Advanced Therapeutic Dressings for Effective Wound Healing--A Review

Fabrication of ascorbyl palmitate loaded poly(caprolactone)/silver nanoparticle embedded poly(vinyl alcohol) hybrid nanofibre mats as active wound dressings via dual-spinneret electrospinning

AP loaded PCL/AgNP embedded PVA hybrid nanofibre mats were prepared through dual-spinneret electrospinning, which altogether contributed to wound healing.

Mussel-inspired hydrogel tissue adhesives for wound closure

Tissue adhesives have been introduced as a promising alternative for the traditional wound closure method of suturing.

pH-Modulating Poly(ethylene glycol)/Alginate Hydrogel Dressings for the Treatment of Chronic Wounds

The development of chronic wounds has been frequently associated with alkaline pH values. The application of pH-modulating wound dressings can, therefore, be a promising treatment option to promote normal wound healing. This study reports on the development and characterization of acidic hydrogel dressings based on interpenetrating poly(ethylene glycol) diacrylate/acrylic acid/alginate networks. The incorporation of ionizable carboxylic acid groups results in high liquid uptake up to 500%. The combination of two separate polymer networks significantly improves the tensile and compressive stability. In a 2D cell migration assay, the application of hydrogels (0% to 1.5% acrylic acid) results in complete "wound" closure; hydrogels with 0.25% acrylic acid significantly increase the cell migration velocity to 19.8 ± 1.9 µm h^-1 . The most promising formulation (hydrogels with 0.25% acrylic acid) is tested on 3D human skin constructs, increasing keratinocyte ingrowth into the wound by 164%.

Germicide wound pad with active, in situ, electrolytically produced hypochlorous acid

We describe a new wound dressing technology that can actively generate an inorganic germicide agent, in situ, within the wound pad. The technology provides real time control over the quantitative, spatial and temporal delivery of the germicide. The identity of the germicide is hypochlorous acid (HClO). The HClO is produced in a flexible wound pad, made of a composite of thin (micrometer scale) layers of various materials, with different electrochemical properties that enhance HClO production. Active control over the production of HClO is achieved by control of the pH and of the electric potential across the layers. The effectiveness of the Active HClO Pad (AHClOP) concept is demonstrated in a study on sterilization of E. coli in a deep wound contamination simulating gel. The performance of the AHClOP is compared with that of four commercial wound dressings. Results show that the AHClOP can sterilize throughout the gel, while the commercial dressings cannot.

Controlled local drug delivery strategies from chitosan hydrogels for wound healing

INTRODUCTION

The main target of tissue engineering is the preparation and application of adequate materials for the design and production of scaffolds, that possess properties promoting cell adhesion, proliferation and differentiation. The use of natural polysaccharides, such as chitosan, to prepare hydrogels for wound healing and controlled drug delivery is a research topic of wide and increasing interest. Areas covered: This review presents the latest results and challenges in the preparation of chitosan and chitosan-based scaffold/hydrogel for wound healing applications. A detailed overview of their behavior in terms of controlled drug delivery, divided by drug categories, and efficacy was provided and critically discussed. Expert opinion: The need to establish and exploit the advantages of natural biomaterials in combination with active compounds is playing a pivotal role in the regenerative medicine fields. The challenges posed by the many variables affecting tissue repair and regeneration need to be standardized and adhere to recognized guidelines to improve the quality of evidence in the wound healing process. Currently, different methodologies are followed to prepare innovative scaffold formulations and structures. Innovative technologies such as 3D printing or bio-electrospray are promising to create chitosan-based scaffolds with finely controlled structures with customizable shape porosity and thickness. Chitosan scaffolds could be designed in combination with a variety of polysaccharides or active compounds with selected and reproducible spacial distribution, providing active wound dressing with highly tunable controlled drug delivery.

