Study on Using Hyaluronic Acid for Wound Dressings

The skin, as the body's first line of defence, plays a very important role in resisting the invasion of pathogens. However, in daily life, the skin is vulnerable to injury and wound formation. Wound healing is a complex and dynamic process that involves hemostasis, inflammation, proliferation and remodelling. The wound healing process can be prevented or delayed if the wound becomes infected or if other complications such as excessive inflammation occur. In addition, some burns and surgical wounds often result in scarring of the skin, also known as dermatofibrosis, which is detrimental to the normal function of the skin. Excessive scarring of skin tissue can lead to decreased flexibility, abnormal function, and even itching and pain. To overcome the limitations of the wound healing process, researchers have developed different biomaterials to produce wound dressings. Depending on their morphology, wound dressings can be classified as electrostatically spun silk, hydrogel, membrane or sponge. Despite the different forms, most of the wound dressings are non-toxic, antimicrobial, biocompatible and biodegradable, and have rapid wound healing properties [1].

Hyaluronic acid is an anionic mucopolysaccharide composed of D-glucuronic acid alternately linked with N-acetylaminoglucosamine, which is found in the extracellular matrix of vertebrates, skin, vitreous body of the eye, cartilage, and joint fluid. The physicochemical properties of hyaluronic acid include hydrophilicity, antioxidant properties, fluidity, and viscoelasticity. The biological functions of hyaluronic acid are related to its molecular weight, e.g., high molecular weight hyaluronic acid inhibits inflammation, anti-angiogenesis, and scarring, whereas low molecular weight hyaluronic acid promotes angiogenesis, inflammation, and scarring. Due to the limited role of endogenous hyaluronic acid, it is important to use exogenous hyaluronic acid to prepare different types of wound dressings for wound repair. The molecular structure of hyaluronic acid is shown in Figure 1.

1 Physicochemical properties of hyaluronic acid

Hyaluronic acid belongs to a group of glycosaminoglycans that, unlike other glycosaminoglycans, are not sulfated and are usually not covalently attached to any core protein. The unique physicochemical properties of hyaluronic acid, such as hydrophilicity, fluidity, viscoelasticity, and antioxidant properties, have led to its widespread use in the production of various forms of wound dressings.

1.1 Hydrophilicity

Hyaluronic acid is one of the important components of the extracellular matrix. Due to the presence of a large number of hydroxyl and carboxyl groups in its structure, hyaluronic acid is highly hydrophilic. This property also makes hyaluronic acid with a large number of negative charges, so as to attract more cations and water molecules. Hyaluronic acid has the properties of water absorption, water retention, etc., and also has a strong ability to complex water molecules, which is known as ‘nature's moisturising factor’, and can be used for eye lubrication, moisturising, and the treatment of dry eye.

1.2 Fluidising properties

Hyaluronic acid is also an important component of joint fluid, which can lubricate joints and reduce vibration, which is inseparable from its fluidity. In medical treatment, tracheal intubation is a key step in mechanical ventilation and respiratory support, and is used in cardiopulmonary resuscitation and respiratory diseases, etc. However, prolonged friction between the trachea and human tissues leads to damage of the mucous membrane of the laryngeal trachea, which results in inflammation, difficulty in articulation, and other symptoms, and in serious cases, it may endanger the lives of the patients. Clinical lubricants, including benzydamine hydrochloride gel, lidocaine 5% gel/cream, and corticosteroid creams, are commonly used to relieve these symptoms. The most commonly used lubricant is lidocaine cream, but it contains additives that can cause hypersensitivity reactions or trigger atopic dermatitis, so lubricating, non-toxic agents are constantly being investigated, and hyaluronic acid is a good candidate.

