Outcomes of hyaluronan therapy in diabetic foot wounds

Recent advances in the adjunctive management of diabetic foot ulcer: Focus on noninvasive technologies

Diabetic foot ulcer (DFU) is one of the most costly and serious complications of diabetes. Treatment of DFU is usually challenging and new approaches are required to improve the therapeutic efficiencies. This review aims to update new and upcoming adjunctive therapies with noninvasive characterization for DFU, focusing on bioactive dressings, bioengineered tissues, mesenchymal stem cell (MSC) based therapy, platelet and cytokine-based therapy, topical oxygen therapy, and some repurposed drugs such as hypoglycemic agents, blood pressure medications, phenytoin, vitamins, and magnesium. Although the mentioned therapies may contribute to the improvement of DFU to a certain extent, most of the evidence come from clinical trials with small sample size and inconsistent selections of DFU patients. Further studies with high design quality and adequate sample sizes are necessitated. In addition, no single approach would completely correct the complex pathogenesis of DFU. Reasonable selection and combination of these techniques should be considered.

A focused review on hyaluronic acid contained nanofiber formulations for diabetic wound healing

The significant clinical challenge presented by diabetic wounds is due to their impaired healing process and increased risk of complications. It is estimated that a foot ulcer will develop at some point in the lives of 15-25 % of diabetic patients. Serious complications, including infection and amputation, are often led to by these wounds. In the field of tissue engineering and regenerative medicine, nanofiber-based wound dressings have emerged in recent years as promising therapeutic strategies for diabetic wound healing. Hyaluronic acid (HA), among various nanofiber materials, has gained considerable attention due to its unique properties, including biocompatibility, biodegradability, and excellent moisture retention capacity. By promoting skin hydration and controlling inflammation, a crucial role in wound healing is played by HA. Wounds are also helped to heal faster by HA through the regulation of inflammation levels and signaling the body to build more blood vessels in the damaged area. Great potential in various applications, including wound healing, has been shown by the development and use of nanofiber formulations in medicine. However, challenges and limitations associated with nanofibers in medicine exist, such as reproducibility, proper characterization, and biological evaluation. By providing a biomimetic environment that enhances re-epithelialization and facilitates the delivery of active substances, nanofibers promote wound healing. In accelerating wound healing, promising results have been shown by HA-contained nanofiber formulations in diabetic wounds. Key strategies employed by these formulations include revascularization, modulation of the inflammation microenvironment, delivery of active substances, photothermal nanofibers, and nanoparticle-loaded fabrics. Particularly crucial is revascularization as it restores blood flow to the wound area, promoting healing. Wound healing can also be enhanced by modulating the inflammation microenvironment through controlling inflammation levels. Future perspectives in this field involve addressing the current challenges and limitations of nanofiber technology and further optimizing HA-contained nanofiber formulations for improved efficacy in diabetic wound healing. This includes exploring new fabrication techniques, enhancing the biocompatibility and biodegradability of nanofibers, and developing multifunctional nanofibers for targeted drug delivery. Not only does writing a review in the field of nanofiber-based wound dressings, particularly those containing hyaluronic acid, allow us to consolidate our current knowledge and understanding but also broadens our horizons. An opportunity is provided to delve deeper into the intricacies of this innovative therapeutic strategy, explore its potential and limitations, and envision future directions. By doing so, a contribution can be made to the ongoing advancements in tissue engineering and regenerative medicine, ultimately improving the quality of life for patients with diabetic wounds.

Recent Trends in Macromolecule-Based Approaches for Hair Loss Treatment

Macromolecules are large, complex molecules composed of smaller subunits known as monomers. The four primary categories of macromolecules found in living organisms are carbohydrates, lipids, proteins, and nucleic acids; they also encompass a broad range of natural and synthetic polymers. Recent studies have shown that biologically active macromolecules can help regenerate hair, providing a potential solution for current hair regeneration therapies. This review examines the latest developments in the use of macromolecules for the treatment of hair loss. The fundamental principles of hair follicle (HF) morphogenesis, hair shaft (HS) development, hair cycle regulation, and alopecia have been introduced. Microneedle (MN) and nanoparticle (NP) delivery systems are innovative treatments for hair loss. Additionally, the application of macromolecule-based tissue-engineered scaffolds for the in vitro and in vivo neogenesis of HFs is discussed. Furthermore, a new research direction is explored wherein artificial skin platforms are adopted as a promising screening method for hair loss treatment drugs. Through these multifaceted approaches, promising aspects of macromolecules for future hair loss treatments are identified.

Nano- and Microemulsions in Biomedicine: From Theory to Practice

Nano- and microemulsions are colloidal systems that are widely used in various fields of biomedicine, including wound and burn healing, cosmetology, the development of antibacterial and antiviral drugs, oncology, etc. The stability of these systems is governed by the balance of molecular interactions between nanodomains. Microemulsions as a colloidal form play a special important role in stability. The microemulsion is the thermodynamically stable phase from oil, water, surfactant and co-surfactant which forms the surface of drops with very small surface energy. The last phenomena determines the shortage time of all fluid dispersions including nanoemulsions and emulgels. This review examines the theory and main methods of obtaining nano- and microemulsions, particularly focusing on the structure of microemulsions and methods for emulsion analysis. Additionally, we have analyzed the main preclinical and clinical studies in the field of wound healing and the use of emulsions in cancer therapy, emphasizing the prospects for further developments in this area.