Efficacy of Trans-cinnamaldehyde and Eugenol in Reducing Acinetobacter baumannii Adhesion to and Invasion of Human Keratinocytes and Controlling Wound Infection In Vitro

The study investigated the efficacy of two natural, plant-derived antimicrobials (PDAs), namely trans-cinnamaldehyde (TC), and eugenol (EG) for decreasing Acinetobacter baumannii adhesion to and invasion of human keratinocytes (HEK001). Moreover, the efficacy of two PDAs for inhibiting A. baumannii biofilm formation was determined using an in vitro collagen matrix wound model. Additionally, the effect of TC and EG on A. baumannii biofilm architecture was visualized using confocal scanning microscopy. Further the effect of both PDAs on genes critical for biofilm synthesis was determined using real-time quantitative polymerase chain reaction. Both TC and EG significantly reduced A. baumannii adhesion and invasion to HEK001 by ~2 to 3 log₁₀ CFU/mL (p < 0.05) compared with the controls (p < 0.05). Further, after 24 and 48 h, TC and EG inhibited biofilm formation by ~1.5 to 2 and ~2 to 3.5 log₁₀ CFU/mL, compared with controls (p < 0.05). Confocal microscopy revealed that TC and EG disrupted the biofilm architecture. RT-qPCR results indicated that two phytochemicals significantly down-regulated the transcription of genes associated with A. baumannii biofilm production. The results suggest that both TC and EG could potentially be used to treat A. baumannii wound infections; however, their efficacy in in vivo models needs to be validated. Copyright © 2016 John Wiley & Sons, Ltd.

Cytotoxic and Nitric Oxide Inhibition Activities of Propolis Extract along with Microencapsulation by Complex Coacervation

In this study, cytotoxicity of ethanol extract of propolis (EEP) originating from Sivas, Turkey was screened against several cancer cell lines, namely PC-3, U87MG, A-549, mPANC96, CaCo-2, MCF-7, HeLa, MDA-MB-231 and a non-tumor cell line HEK293 by MTT assay. The inhibition levels of inducible nitric oxide synthase (iNOS) were also determined by using RAW 264.7 macrophage cells following lipopolysaccharide (LPS) treatment. EEP exhibited significant cytotoxic nitric oxide inhibition activities with an IC50 value of 0.1 ± 0.1 μg/ml indicating a high potential as an anti-inflammatory agent. In spite of these promising results and the fact that propolis is a highly nutritive substance, its low solubility and bitter taste limit the applications as a natural supplement. Encapsulation might serve as a good strategy in order to overcome these problems. Complex coacervation was applied where the main focus was on surfactant type, polymer ratio (alginate:gelatin), stirring rate and concentration of core material. The mean particle size of unloaded microparticles were 22.62 μm obtained with gelatin:alginate ratio of 1:1 at a stirring rate of 1400 rpm with 2 ml of 1 % (w/v) sodium carboxymethyl cellulose (Na-CMC), whereas addition of EEP at a concentration of 100 mg/ml increased the mean particle size to 36.44 μm and yielded an encapsulation efficiency of 98.77 %. The cytotoxicities of EEP loaded microparticles were also assessed both on MCF-7 and MDA-MB-231 where similar results were achieved as free EEP which can enhance the possible use of propolis extract in the industry as a natural supplement.

Biochemical and Biophysical Cues in Matrix Design for Chronic and Diabetic Wound Treatment

Progress in biomaterial science and engineering and increasing knowledge in cell biology have enabled us to develop functional biomaterials providing appropriate biochemical and biophysical cues for tissue regeneration applications. Tissue regeneration is particularly important to treat chronic wounds of people with diabetes. Understanding and controlling the cellular microenvironment of the wound tissue are important to improve the wound healing process. In this study, we review different biochemical (e.g., growth factors, peptides, DNA, and RNA) and biophysical (e.g., topographical guidance, pressure, electrical stimulation, and pulsed electromagnetic field) cues providing a functional and instructive acellular matrix to heal diabetic chronic wounds. The biochemical and biophysical signals generally regulate cell-matrix interactions and cell behavior and function inducing the tissue regeneration for chronic wounds. Some technologies and devices have already been developed and used in the clinic employing biochemical and biophysical cues for wound healing applications. These technologies can be integrated with smart biomaterials to deliver therapeutic agents to the wound tissue in a precise and controllable manner. This review provides useful guidance in understanding molecular mechanisms and signals in the healing of diabetic chronic wounds and in designing instructive biomaterials to treat them.