1.3 Visco-elasticity

At room temperature, hyaluronic acid is a white dry powdery solid with no odour, soluble in inorganic solvents and insoluble in organic solvents. When hyaluronic acid is dissolved in water, its aqueous solution has good viscoelasticity and permeability pressure, and also has non-Newtonian fluid properties. Since hyaluronic acid can be easily chemically modified, high molecular weight structures can be formed. Viscoelastic solutions of high molecular weight hyaluronic acid are well suited to mimic synovial fluid in joints, but do not have durable mechanical integrity [2].

1.4 Antioxidant properties

Hyaluronic acid also has antioxidant properties and can act as an antioxidant due to the formation of a viscous pericellular meshwork around the cell that limits the movement of ROS in the vicinity of the cell or other biomolecules, where excess reactive oxygen species can damage proteins, lipids, and DNA. Some of the antioxidant properties of hyaluronic acid are able to reduce the risk of apoptosis induced by UV light and the risk of acid-induced DNA damage.

2 Biological properties of hyaluronic acid

Studies have shown that the biological functions of hyaluronic acid (HA) are closely related to its molecular weight [3-4] . Hyaluronic acid can be classified into five categories according to its molecular weight (MW), i.e., HA oligosaccharides (O-HA, MW < 1×104 Da), which can promote angiogenesis, anti-tumour, wound healing, osteogenesis, immune and metabolic regulation, and ageing; and low-molecular-weight HA (LMW-HA, MW < 25×104 Da), which is more easily absorbed by the human body and can promote wound healing. Low molecular weight HA (LMW-HA, 1×104 Da < MW < 25×104 Da), more easily absorbed by the human body, can promote wound healing, vascularity, scarring, and plays an important role in chronic wound healing; medium molecular weight HA (MMW-HA, 25×104 Da < MW < 100×104 Da), moisturising, lubricating, and slow release of medicines, etc.; high molecular weight HA (HMW-HA, MW ≥ 1×106 Da), has good moisturising, lubricating, and adhesion properties. High molecular weight HA (HMW-HA, MW ≥ 1×106 Da) has good moisturising, lubrication, viscoelasticity, and can inhibit inflammation, anti-angiogenesis, and inhibit scarring; Ultra-high molecular weight HA (vHMW-HA, MW ＞ 6×106 Da) has lubrication, viscoelasticity, and so on.

2.1 Biodegradability

Hyaluronic acid is a kind of unsulfated glycosaminoglycan, which is the main component of the extracellular matrix of proliferating and migrating cells, and is especially abundant in early embryos. Exogenous hyaluronic acid can be degraded by physical (gamma radiation, ultrasound), chemical (acid hydrolysis, alkaline hydrolysis, oxygenation degradation), and enzymatic methods, and is commonly used in biomedical, cosmetic, and drug delivery applications. Endogenous hyaluronic acid is usually degraded by hyaluronidase and free radicals to low molecular weight hyaluronic acid and glucosamine.

2.2 Bacteriostatic properties

Comparison of the antimicrobial effect of hyaluronic acid with other natural polymers shows that chitosan is structurally similar to hyaluronic acid and has antimicrobial properties. Bacteria can avoid the inhibitory effect of hyaluronic acid in two ways, either when they contain the ability to produce hyaluronic acid as a mucus capsule, or when they can produce hyaluronan lytic enzymes to lyse it. Therefore, infections can occur in some hyaluronic acid applications, such as contact lenses and wound dressings. Low molecular weight hyaluronic acid has no inhibitory effect on Staphylococcus aureus, and high molecular weight hyaluronic acid has only a minimal inhibitory effect on Staphylococcus aureus.

2.3 Promoting wound healing

In the human body, hyaluronic acid binds to CD44, a receptor for keratinocytes in wounds, and stimulates cell proliferation and migration. The affinity of CD44 for hyaluronic acid is related to its molecular weight, i.e. the higher the molecular weight, the higher the affinity for the receptor.

3 Different forms of hyaluronic acid in wound dressings

The unique physicochemical and biological properties of hyaluronic acid have led to its use in a wide range of different forms of medical wound dressings such as electrostatically spun silk, membranes, hydrogels and sponges.