General overview of biopolymers: structure and properties

Biopolymers are synthesized from a biological origin under natural phenomenon especially during their growth cycle, in the form of polymeric substances that portrays excellent properties such as flexibility, tensile strength, steadiness, reusability, and so on. The amalgamated form of two or more biopolymers leads to the formation of “biocomposites” with novel applications. Several mechanisms were identified for the effective production of biopolymers from diverse life forms such as microbial origin plant and animal origin. Based on their origin, biopolymer differs in their structure and functions. Biopolymers are preferred over chemically synthesized polymers due to their biodegradability and their impact on the environment. Biopolymers play a pivotal role in pharmaceutical industries. The biopolymers could be employed for, the administration of medicine as well as regenerative medicine to reach minimal immunogenicity and maximum pharmacological expressivity in a treated individual. Based on their properties biopolymers were exclusively used in medical devices, cosmaceuticals, and confectionaries, it is also used as additives in food industries, bio-sensors, textile industries, and wastewater treatment plants. Ecological support is of utmost concern nowadays due to the ever-expanding ramification over the planet by usage of plastic as packaging material, turning up scientists and researchers to focus on biodegradable biopolymer utilization. The miscibility-structural-property relation between every biopolymer must be focused on to improve the better environment. Specific biopolymers are designed for the betterment of agrarian and commoners of society. Advanced structural modifications, properties of biopolymers, and applications of biopolymers to achieve a greener environment were discussed in this chapter.

Growth Factor Loaded Thermo-Responsive Injectable Hydrogel for Enhancing Diabetic Wound Healing

Background: Diabetic wound (DW) is the most devastating complication resulting in significant mortality and morbidity in diabetic patients. The objective of the current study was to formulate Epidermal Growth Factor loaded Chitosan nanoparticle impregnated with thermos-responsive injectable hydrogel with protease inhibitor. EGF, shown in all stages of wound healing from inflammation to proliferation and remodelling, combined with Doxycycline, a well-known anti-inflammatory and anti-bacterial drug, could be a better strategy in diabetic wound healing. However, EGF's low stability makes it difficult to use. Methodology: The nanoparticles were prepared using the ionic gelation method. The prepared nanoparticles were evaluated for particle size, zeta potential, entrapment efficiency, and SEM studies. Further, the optimized nanoparticle batch was loaded into hydrogel with a protease inhibitor. The hydrogel was evaluated for morphology, protease degradation, in vitro drug release, anti-bacterial activity, cell migration, in vitro cell biocompatibility, and in vivo wound healing studies. Results and Conclusion: The particle size analysis of nanoparticles revealed the size (203 ± 1.236 nm), Zeta potential (+28.5 ± 1.0 mV), and entrapment efficiency of 83.430 ± 1.8%, respectively. The hydrogel showed good porous morphology, injectability, thermo-responsive, biocompatibility, and controlled drug release. In vitro anti-bacterial studies revealed the potential anti-bacterial activity of doxycycline against various microbes. In vivo data indicated that combining EGF and DOX considerably reduced inflammation time-dependent than single-agent treatment. Furthermore, histological studies corroborated these findings. After topical application of hydrogel, histopathology studies revealed significant collagen synthesis and a fully regenerated epithelial layer and advancement in all three stages (proliferation, remodelling, and maturation), which are required to improve the diabetic wound healing process by any dressing. These findings demonstrated that hydrogel promoted cutaneous wound healing in STZ-induced rats by suppressing inflammation at the wound site. Furthermore, histological studies corroborated these findings. After topical application of hydrogel, histopathology studies revealed significant collagen synthesis, a fully regenerated epithelial layer, and advancement in all three stages (proliferation, remodelling, and maturation), which are required to improve the diabetic wound healing process by any dressing. These findings demonstrated that hydrogel promoted cutaneous wound healing in STZ-induced rats by suppressing inflammation at the wound site.

Role of Nitric Oxide-Releasing Glycosaminoglycans in Wound Healing

Two glycosaminoglycan (GAG) biopolymers, hyaluronic acid (HA) and chondroitin sulfate (CS), were chemically modified via carbodiimide chemistry to facilitate the loading and release of nitric oxide (NO) to develop a multi-action wound healing agent. The resulting NO-releasing GAGs released 0.2-0.9 μmol NO mg^-1 GAG into simulated wound fluid with NO-release half-lives ranging from 20 to 110 min. GAGs containing alkylamines with terminal primary amines and displaying intermediate NO-release kinetics exhibited potent, broad spectrum bactericidal action against three strains each of Pseudomonas aeruginosa and Staphylococcus aureus ranging in antibiotic resistance profile. NO loading of the GAGs was also found to decrease murine TLR4 activation, suggesting that the therapeutic exhibits anti-inflammatory mechanisms. In vitro adhesion and proliferation assays utilizing human dermal fibroblasts and human epidermal keratinocytes displayed differences as a function of the GAG backbone, alkylamine identity, and NO-release properties. In combination with antibacterial properties, the adhesion and proliferation profiles of the GAG derivatives enabled the selection of the most promising wound healing candidates for subsequent in vivo studies. A P. aeruginosa-infected murine wound model revealed the benefits of CS over HA as a pro-wound healing NO donor scaffold, with benefits of accelerated wound closure and decreased bacterial burden attributable to both active NO release and the biopolymer backbone.

Injectable self-crosslinking hydrogels based on hyaluronic acid as vitreous substitutes

After vitrectomy, the ideal vitreous substitute should be implanted to maintain the normal function of the eye. However, the existing materials (such as silicone oil, air, perfluorocarbons, etc.) still have some shortcomings and cannot fully meet the clinical needs. In this study, thiolated hyaluronic acid (SH-HA) was prepared based on hyaluronic acid. The SH-HA hydrogel was formed by a simple transformation of the sulfhydryl group to the disulfide bond, which had high transparency, controllable swelling property, suitable mechanical strength, excellent biocompatibility and similar physical and chemical properties to natural vitreous. SH-HA hydrogel was filled into the eyes of experimental rabbits to replace their own vitreous after vitrectomy. During the 90 days follow-up period, SH-HA hydrogel showed excellent intraocular compatibility, maintained normal intraocular pressure (IOP), and no cataract, endophthalmitis, retinal detachment and other complications were observed. In general, SH-HA hydrogel has great potential as a vitreous substitute.