Thermoresponsive polyurethane/siloxane membrane for wound dressing and cell sheet transplantation: In-vitro and in-vivo studies

Polyurethane/siloxane based wound dressing for transferring fibroblast cell sheet to wounded skin and ability to provide an optimum condition for cellular activity at damaged tissue was prepared in this research. The dressing was made thermoresponsive, via the introduction of a poly(N-isopropyl acrylamide) copolymer into the backbone of dressing. The ability of membrane for adhesion, growth, and proliferation of fibroblast cells was improved via surface modification with gelatin. The optimized dressing exhibited appropriate tensile strength (4.5MPa) and elongation at break (80%) to protect wound against physical forces. Due to controlled equilibrium water absorption of about 89% and water vapor transmission rate of 2040g/m(2)day, the dressing could maintain the favorable moist environment over moderate to high exuding wounds. The grown cell sheet on dressing membrane could easily roll up from the surface just with lowering the temperature. The in vivo study of the wound dressed with cell loaded membrane confirmed the accelerated healing and production of tissue with complete re-epithelization, enhanced vascularization, and increased collagen deposition on the damaged area.

Platelet-Rich Plasma-Loaded Poly(d,l-lactide)-Poly(ethylene glycol)-Poly(d,l-lactide) Hydrogel Dressing Promotes Full-Thickness Skin Wound Healing in a Rodent Model

Traditional therapeutic methods for skin wounds have many disadvantages, and new wound dressings that can facilitate the healing process are thus urgently needed. Platelet-rich plasma (PRP) contains multiple growth factors (GFs) and shows a significant capacity to heal soft tissue wounds. However, these GFs have a short half-life and deactivate rapidly; we therefore need a sustained delivery system to overcome this shortcoming. In this study, poly(d,l-lactide)-poly(ethylene glycol)-poly(d,l-lactide) (PDLLA-PEG-PDLLA: PLEL) hydrogel was successfully created as delivery vehicle for PRP GFs and was evaluated systematically. PLEL hydrogel was injectable at room temperature and exhibited a smart thermosensitive in situ gel-formation behavior at body temperature. In vitro cell culture showed PRP-loaded PLEL hydrogel (PRP/PLEL) had little cytotoxicity, and promoted EaHy926 proliferation, migration and tube formation; the factor release assay additionally indicated that PLEL realized the controlled release of PRP GFs for as long as 14 days. When employed to treat rodents’ full-thickness skin defects, PRP/PLEL showed a significantly better ability to raise the number of both newly formed and mature blood vessels compared to the control, PLEL and PRP groups. Furthermore, the PRP/PLEL-treated group displayed faster wound closure, better reepithelialization and collagen formation. Taken together, PRP/PLEL provides a promising strategy for promoting angiogenesis and skin wound healing, which extends the potential of this dressing for clinical application.

Wound dressings, does it matter and why?

Compression therapy and treating venous insufficiency is the standard of care for venous leg ulcers. The need for debridement on healing venous leg ulcers is still debated. Dressings are often used under compression bandages to promote faster healing and prevent adherence of the bandage to the ulcer. A wide range of dressings is available, including modern dressings with different kinds of biological activity. Microbial burden is believed to underlie delayed healing, but the exact role of microbiofilm in wound healing is uncertain. Before choosing a specific wound dressing, four main functions should be considered: (1) cleaning, (2) absorbing, (3) regulating or (4) the necessity of adding medication. There is no clear evidence to support the use of one dressing over another, as demonstrated by many Cochrane review studies. In addition, the prescriber should enquire about contact allergies that may also develop during wound treatment. It is shown that early intervention and early investment may reduce the cost of treatment. The choice of wound dressings should be guided by cost, ease of application and patient and physician preference and be part of the complete strategy. The role of the medical specialist is evident. Wound dressings matter as part of the optimal treatment in VLU patients.