3.1 Hyaluronic acid based electrostatic spinning

Electrostatic spinning is an effective technique for the production of charged polymer filaments with diameters ranging from the micron to the nanometer scale under an electrostatic field. Fibre wound dressings prepared by ESP have high porosity, excellent ductility and good drug-carrying capacity, which not only allow wound cells to breathe, but also inhibit bacterial growth. Electrostatic spunlace dressings can also cover areas that are difficult to be covered by conventional dressings. These excellent properties have led to the use of electrostatic spinning technology in a wide range of biomedical applications.

Su Sena et al. [5] extracted hyaluronic acid and keratin from animals and loaded them as bioactive agents into coaxial electrospun fibre structures for wound treatment, and Sun Juan-feng et al. [6] successfully prepared electrospun nanofibres from a composite cohesive solution of chitosan and hyaluronic acid.

Abbas Zakeri Bazmandeh et al [7] prepared hyaluronic acid crosslinked chitosan and gelatin electrostatically spun membrane (Cs-Gel-HA) by electrostatic spinning, and the results showed that the Cs-Gel-HA membrane is more suitable for cell adhesion and can better promote skin regeneration. Hyaluronic acid is soluble in water, but its ionic nature leads to long-range electrostatic interactions, and the presence of counterions leads to a dramatic increase in the viscosity of the aqueous solution of hyaluronic acid but does not ensure sufficient chain entanglement for stable and efficient electrospinning.Morgane Séon-Lutz et al. [8] prepared insoluble hyaluronan-based nanofibres in pure water by using an electrostatic spinning technique. Polyvinyl alcohol (PVA) was added as a carrier polymer and the addition of hydroxypropylcyclodextrin (HPBCD) was found to promote the effective formation of nanofibre scaffolds and to make the electrostatic spinning process more stable.Yasmein Hussein et al [9] prepared enhanced polyvinyl alcohol/hyaluronic acid nanofibres using cellulose nanocrystallites (CNCs) as nanofillers and L-arginine as a wound healing promoter. Polyvinyl alcohol/hyaluronic acid nanofibres (PVA/HA-NFs) were prepared. The results showed that the PVA/HA/CNC/L-arginine NFs had good haemocompatibility, high protein adsorption, proliferation and adhesion ability.

3.2 Hyaluronic acid-based membrane

Membrane is a soft and flexible material. Yin Chuan-Jin et al [10] covalently attached hyaluronic acid (HA) to the surface of bovine serum albumin/silver (BSA/Ag) porous membranes to prepare BSA/Ag/HA films, which can be used as contact lenses, and showed good clarity, high water content, haematocompatibility, non-cytotoxicity, and antimicrobial properties. Josef Chmelař et al [11] used a solution flow-through method to produce water-insoluble freestanding films of lauroyl-modified hyaluronic acid as a novel biomaterial, which were homogeneous in texture, mechanically strong, and pliable.Abou-Okeil et al [12] prepared hyaluronic acid/sodium alginate films for use as a topical bioactive wound dressing.Rocha Neto J.B.B. [13] used BSA/Ag/HA films as contact lenses. Rocha Neto J.B.M et al [13] also developed hyaluronic acid (HA)/chitosan (Chi) based films and showed that platelet adhesion was significantly reduced in the sulphated modified functional films, providing new insights into the development of novel antithrombotic biomaterials.Fernanda Zamboni et al [14] used the cross-linking agent, bis- (β-ethyl isocyanate) disulphide (BIED), as a cross-linker. Fernanda Zamboni et al [14] used the cross-linker bis-(β-ethyl isocyanate) disulfide (BIED) to heterogeneously cross-link HA and then doped it with carbon nanofibres to optimise the mechanical and antimicrobial properties of the resulting film, which showed excellent mechanical and antimicrobial properties of the film-type wound dressing.