[Treatment of chronic hard-to-heal wounds with hyaloronic acid ester: a case series of six patients]

The treatment of chronic wounds is usually a major challenge for the involved medical staff. Various different treatment options have to be tested achieving a satisfactory result. In this retrospective case report, we describe successful treatments with hyaluronan acid ester fleece in six patients with chronic wounds of different origins. Furthermore, all patients received compression bandages or compression stockings, two patients were treated additionally with pressure relief devices and all were debrided if necessary. The chronic wounds of five out of the six patients healed completely over a period of 1.5-11 months or only with a minimal residual defect. However, one patient was still resistant to therapy over five months. In summary, the treatment with hyaluronan esters achieved good results especially in patients with complex medical history that makes a successful therapy particularly difficult.

Nitric Oxide-Releasing Hyaluronic Acid as an Antibacterial Agent for Wound Therapy

Taking advantage of their respective wound-healing roles in physiology, the dual activity of hyaluronic acid (HA) and nitric oxide (NO) was combined to create a single-agent wound therapeutic. Carboxylic acid groups of HA (6 and 90 kDa) were chemically modified with a series of alkylamines via carbodiimide chemistry to provide secondary amines for subsequent N-diazeniumdiolate NO donor formation. The resulting NO-releasing HA derivatives stored 0.3-0.6 μmol NO mg^-1 and displayed diverse release kinetics (5-75 min NO-release half-lives) under physiological conditions. The 6 kDa HA with terminal primary amines and intermediate release kinetics exhibited broad-spectrum bactericidal activity against common wound pathogens, including planktonic methicillin-resistant Staphylococcus aureus as well as planktonic and biofilm-based multidrug-resistant Pseudomonas aeruginosa. The treatment of infected murine wounds with NO-releasing HA facilitated more rapid wound closure and decreased the quantity of the P. aeruginosa genetic material in the remaining wound tissue. Hyaluronidase readily degraded the HA derivatives, indicating that NO donor modification did not prohibit endogenous biodegradation pathways.

Glycemic control and diabetic foot ulcer outcomes: A systematic review and meta-analysis of observational studies

OBJECTIVE

To evaluate the association between glycemic control (hemoglobin A1C, fasting glucose, and random glucose) and the outcomes of wound healing and lower extremity amputation (LEA) among patients with diabetic foot ulcers (DFUs).

RESEARCH DESIGN AND METHODS

Medline, EMBASE, Cochrane Library, and Scopus were searched for observational studies published up to March 2019. Five independent reviewers assessed in duplicate the eligibility of each study based on predefined eligibility criteria and two independent reviewers assessed risk of bias. Ameta-analysis was performed to calculate a pooled odds ratio (OR) or hazard ratio (HR) using random effects for glycemic measures in relation to the outcomes of wound healing and LEA. Subgroup analyses were conducted to explore potential source of heterogeneity between studies. The study protocol is registered with PROSPERO (CRD42018096842).

RESULTS

Of 4572 study records screened, 60 observational studies met the study eligibility criteria of which 47 studies had appropriate data for inclusion in one or more meta-analyses(n = 12,604 DFUs). For cohort studies comparing A1C >7.0 to 7.5% vs. lower A1C levels, the pooled OR for LEA was 2.04 (95% CI, 0.91, 4.57) and for studies comparing A1C ≥ 8% vs. <8%, the pooled OR for LEA was 4.80 (95% CI 2.83, 8.13). For cohort studies comparing fasting glucose ≥126 vs. <126 mg/dl, the pooled OR for LEA was 1.46 (95% CI, 1.02, 2.09). There was no association with A1C category and wound healing (OR or HR). There was high risk of bias with respect to comparability of cohorts as many studies did not adjust for potential confounders in the association between glycemic control and DFU outcomes.

CONCLUSIONS

Our findings suggest that A1C levels ≥8% and fasting glucose levels ≥126 mg/dl are associated with increased likelihood of LEA in patients with DFUs. A purposively designed prospective study is needed to better understand the mechanisms underlying the association between hyperglycemia and LEA.

Hyaluronic Acid-Povidone-Iodine Compound Facilitates Diabetic Wound Healing in a Streptozotocin-Induced Diabetes Rodent Model

BACKGROUND

This study investigated whether a hyaluronic acid-povidone-iodine compound can enhance diabetic wound healing.

METHODS

A dorsal skin defect (6 × 5 cm) in a streptozotocin-induced diabetes rodent model was used. Seventy male Wistar rats were divided into seven groups: I, normal control; II, diabetic control, no treatment; III, diabetic rats, lower molecular weight (100 kDa) hyaluronic acid; IV, rats, higher molecular weight (1000 kDa) hyaluronic acid; V, rats, 0.1% povidone-iodine; VI, rats, lower molecular weight hyaluronic acid plus povidone-iodine; and VII, rats, higher molecular weight hyaluronic acid plus povidone-iodine. Histologic examination was performed with hematoxylin and eosin staining. CD45, Ki-67, prolyl 4-hydroxylase, and vascular endothelial growth factor were evaluated with immunohistochemical staining.