Sulfated Seaweed Polysaccharides as Multifunctional Materials in Drug Delivery Applications

In the last decades, the discovery of metabolites from marine resources showing biological activity has increased significantly. Among marine resources, seaweed is a valuable source of structurally diverse bioactive compounds. The cell walls of marine algae are rich in sulfated polysaccharides, including carrageenan in red algae, ulvan in green algae and fucoidan in brown algae. Sulfated polysaccharides have been increasingly studied over the years in the pharmaceutical field, given their potential usefulness in applications such as the design of drug delivery systems. The purpose of this review is to discuss potential applications of these polymers in drug delivery systems, with a focus on carrageenan, ulvan and fucoidan. General information regarding structure, extraction process and physicochemical properties is presented, along with a brief reference to reported biological activities. For each material, specific applications under the scope of drug delivery are described, addressing in privileged manner particulate carriers, as well as hydrogels and beads. A final section approaches the application of sulfated polysaccharides in targeted drug delivery, focusing with particular interest the capacity for macrophage targeting.

Influence of hydrophilic polymers on functional properties and wound healing efficacy of hydrocolloid based wound dressings

The purpose of this study was to investigate the influence of different hydrophilic polymers on the swelling, bioadhesion and mechanical strength of hydrocolloid wound dressings (HCDs) in order to provide an appropriate composition for a hydrocolloid wound dressing system. In this study, the HCDs were prepared with styrene-isoprene-styrene copolymer (SIS) and polyisobutylene (PIB) as the base using a hot melting method. Additionally, numerous SIS/PIB-based HCDs were prepared with six hydrophilic polymers, and their wound dressing properties were assessed. Finally, the wound healing efficacy of the selected formulations was compared to a commercial wound dressing. The swelling ratio, bioadhesive force and mechanical strengths of HCDs were increased in the order of sodium alginate>sodium CMC=poloxamer=HPMC>PVA=PVP, sodium alginate>sodium CMC=poloxamer>PVA>HPMC=PVP and sodium alginate≥PVA>PVP=HPMC=sodium CMC>poloxamer, respectively. Among the hydrophilic polymers tested, sodium alginate most enhanced the swelling capacity, bioadhesive force and mechanical strengths. Thus, the hydrophilic polymers played great role in the swelling, bioadhesion and mechanical strength of SIS/PIB-based HCDs. The HCD formulation composed of PIB, SIS, liquid paraffin and sodium alginate at the weight ratio of 20/25/12/43 gave better wound dressing properties and more excellent wound healing efficacy than the commercial wound dressing. Therefore, the novel HCD formulation could be a promising hydrocolloid system for wound dressings.

Electrospinning of natural polymers for advanced wound care: towards responsive and adaptive dressings

Nanofibrous dressings produced by electrospinning proteins and polysaccharides are highly promising candidates in promoting wound healing and skin regeneration.

In vitro wound healing assays – state of the art

Wound healing is essential for the restoration of the barrier function of the skin. During this process, cells at the wound edges proliferate and migrate, leading to re-epithelialization of the wound surface. Wound healing assays are used to study the molecular mechanisms of wound repair, as well as in the investigation of potential therapeutics and treatments for improved healing. Numerous models of wound healing have been developed in recent years. In this review, we focus on in vitro assays, as they allow a fast, cost-efficient and ethical alternative to animal models. This paper gives a general overview of 2-dimensional (2D) cell monolayer assays by providing a description of injury methods, as well as an evaluation of each assay’s strengths and limitations. We include a section reviewing assays performed in 3-dimensional (3D) culture, which employ bioengineered skin models to capture complex wound healing mechanics like cell-matrix interactions and the interplay of different cell types in the healing process. Finally, we discuss in detail available software tools and algorithms for data analysis.

Evaluation of in vitro wound adhesion characteristics of composite film and wafer based dressings using texture analysis and FTIR spectroscopy: a chemometrics factor analysis approach

Comparing adhesion of film and wafer based dressings using texture analysis and FTIR spectroscopy combined with chemometrics target factor analysis.