TNR incorporated PCL meshes are fabricated by electrospinning technique and characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) analysis, and X‐Ray diffraction (XRD) analysis. In vitro cell culture studies, in ovo angiogenesis assay, in vivo implantation study, and in vivo wound healing study are performed. Interestingly, obtained in vitro and in vivo results demonstrated that the presence of TNR in the PCL meshes greatly improved the cell migration, proliferation, angiogenesis, and wound healing. Owing to the above superior properties, they can be used as excellent biomaterials in wound healing and tissue regeneration applications.     

Acidified Nitrite Accelerates Wound Healing in Type 2 Diabetic Male Rats: A Histological and Stereological Evaluation

Impaired skin nitric oxide production contributes to delayed wound healing in type 2 diabetes (T2D). This study aims to determine improved wound healing mechanisms by acidified nitrite (AN) in rats with T2D. Wistar rats were assigned to four subgroups: Untreated control, AN-treated control, untreated diabetes, and AN-treated diabetes. AN was applied daily from day 3 to day 28 after wounding. On days 3, 7, 14, 21, and 28, the wound levels of vascular endothelial growth factor (VEGF) were measured, and histological and stereological evaluations were performed. AN in diabetic rats increased the numerical density of basal cells (1070 ± 15.2 vs. 936.6 ± 37.5/mm³) and epidermal thickness (58.5 ± 3.5 vs. 44.3 ± 3.4 μm) (all p < 0.05); The dermis total volume and numerical density of fibroblasts at days 14, 21, and 28 were also higher (all p < 0.05). The VEGF levels were increased in the treated diabetic wounds at days 7 and 14, as was the total volume of fibrous tissue and hydroxyproline content at days 14 and 21 (all p < 0.05). AN improved diabetic wound healing by accelerating the dermis reconstruction, neovascularization, and collagen deposition.     

Characterization of silver sulfadiazine-loaded solid lipid nanoparticles by thermal analysis

The aim of this study is the solid-state characterization of solid lipid nanoparticles (SLN) based on Compritol^® 888 (C888) and Lutrol^® F68 (F68), loaded with silver sulfadiazine (AgSD), used to develop sponge-like dressings to treat chronic skin ulcers such as decubitis and leg ulcers. Silver compounds like AgSD, in fact, are used to prevent and/or to treat wound colonization that could impair healing, also in the case of antibiotic-resistant bacteria. Thermal analysis, with support from powder X-ray diffractometry and Fourier transform infrared spectroscopy, is used to characterize lipid and drug bulk, unloaded and drug-loaded SLN. In particular, differential scanning calorimetry is used to investigate the degree of crystallinity and the solid-state modification of lipid, two parameters correlated to drug incorporation and drug release rates. The solid-state characterization demonstrates AgSD entrapment in C888 as a core enclosed into F68 shell. AgSD SLN are also stored at different temperatures 25 and 37 °C, respectively, to study the effect of storage conditions, that induce an increase of the lipid crystallinity index correlated to drug release from the lipid matrix.     

Bioinspired Platelet-Anchored Electrospun Meshes for Tight Inflammation Manipulation and Chronic Diabetic Wound Healing

Tight manipulation of the initial leukocytes infiltration and macrophages plasticity toward the M2 phenotype remain a challenge for diabetic wound healing. Inspired by the platelet function and platelet–macrophage interaction, a platelet-anchored polylactic acid-b-polyethylene glycol-b-polylactic acid (PLA-PEG-PLA) electrospun dressing is developed for inflammatory modulation and diabetic wounds healing acceleration. PLA-PEG-PLA electrospun meshes encapsulated with thymosin β4 (Tβ4) and CaCl₂ is fabricated with electrospinning, followed by immersion of electrospun mesh in platelet-rich plasma to firmly anchor the platelets. It is demonstrated that the anchored platelets on electrospun mesh can enhance the initial macrophage recruitment and control the Tβ4 release from electrospun meshes to facilitate the macrophages polarization to the M2 phenotype. The inflammatory regulation promotes the expression of vascular endothelial growth factor and the migration of vascular endothelial cells for angiogenesis, resulting in accelerated diabetic wounds healing. Therefore, this work paved a new way to design platelet-inspired electrospun meshes for inflammation manipulation and diabetic wound healing.     

Effect of the lectin of Bauhinia variegata and its recombinant isoform on surgically induced skin wounds in a murine model

Lectins are a structurally heterogeneous group of highly specific carbohydrate-binding proteins. Due to their great biotechnological potential, lectins are widely used in biomedical research. The purpose of the present study was to evaluate the healing potential of the lectin of Bauhinia variegata (nBVL) and its recombinant isoform (rBVL-1). Following surgical creation of dorsal skin wounds, seven groups of mice were submitted to topical treatment for 12 days with lectin, D-galactose, BSA and saline. The animals were anesthetized and euthanized on POD 2, 7 and 12 in order to evaluate the healing potential of each treatment. The parameters considered included wound size, contraction rate, epithelialization rate and histopathological findings. Wound closure was fastest in animals treated with rBVL-1 (POD 7). nBVL was more effective than the controls. All skin layers were reconstructed and keratin deposition increased. Our findings indicate that the lectin of Bauhinia variegata possesses pro-healing properties and may be employed in the treatment of acute skin wounds.     

Antibacterial,Adhesive, and Conductive Hydrogel for Diabetic Wound Healing

Diabetic mellitus is one of the leading causes of chronic wounds and remains a challenging issue to be resolved. Herein, a hydrogel with conformal tissue adhesivity, skin-like conductivity, robust mechanical characteristics, as well as active antibacterial function is developed. In this hydrogel, silver nanoparticles decorated polypyrrole nanotubes (AgPPy) and cobalt ions (Co²⁺) are introduced into an in situ polymerized poly(acrylic acid) (PAA) and branched poly(ethylenimine) (PEI) network (PPCA hydrogel). The PPCA hydrogel provides active antibacterial function through synergic effects from protonated PEI and AgPPy nanotubes, with a tissue-like mechanical property (≈16.8 ± 4.5 kPa) and skin-like electrical conductivity (≈0.048 S m⁻¹). The tensile and shear adhesive strength (≈15.88 and ≈12.76 kPa, respectively) of the PPCA hydrogel is about two- to threefold better than that of fibrin glue. In vitro studies show the PPCA hydrogel is highly effective against both gram-positive and gram-negative bacteria. In vivo results demonstrate that the PPCA hydrogel promotes diabetic wounds with accelerated healing, with notable inflammatory reduction and prominent angiogenesis regeneration. These results suggest the PPCA hydrogel provide a promising approach to promote diabetic wound healing.