RESULTS

Compared with the control, higher molecular weight hyaluronic acid plus povidone-iodine-treated rats had significantly reduced wound area (p < 0.001). Higher molecular weight hyaluronic acid plus povidone-iodine increased wound healing time when compared with higher molecular weight hyaluronic acid, povidone-iodine, or lower molecular weight hyaluronic acid plus povidone-iodine. Histology revealed significantly increased neovessels and suppressed inflammatory response in the higher molecular weight hyaluronic acid plus povidone-iodine group when compared with the control group. Immunohistochemical staining revealed significantly increased Ki67, prolyl 4-hydroxylase, and vascular endothelial growth factor expression, and suppressed CD45 expression in the higher molecular weight hyaluronic acid plus povidone-iodine group when compared with the other groups.

CONCLUSION

Higher molecular weight hyaluronic acid plus povidone-iodine complex dressing significantly facilitated diabetic wound healing via increasing neovascularization and tissue regeneration and suppressing a proinflammatory response.

Comblike Ionic Complexes of Hyaluronic Acid and Alkanoylcholine Surfactants as a Platform for Drug Delivery Systems

Nontoxic alkanoylcholine soaps ( nACh) were synthesized from choline and fatty acids with numbers of carbons n equal to 12, 14, 16, and 18, the latter including both saturated and 9- cis unsaturated alkanoyl chains. Coupling of nACh with hyaluronic acid (HyA) rendered comblike ionic complexes nACh·HyA that were non-water-soluble. The complexes were thermally stable up to temperatures above 200 °C but readily degraded by water, in particular when hyaluronidases were present in the aqueous medium. In the solid state, these complexes were self-assembled in a biphasic layered structure in which the surfactant and the polysaccharide phases were alternating regularly with a periodicity dependent on the length of the alkanoyl chain. The paraffinic phase was found to be crystallized in saturated complexes with n ≥ 14, but only 18ACh·HyA showed reversible melting crystallization when subjected to cyclic heating-cooling treatment. Nanoparticles with diameters in the 50-150 nm range were prepared by ionotropic gelation from unbalanced 18ACh·HyA complexes with surfactant:HyA ratios of 0.5 and 0.25. These nanoparticles were also structured in layers, swelled slowly in water, and shown to be noncytotoxic in in vitro assays against macrophages cells. It was also shown that the anticancer drug doxorubicin was efficiently encapsulated in both films and NPs of 18ACh·HyA, and its release was shown to be almost linear and complete after one day of incubation in physiological medium. The nACh·HyA complexes constitute a highly promising biocompatible/biodegradable platform for the design of systems suitable for drug transport and targeting delivery in anticancer chemotherapy.

MitoQ Loaded Chitosan-Hyaluronan Composite Membranes for Wound Healing

Two self-associating biopolymers, namely chitosan (Ch) and a high-molar-mass hyaluronan (HA), were used to prepare membranes with the aim to protect and to enhance the healing of injured skin. A mitochondrially-targeted antioxidant—MitoQ—was incorporated into the mixture of biopolymers prior to their self-association. These three-component membranes were evaluated in detail utilising surface roughness measurements, contact angle measurements, hemocompatibility, and thrombogenicity analyses. Furthermore, in vivo application of Ch/HA/MitoQ membranes was assessed on injured rabbit and rat skin utilizing histological methods. The results showed that the prepared thrombogenic Ch/HA/MitoQ membranes had higher roughness, which allowed for greater surface area for tissue membrane interaction during the healing processes, and lower cytotoxicity levels than controls. MitoQ-loaded composite membranes displayed superior healing properties in these animal models compared to control membranes.

Hyaluronic acid dressing (Healoderm) in the treatment of diabetic foot ulcer: A prospective, randomized, placebo-controlled, single-center study

Fast and complete healing of a diabetic foot ulcer (DFU) is challenging due to the hostile wound healing environment of the diabetic patients. As a part of a multimodal treatment approach, advanced dressing material using hyaluronic acid (HA) has been found to be effective. However, previous studies have used HA with additional biologics, which interferes in determining the true clinical effect of HA in DFU. To examine the sole effectiveness of HA in DFU treatment, a prospective, randomized, placebo-controlled, single-center study was conducted using an HA dressing without additional substances. Thus, 34 patients who met the inclusion criteria were randomized into two groups (the study group: HA dressing material; the control group: conventional dressing material). During the 12-week study period, complete ulcer healing rate was evaluated as a primary endpoint. Additionally, healing velocity and the mean duration for achieving a 50% ulcer size reduction was compared between the two groups as a secondary endpoint. At the end of the study, the study group presented a significantly higher complete healing rate as compared to that in the control group [84.6% (11/13), 41.6% (5/12), respectively, P = 0.041]. Additionally, faster ulcer healing velocity and shorter mean duration for achieving a 50% ulcer size reduction were observed in the study group (P = 0.022 and 0.004, respectively). The Kaplan-Meier survival analysis for the median time for 50% ulcer healing rate also showed a significantly shorter duration in the study group (21 days vs. 39 days, P = 0.0127). Finally, there were no adverse events related to the dressing materials used in the study. As a major component of the extracellular matrix, this study supports the safety and efficacy of a pure HA dressing without additional substances in treating DFU.

