Alginate in Wound Dressings

Development of rhamnose-rich hydrogels based on sulfated xylorhamno-uronic acid toward wound healing applications

An array of biological properties is demonstrated in the category of extracts broadly known as ulvans, including antibacterial, anti-inflammatory and anti-coagulant activities. However, the development of this category in biomedical applications is limited due to high structural variability across species and a lack of consistent and scalable sources. In addition, the modification and formulation of these molecules is still in its infancy with regard to progressing to product development. Here, a sulfated and rhamnose-rich, xylorhamno-uronic acid (XRU) extract from the cell wall of a controlled source of cultivated Australian ulvacean macroalgae resembles mammalian connective glycosaminoglycans. It is therefore a strong candidate for applications in wound healing and tissue regeneration. This study targets the development of polysaccharide modification for fabrication of 3D scaffolds for skin cell (fibroblast) culture. The XRU extract is methacrylated and UV-crosslinked to produce hydrogels with tuneable mechanical properties. The hydrogels demonstrate high cell viability and support cell proliferation over 14 days, which are far more functional than comparable alginate gels. Importantly, an XRU-based bioink is developed for extrusion printing 3D constructs both with and without cell encapsulation. These results highlight the close to product potential of this rhamnose-rich XRU extract as a promising biomaterial toward wound healing. Future studies should be focused on in-depth in vitro characterizations to examine the role of the material in dermal extracellular matrix (ECM) secretion of 3D printed structures, and in vivo characterizations to assess its capacity in supporting wound healing.

Antimicrobial Wound Dressings as Potential Materials for Skin Tissue Regeneration

The most important properties of performant wound dressings are biocompatibility, the ability to retain large amount of exudate and to avoid complications related with persistent infection which could lead to delayed wound healing. This research aimed to obtain and characterize a new type of antimicrobial dressings, based on zinc oxide/sodium alginate/polyvinyl alcohol (PVA). Zinc oxide nanostructures, obtained with different morphology and grain size by hydrothermal and polyol methods, are used as antimicrobial agents along with sodium alginate, which is used to improve the biocompatibility of the dressing. The nanofiber dressing was obtained through the electrospinning method. Characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the structural and morphological properties of the obtained powders and composite fibers. Their antimicrobial activity was tested against Gram negative Escherichia coli (E. coli), Gram positive Staphylococcus aureus (S. aureus) bacteria and Candida albicans (C. albicans) yeast strains. The in vitro biocompatibility of the obtained composites was tested on human diploid cells. The obtained results suggest that the composite fibers based on zinc oxide and alginate are suitable for antimicrobial protection, are not toxic and may be useful for skin tissue regeneration if applied as a dressing.

In situ synthesis of poly (γ- glutamic acid)/alginate/AgNP composite microspheres with antibacterial and hemostatic properties

In the present work, a poly(γ-glutamic acid)/alginate/silver nanoparticle (PGA/Alg/AgNP) composite microsphere with excellent antibacterial and hemostatic properties was prepared by the in situ UV reduction and emulsion internal gelation method, and its potential application for antibacterial hemostatic dressing was explored. Well dispersed AgNPs were in situ synthesized by a UV reduction method with alginate as stabilizer and reductant. The AgNPs showed excellent antibacterial activities against both gram-negative and gram-positive bacteria. Additionally, the AgNPs prepared by the in-situ UV reduction exhibited better biocompatibility and antibacterial effects than those prepared by the conventional chemical reduction method. PGA/Alg/AgNP composite microspheres were then prepared with the AgNPs by an emulsion internal gelation method. Such microspheres were found to be a porous and hollow network with pH-sensitive swelling properties and excellent hemostatic performance, indicating its application potentials as an advanced antibacterial hemostatic material.

A review on cellulose nanocrystals as promising biocompounds for the synthesis of nanocomposite hydrogels

Hydrogels are hydrophilic cross-linked polymer networks formed via the simple reaction of one or more monomers with the ability to retain a significant extent of water. Owing to an increased demand for environmentally friendly, biodegradable, and biocompatible products, cellulose nanocrystals (CNCs) with high hydrophilicity have emerged as a promising sustainable material for the formation of hydrogels. The cytocompatibility, swellability, and non-toxicity make CNC hydrogels of great interest in biomedical, biosensing, and wastewater treatment applications. There has been a considerable progress in the research of CNC hydrogels, as the number of scientific publications has exponentially increased (>600%) in the last five years. In this paper, recent progress in CNC hydrogels with particular emphasis on design, materials, and fabrication techniques to control hydrogel architecture, and advanced applications are discussed.

Effective Healing of Leprosy Chronic Plantar Ulcers by Application of Human Amniotic Membrane Stem Cell Secretome Gel

Background:

Chronic plantar ulcers are common problems for leprosy patients with numb feet due to their prolonged healing time. Chronic plantar ulcers affect the quality of life of patients and can lead to more serious complications, such as disability and deformity, if not handled appropriately. Wound-care products in the market, however, give unsatisfactory results. One factor in the delayed healing of chronic plantar ulcers due to leprosy is the lack of growth factors and cytokines in the wound due to reduced blood supply. We speculated that application of human amniotic membrane stem cell (hAMSC) secretome, which contains growth factors and cytokines, could improve wound healing.