Layer-by-Layer (LBL) Self-Assembled Biohybrid Nanomaterials for Efficient Antibacterial Applications

Although antibiotics have been widely used in clinical applications to treat pathogenic infections at present, the problem of drug-resistance associated with abuse of antibiotics is becoming a potential threat to human beings. We report a biohybrid nanomaterial consisting of antibiotics, enzyme, polymers, hyaluronic acid (HA), and mesoporous silica nanoparticles (MSNs), which exhibits efficient in vitro and in vivo antibacterial activity with good biocompatibility and negligible hemolytic side effect. Herein, biocompatible layer-by-layer (LBL) coated MSNs are designed and crafted to release encapsulated antibiotics, e.g., amoxicillin (AMO), upon triggering with hyaluronidase, produced by various pathogenic Staphylococcus aureus (S. aureus). The LBL coating process comprises lysozyme (Lys), HA, and 1,2-ethanediamine (EDA)-modified polyglycerol methacrylate (PGMA). The Lys and cationic polymers provided multivalent interactions between MSN-Lys-HA-PGMA and bacterial membrane and accordingly immobilized the nanoparticles to facilitate the synergistic effect of these antibacterial agents. Loading process was characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction spectroscopy (XRD). The minimal inhibition concentration (MIC) of MSN-Lys-HA-PGMA treated to antibiotic resistant bacteria is much lower than that of isodose Lys and AMO. Especially, MSN-Lys-HA-PGMA exhibited good inhibition for pathogens in bacteria-infected wounds in vivo. Therefore, this type of new biohybrid nanomaterials showed great potential as novel antibacterial agents.

The preparation, characterization and evaluation of regenerated cellulose/collagen composite hydrogel films

Porous structured regenerated cellulose films were oxidized by periodate oxidation to obtain 2,3-dialdehyde cellulose (DARC) films, which were then reacted with collagen to obtain DARC/Col composite films. The subsequent FT-IR spectra indicated that collagen was immobilized on the DARC matrix via the Schiff base reaction between NH2 in collagen and CHO in DARC backbone. Scanning electron microscopy revealed that DARC/Col exhibited a refined 3D network structure and its porosity and pore size decreased with increasing of collagen concentration. The composite films demonstrated a good equilibrium-swelling ratio, air permeability and water retention properties. The composite films also showed excellent mechanical properties, which was vital for practical application. Finally, the cytotoxicity of the composite film was evaluated using NIH3T3 mice fibroblast cells, the results revealed that DARC/Col composite films have good biocompatibility for use as scaffold material in tissue engineering.

Hyaluronan and synovial joint: function, distribution and healing

Synovial fluid is a viscous solution found in the cavities of synovial joints. The principal role of synovial fluid is to reduce friction between the articular cartilages of synovial joints during movement. The presence of high molar mass hyaluronan (HA) in this fluid gives it the required viscosity for its function as lubricant solution. Inflammation oxidation stress enhances normal degradation of hyaluronan causing several diseases related to joints. This review describes hyaluronan properties and distribution, applications and its function in synovial joints, with short review for using thiol compounds as antioxidants preventing HA degradations under inflammation conditions.

Recent advances on the development of wound dressings for diabetic foot ulcer treatment--a review

Diabetic foot ulcers (DFUs) are a chronic, non-healing complication of diabetes that lead to high hospital costs and, in extreme cases, to amputation. Diabetic neuropathy, peripheral vascular disease, abnormal cellular and cytokine/chemokine activity are among the main factors that hinder diabetic wound repair. DFUs represent a current and important challenge in the development of novel and efficient wound dressings. In general, an ideal wound dressing should provide a moist wound environment, offer protection from secondary infections, remove wound exudate and promote tissue regeneration. However, no existing dressing fulfills all the requirements associated with DFU treatment and the choice of the correct dressing depends on the wound type and stage, injury extension, patient condition and the tissues involved. Currently, there are different types of commercially available wound dressings that can be used for DFU treatment which differ on their application modes, materials, shape and on the methods employed for production. Dressing materials can include natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the form of films, foams, hydrocolloids and hydrogels. Moreover, wound dressings may be employed as medicated systems, through the delivery of healing enhancers and therapeutic substances (drugs, growth factors, peptides, stem cells and/or other bioactive substances). This work reviews the state of the art and the most recent advances in the development of wound dressings for DFU treatment. Special emphasis is given to systems employing new polymeric biomaterials, and to the latest and innovative therapeutic strategies and delivery approaches.

Hyaluronic acid derivatives and their healing effect on burns, epithelial surgical wounds, and chronic wounds: a systematic review and meta-analysis of randomized controlled trials

Hyaluronic acid (HA) is a polysaccharide common to most species and is found in many sites in the human body, including the skin and soft tissue. A systematic review of the literature and meta-analysis was performed to identify randomized controlled trials, evaluating the use of HA derivatives in healing burns, epithelial surgical, and chronic wounds. Nine studies were identified, which met the search criteria and clinical endpoints of complete healing and percent wound size reduction when using HA vs. either an active or passive comparator. It was found in the vast majority of randomized controlled trials (eight of nine) that HA derivatives significantly improved the healing of wounds vs. traditional therapies or placebo (either via complete healing or a significant reduction in wound size) occurring from burns, venous insufficiency, diabetes, neuropathic insufficiency, and surgical removal of the epithelial layer (for tattoo removal). In the other remaining trial, one formulation of HA was compared with another, with the higher concentration showing improved application characteristics. Further, it was found in a meta-analysis in subsets of patients with diabetic foot ulcers (neuropathic) that HA derivatives healed these types of wounds significantly faster than standard of care. These studies in aggregate show that HA derivatives accelerate the healing process in burns, epithelial surgical wounds, and chronic wounds.

Influence of hyaluronic acid on bacterial and fungal species, including clinically relevant opportunistic pathogens

Hyaluronic acid (HA) has several clinical applications (aesthetic surgery, dermatology, orthopaedics and ophtalmology). Following recent evidence, suggesting antimicrobial and antiviral properties for HA, we investigated its effects on 15 ATCC strains, representative of clinically relevant bacterial and fungal species. The in vitro system employed allowed to assess optical density of broth cultures as a measure of microbial load in a time-dependent manner. The results showed that different microbial species and, sometimes, different strains belonging to the same species, are differently affected by HA. In particular, staphylococci, enterococci, Streptococcus mutans, two Escherichia coli strains, Pseudomonas aeruginosa, Candida glabrata and C. parapsilosis displayed a HA dose-dependent growth inhibition; no HA effects were detected in E. coli ATCC 13768 and C. albicans; S. sanguinis was favoured by the highest HA dose. Therefore, the influence of HA on bacteria and fungi warrants further studies aimed at better establishing its relevance in clinical applications.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

The role of CD44 in cutaneous inflammation

CD44 is a transmembrane glycoprotein expressed in various tissues including the skin. Previous studies indicated that CD44 is required for epidermal permeability barrier homeostasis and keratinocyte differentiation. Yet, while some studies have demonstrated that CD44 is critical for the development of inflammation, others have shown that CD44 is not essential for the development of cutaneous inflammation. In this study, we evaluated the changes in epidermal CD44 expression in a variety of skin inflammatory models and determined whether CD44 is required for the development of cutaneous inflammation. Inflammatory responses were compared in CD44 KO versus wild-type mice in acute models of irritant and allergic contact dermatitis, as well as in a subacute allergic contact dermatitis induced by repeated hapten treatment. Inflammatory responses were assessed by measuring ear thickness and epidermal hyperplasia in haematoxylin & eosin-stained sections. Our results demonstrate that: (i) epidermal CD44 expression increases in both acute and subacute cutaneous inflammatory models; and (ii) acute disruption of the epidermal permeability barrier function increases epidermal CD44 expression. Whereas inflammatory responses did not differ between CD44 KO and wild-type mice in acute models of irritant and allergic contact dermatitis, both inflammatory responses and epidermal hyperplasia increased in CD44 KO mice following repeated hapten challenges. These results show first, that permeability barrier disruption and inflammation stimulate epidermal CD44 expression, and second, that CD44 modulates epidermal proliferation and inflammatory responses in a subacute murine allergic contact dermatitis model.

The diabetic foot

Diabetes is reaching epidemic proportions and with it carries the risk of complications. Disease of the foot is among one of the most feared complications of diabetes. The ultimate endpoint of diabetic foot disease is amputation, which is associated with significant morbidity and mortality, besides having immense social, psychological and financial consequences. As the majority of amputations are preceded by foot ulceration, it is crucial to identify those at an increased risk. Diabetic foot ulcers may develop as a result of neuropathy, ischaemia or both and when infection complicates a foot ulcer, the combination can become limb and life threatening. Structural abnormalities such as calluses, bunions, hammer toes, claw toes, flat foot and rocker bottom foot need to be identified and managed.

Modification of collagen formation using supplemented mesh materials

BACKGROUND

Formation of recurrent inguinal and incisional hernia shows an underlying defect in the wound healing process. Even following mesh repair an altered collagen formation and insufficient mesh integration has been found as main reason for recurrences. Therefore the development of bioactive mesh materials to achieve a local modification of the scar formation to improve patients outcome is advisable.

METHODS

Thirty-six male Wistar rats were used within this study. A Mersilene (R) mesh sample was implanted after midline skin incision and subcutaneous preparation. Before implantation mesh samples were incubated for 30 minutes with either one of the following agents: doxycycline, TGF-beta 3, zinc-hydrogeneaspartate, ascorbic acid, hyaluronic acid. Incubation with a physiologic 0.9 % NaCl solution served as control. Seven and 90 days after mesh implantation 3 animals from each group (n = 6) were sacrificed for morphological observations. Collagen quantity and quality was analyzed measuring the collagen/protein as well as the collagen type I/III ratio.

RESULTS

Following an implantation interval of 90 days supplementation with doxycycline (39.3 +/- 7.0 microg/mg) and hyaluronic acid (34.4 +/- 5.8 microg/mg) were found to have a significantly increased collagen/protein ratio compared to implantation of the pure Mersilene (R) mesh samples (28.3 +/- 1.9 microg/mg). Furthermore, an overall increase of the collagen type I/III ratio was found in all groups indicating scar maturation over time. However, no significant differences were found after 7 and 90 days of implantation comparing collagen type I/III ratio of supplemented mesh samples and control group.

CONCLUSIONS

In summary, we found an influence of supplemented mesh materials on collagen deposition. However, the investigated bioactive agents with reported influence on wound healing were not associated with an improved quality in scar formation.

The extracellular matrix in wound healing: a closer look at therapeutics for chronic wounds

Disappointing results with the use of exogenous recombinant growth factors in chronic wounds have redirected the focus to the extracellular matrix (ECM). Newer research has clearly changed our view on the role of the ECM in tissue repair and dismissed the dogma that the sole function of ECM is a passive physical support for cells. It is now clear that intact or fragmented ECM molecules are capable of transducing signals pivotal for cell processes in wound healing primarily via integrin interactions in concert with growth factor activation. In addition, our knowledge about ECM molecules in minute concentrations with biological activity, but devoid of significant structural influence, is increasing. This article reviews the multifaceted molecular roles of ECM in the normal wound-healing process and some molecular abnormalities in chronic wounds, and touches on potential therapies based on the developments of tissue biology.

Hyaluronic acid: the scientific and clinical evidence

Hyaluronic acid is a naturally occurring biopolymer whose molecular structure is highly conserved between mammalian species. First described in 1934, it has since been used across a wide variety of medical fields as diverse as neurosurgery and cutaneous wound healing. Presently it has reached prominence in cosmetic practice where it is now the injectable dermal filler of choice for most surgeons. We used our experience of this technology with searches in the English language literature for the purpose of a systematic review. We present an overview, including the scientific evidence for its use in wound healing and, briefly, in other fields. We summarise the evidence for and against hyaluronic acid and provide a resumé of the current technologies available in fields such as skin regeneration and wound healing, in addition to cosmetic surgery. This overview is not intended to teach the reader about the various formulations currently on the market or how to use these materials clinically - rather to provide a solid scientific background enabling the reader to understand the attributes (and otherwise) of the material. We hope to allow clinicians to assess the evidence for a material now in common use in order that they may be fully aware of its properties.