Aim:

To evaluate the effect of topical application of a hAMSC secretome gel on wound healing of chronic plantar ulcers due to leprosy.

Materials and Methods:

We recruited 11 patients after leprosy treatment with chronic plantar ulcers due to leprosy. hAMSC secretome gel was applied topically to ulcers every 3 days for up to 2 months. Ulcer size and possible side effects or complications from gel application were evaluated weekly.

Results:

The ulcers of 8 of 11 patients (72.7%) completely healed, the ulcers of 2 patients (18.2%) partially healed, and the ulcers of 1 patient (9.1%) persisted. No ulcers became worse.

Conclusion:

hAMSC secretome was found to be an efficacious and well-tolerated alternative therapy for chronic plantar ulcers due to leprosy.

Recent Advances in Pharmaceutical Potential of Brown Algal Polysaccharides and their Derivatives

Marine plants, animals and microorganisms display steady growth in the ocean and are abundant carbohydrate resources. Specifically, natural polysaccharides obtained from brown algae have been drawing increasing attention owing to their great potential in pharmaceutical applications. This review describes the structural and biological features of brown algal polysaccharides, including alginates, fucoidans, and laminarins, and it highlights recently developed approaches used to obtain the oligo- and polysaccharides with defined structures. Functional modification of these polysaccharides promotes their advanced applications in biomedical materials for controlled release and targeted drug delivery, etc. Moreover, brown algal polysaccharides and their derivatives possess numerous biological activities with anticancer, anticoagulant, wound healing, and antiviral properties. In addition, we also discuss carbohydrate- based substrates from brown algae, which are currently in clinical and preclinical studies, as well as the marine drugs that are already on the market. The present review summarizes the recent development in carbohydratebased products from brown algae, with promising findings that could rapidly facilitate the future discovery of novel marine drugs.

Recent Advances in the Use of Algal Polysaccharides for Skin Wound Healing

BACKGROUND

Chronic skin wounds and pressure ulcers represent major health care problems in diabetic individuals, as well as patients who suffered a spinal cord injury. Current treatment methods are only partially effective and such wounds exhibit a high recurrence rate. Open wounds are at high risk of invasive wound infections, which can lead to amputation and further disability. An interdisciplinary approach is needed to develop new and more effective therapies.

METHODS

The purpose of this work is to review recent studies focusing on the use of algal polysaccharides in commercially available as well as experimental wound dressings. Studies that discuss wound dressings based on algal polysaccharides, some of which also contain growth factors and even living cells, were identified and included in this review.

RESULTS AND CONCLUSION

Algal polysaccharides possess mechanical and physical properties, along with excellent biocompatibility and biodegradability that make them suitable for a variety of applications as wound dressings. Furthermore, algal polysaccharides have been used for a dual purpose, namely as wound covering, but also as a vehicle for drug delivery to the wound site.

Healing kinetics of diabetic wounds controlled with charge-biased hydrogel dressings

This study investigates the properties and use as wound-dressings of hydrogels made of anionic 3-sulfopropyl methacrylate (SA) and cationic [2-(methacryloyloxy)ethyl]trimethylammonium (TMA) to form poly(SA-co-TMA) gels with varying charge bias.

Preparation Method of Porous Dressing Materials Based on Butyric-Acetic Chitin Co-Polyesters

A method for obtaining highly porous materials in the form of film, based on the butyric-acetic chitin co-polyesters, containing 90% of butyryl and 10% of acetyl groups, was developed. The highly porous films, with thickness up to 0.11 mm, were obtained by two methods: (a) pouring 5% BAC 90/10 solution in ethanol on the layer of solid salts (porophor agent) which after solidification was eluted with water; (b) application of the suspension of porophor agent in BAC 90/10 solution in the solvent mixture with density similar to bulk porophor agent. In the final stage, the materials were obtained with porosity up to 95⁻99% and tensile strength 5 cN, which can be used as an active layer of medical dressings. The optimised procedure was used in the production of porous medical dressings (Medisorb) on an industrial scale. In the industrial method, NaCl was used as a porophor agent in the solid form and as a 3% solution in polymer. The final materials were characterised by porosity and other functional parameters at the level recommended for medical dressings. Medisorb series materials do not show in vitro cytotoxic activity.

Biopolymers: Applications in wound healing and skin tissue engineering

Wound is a growing healthcare challenge affecting several million worldwide. Lifestyle disorders such as diabetes increases the risk of wound complications. Effective management of wound is often difficult due to the complexity in the healing process. Addition to the conventional wound care practices, the bioactive polymers are gaining increased importance in wound care. Biopolymers are naturally occurring biomolecules synthesized by microbes, plants and animals with highest degree of biocompatibility. The bioactive properties such as antimicrobial, immune-modulatory, cell proliferative and angiogenic of the polymers create a microenvironment favorable for the healing process. The versatile properties of the biopolymers such as cellulose, alginate, hyaluronic acid, collagen, chitosan etc have been exploited in the current wound care market. With the technological advances in material science, regenerative medicine, nanotechnology, and bioengineering; the functional and structural characteristics of biopolymers can be improved to suit the current wound care demands such as tissue repair, restoration of lost tissue integrity and scarless healing. In this review we highlight on the sources, mechanism of action and bioengineering approaches adapted for commercial exploitation.