Prospective randomized controlled study of Hydrofiber dressing containing ionic silver or calcium alginate dressings in non-ischaemic diabetic foot ulcers

AIMS

Diabetic foot ulcers (DFUs) are at risk of infection and impaired healing, placing patients at risk of lower extremity amputation. DFU care requires debridement and dressings. A prospective, multicentre study compared clinical efficacy and safety of AQUACEL Hydrofiber dressings containing ionic silver (AQAg) with those of Algosteril calcium alginate (CA) dressings in managing out-patients with Type 1 or 2 diabetes mellitus and non-ischaemic Wagner Grade 1 or 2 DFUs.

METHODS

Patients stratified by antibiotic use on enrolment were randomly assigned to similar protocols including off-loading, AQAg (n = 67) or CA (n = 67) primary dressings and secondary foam dressings for 8 weeks or until healing. Clinical efficacy measures were healing outcomes and primarily healing speed. Adverse events were recorded.

RESULTS

AQAg and CA groups were comparable at baseline. All ulcer healing outcomes improved in both groups. The mean time to healing was 53 days for AQAg ulcers and 58 days for CA ulcers (P = 0.34). AQAg-treated ulcers reduced in depth nearly twice as much as CA-treated ulcers (0.25 cm vs. 0.13 cm; P = 0.04). There was more overall ulcer improvement and less deterioration in AQAg subjects (P = 0.058), particularly in the subset initially using antibiotics (P = 0.02). Safety profiles of both groups were similar.

CONCLUSION

When added to standard care with appropriate off-loading, AQAg silver dressings were associated with favourable clinical outcomes compared with CA dressings, specifically in ulcer depth reduction and in infected ulcers requiring antibiotic treatment. This study reports the first significant clinical effects of a primary wound dressing containing silver on DFU healing.

Emerging drugs for diabetic foot ulcers

Diabetic foot ulceration results from factors extrinsic to the foot such as repeated trauma, ischaemia and infection, as well as intrinsic factors that lead to impairment of wound healing. Intrinsic factors are less well understood, but include deficiency of growth factors, changes in extracellular matrix components with excess proteases, reduced fibroblast activity, cellular abnormalities, deficiencies of angiogenesis, nitric oxide abnormalities and hyperglycaemia. The scientific rationale of therapy is to correct both the external factors that cause diabetic foot ulcers and the internal factors that lead to impairment of wound healing. Current research is leading to new therapies that can be divided into the following classes: growth factors, skin substitutes, extracellular matrix proteins, stem cell therapy, gene therapy, protease inhibitors, angiogenesis stimulants, nitric oxide-releasing agents, adenosine agonists, immunostimulants, vasoactive compounds and granulating agents. These therapies should be considered when existing treatments to correct extrinsic factors have failed to heal ulceration in the diabetic foot.

Hyaluronan: pharmaceutical characterization and drug delivery

Hyaluronic acid (HA), is a polyanionic polysaccharide that consists of N-acetyl-D-glucosamine and beta-glucoronic acid. It is most frequently referred to as hyaluronan because it exists in vivo as a polyanion and not in the protonated acid form. HA is distributed widely in vertebrates and presents as a component of the cell coat of many strains of bacteria. Initially the main functions of HA were believed to be mechanical as it has a protective, structure stabilizing and shock-absorbing role in the body. However, more recently the role of HA in the mediation of physiological functions via interaction with binding proteins and cell surface receptors including morphogenesis, regeneration, wound healing, and tumor invasion, as well as in the dynamic regulation of such interactions on cell signaling and behavior has been documented. The unique viscoelastic nature of hyaluronan along with its biocompatibility and nonimmunogenicity has led to its use in a number of cosmetic, medical, and pharmaceutical applications. More recently, HA has been investigated as a drug delivery agent for ophthalmic, nasal, pulmonary, parenteral, and dermal routes. The purpose of our review is to describe the physical, chemical, and biological properties of native HA together with how it can be produced and assayed along with a detailed analysis of its medical and pharmaceutical applications.

The role of hyaluronic acid in wound healing: assessment of clinical evidence

Hyaluronic acid (hyaluronan), a naturally occurring polymer within the skin, has been extensively studied since its discovery in 1934. It has been used in a wide range of medical fields as diverse as orthopedics and cosmetic surgery, but it is in tissue engineering that it has been primarily advanced for treatment. The breakdown products of this large macromolecule have a range of properties that lend it specifically to this setting and also to the field of wound healing. It is non-antigenic and may be manufactured in a number of forms, ranging from gels to sheets of solid material through to lightly woven meshes. Epidermal engraftment is superior to most of the available biotechnologies and, as such, the material shows great promise in both animal and clinical studies of tissue engineering. Ongoing work centers around the ability of the molecule to enhance angiogenesis and the conversion of chronic wounds into acute wounds.

Hyaluronic acid: a unique topical vehicle for the localized delivery of drugs to the skin

Hyaluronic acid (HA) is a naturally occurring polyanionic, polysaccharide that consists of N-acetyl-D-glucosamine and beta-glucoronic acid. It is present in the intercellular matrix of most vertebrate connective tissues especially skin where it has a protective, structure stabilizing and shock-absorbing role. The unique viscoelastic nature of HA along with its biocompatibility and non-immunogenicity has led to its use in a number of clinical applications, which include: the supplementation of joint fluid in arthritis; as a surgical aid in eye surgery; and to facilitate the healing and regeneration of surgical wounds. More recently, HA has been investigated as a drug delivery agent for various routes of administration, including ophthalmic, nasal, pulmonary, parenteral and topical. In fact, regulatory approval in the USA, Canada and Europe was granted recently for 3% diclofenac in 2.5% HA gel, Solaraze, for the topical treatment of actinic keratoses, which is the third most common skin complaint in the USA. The gel is well tolerated, safe and efficacious and provides an attractive, cost-effective alternative to cryoablation, curettage or dermabrasion, or treatment with 5-fluorouracil. The purpose of this review is to describe briefly the physical, chemical and biological properties of HA together with some details of its medical and pharmaceutical uses with emphasis on this more recent topical application.

Hyaluronic acid in the treatment and prevention of skin diseases: molecular biological, pharmaceutical and clinical aspects

The glycosaminoglycan hyaluronic acid (HA), or hyaluronan, is a major component of the extracellular matrix of skin, joints, eye and many other tissues and organs. In spite of its simple structure, HA demonstrates remarkable rheological, viscoelastic and hygroscopic properties which are relevant for dermal tissue function. Biological activities in skin, however, are also due to its interaction with various binding proteins (hyaladherins). Due to an influence on signaling pathways, HA is involved in the wound-healing process and scarless fetal healing. Increased HA concentrations have been associated with inflammatory skin diseases. In clinical trials, topical application of HA improved wound healing; in particular, acute radioepithelitis, venous leg ulcers or diabetic foot lesions responded to HA treatment. Moreover, as a topical drug delivery system for diclofenac, an HA gel has recently been approved for the treatment of actinic keratoses. Finally, chemical modifications led to new HA derivates and biomaterials, which may be introduced into therapy in the future. Therefore, ongoing research offers new horizons for the therapeutic use of this glycosaminoglycan which has been regarded as an inert structural component until recently.

New and experimental approaches to treatment of diabetic foot ulcers: a comprehensive review of emerging treatment strategies

Diabetic foot ulcers occur in up to 15% of all diabetic patients and are a leading cause of nontraumatic amputation worldwide. Neuropathy, abnormal foot biomechanics, peripheral vascular disease and external trauma are the major contributors to the development of a foot ulcer in the diabetic patient. Therapy today includes repeated debridement, offloading, and dressings, for lower grade ulcers, and broad spectrum antibiotics and occasionally limited or complete amputation for higher grades, requiring a team effort of health care workers from various specialties. The large population affected by diabetic foot ulcers and the high rates of failure ending with amputation even with the best therapeutic regimens, have resulted in the development of new therapies and are the focus of this review. These include new off loading techniques, dressings from various materials, methods to promote wound closure using artificial skin grafts, different growth factors or wound bed modulators and methods of debridement. These new techniques are promising but still mostly unproven and traditional approaches cannot be replaced. New and generally more expensive therapies should be seen as adding to traditional approaches.

An evaluation of Hyalofill-F plus compression bandaging in the treatment of chronic venous ulcers

OBJECTIVE

Hyaluronan, a component of the extracellular matrix, plays a significant role in several aspects of tissue repair and the wound healing process.

METHOD

In this Italian study Hyalofill-F, a partial benzyl ester derivative of hyaluronan, used in combination with compression bandaging, was compared with the well-established therapy in Italy of non-adherent gauze plus compression therapy in the treatment of chronic venous leg ulcers.

RESULTS

Hyalofill-F plus compression bandaging performed significantly better than non-adherent gauze plus compression bandage in all of the clinically relevant efficacy parameters. Mean reduction in ulcer area in the hyaluronan-derivative group was 8.1 cm2 after eight weeks of treatment, compared with 0.4 cm2 in the comparator group. The resulting difference of 7.7 cm2 between the two groups was statistically significant (p = 0.0019). Furthermore, statistically significant results in favour of the hyaluronan-derivative group were obtained in the following: speed of epithelialisation; leveling of the margins; degree of maceration; pain intensity and frequency.

CONCLUSION

Hyalofill-F plus compression bandaging resulted in an earlier and greater decrease in ulcer area compared with non-adherent gauze plus compression bandaging, therapy supporting its use in the treatment of chronic venous ulcers.

A trial to assess the efficacy and tolerability of Hyalofill-F in non-healing venous leg ulcers

OBJECTIVE

This single-centre, open, uncontrolled pilot clinical trial set out to assess the efficacy and tolerability of Hyalofill-F (a partial benzyl ester derivative of hyaluronan), used in combination with compression bandaging, in the treatment of venous leg ulcers.

METHOD

The 20 patients enrolled into the study had venous insufficiency and a leg ulcer that had been refractory to treatment for one month. Treatment was continued for eight weeks, with weekly assessments.

RESULTS

During the study period four of the patients' ulcers healed completely. An average wound area reduction of 53.5% was seen in the ulcers that did not heal. Differences in ulcer area and ulcer depth between the initial and final visit were significant (p < 0.01, p = 0.03). The average healing rate (cm2/week reduction) was 1.26 +/- 1.7 (standard deviation). A calculated prognostic index was used to identify patients at high risk of a poor response to compression therapy (10% probability of wound closure at 120 weeks). These patients demonstrated a mean 63% decrease in wound area after eight weeks of treatment with Hyalofill-F plus compression bandaging. All wounds showed a positive response in terms of granulation-tissue formation. The comfort of the dressing was described as excellent.

CONCLUSION

The hyaluronan derivative showed promising results in initiating the healing process in chronic venous ulcers. It was found to be well tolerated and safe to use. However, further clinical trials should be performed involving a control group to verify these data.

DECLARATION OF INTEREST

This study was sponsored by Fidia Advanced Biopolymers, Italy.