3.3 Hyaluronic acid-based hydrogels

Hydrogel dressing is a kind of wet dressing with high water content, which is soft and slightly elastic. Burns are one of the most devastating injuries, and despite modern treatments, patients still face many complications and post-burn scarring. In this regard, Dong Yi-Xiao et al [15] designed a hyaluronic acid-based stem cell delivery platform for rapid in situ gelation on wound contact, which enhances neovascularisation at the wound site and promotes burn wound healing and reduces scarring.16 Zhang Shao-Han et al [16] introduced a novel antioxidant material, arginine derivatives (AD), into dopamine-functionalised hyaluronic acid (HA), which has been shown to be a good choice for the treatment of burns. Zhang Shao-Han et al. [16] introduced a novel antioxidant material, arginine derivative (AD), into dopamine-functionalized hyaluronic acid (HA-DA) to prepare a new hydrogel with antioxidant activity. The scavenging rate of DPPH and -OH radicals was higher than that of HA-DA hydrogel. In addition, the hydrogel provided better cellular protection against external oxidative stress (reduced ROS and MDA levels, increased SOD and GPx enzyme activities) and better wound healing (enhanced VEGF and CD31 expression, enhanced tissue remodelling).

Inspired by the spontaneous clogging of blood cells during haemostasis, Liu Yi-Hao et al. [17] prepared a 5'-adenosine diphosphate-modified haemagglutinating hyaluronic acid (HA-ADP) hydrogel by physically cross-linking and freeze-drying, and the prepared hydrogel could promote the adhesion of platelets and erythrocytes and could induce significant procoagulant ability by activating platelets, which could complete hemostasis in vitro in a relatively short period of time. The hydrogel can promote the adhesion of blood platelets and erythrocytes. In addition, materials with antioxidant properties have attracted much attention in wound healing.

3.4 Hyaluronic acid-based sponges

Sponge dressings are highly porous materials that allow gas exchange between cells in the wound to accelerate wound healing and have good water absorption to keep the wound moist. However, ordinary sponge dressings have weak mechanical strength and need to be cross-linked with other polymers to fully utilise their characteristics.

Meng Xin et al [18] prepared a chitosan/alginate/hyaluronic acid composite sponge crosslinked with genipin, which has high mechanical strength, good biocompatibility and accelerated blood coagulation.Sanda-Maria Bucatariu et al [19] obtained a new type of sponge dressing by solvent-free thermal cross-linking of hyaluronic acid and poly(vinylmethyl ether-alt-maleic acid). Sanda-Maria Bucatariu et al. [19] obtained a novel sponge hydrogel (HA3P50) by solvent-free thermal cross-linking of hyaluronic acid and poly (methyl vinyl ether -alt-maleic acid), which is a biocompatible material to support the growth of tumour cells and provides a 3D platform to mimic tumour function for screening of anti-tumour drugs.20 Mathie Najberg et al. [20] prepared aerogel sponges with filipin, hyaluronic acid and heparin for soft tissue engineering. The aerogel sponge has high expansion, high porosity, high connectivity and soft texture close to the brain.

Rania Abdel-Basset Sanad et al [21] successfully prepared chitosan-hyaluronic acid/andrographolide nanocomposite scaffolds for wound healing and Annapoorna Mohandas et al [22] prepared composite sponge dressings made of chitosan and hyaluronic acid and loaded with vascular endothelial growth factor (VEGF). The results showed that the sponge dressing has the potential to induce angiogenesis in wound healing. Effective haemostasis is particularly important in the treatment of wounds, and Liu Jia-Ying et al [23] used a simple self-foaming method to produce a polysaccharide-based haemostatic porous sponge composed of hyaluronic acid and cationised dextran, which showed excellent in vivo haemostatic properties in a mouse model of hepatic haemorrhage.

4 Conclusion and Outlook

Hyaluronic acid stands out as one of the most attractive biomaterials among many others due to its excellent physicochemical and biological properties. Due to its high molecular weight and excellent water absorption capacity, it contributes to the maintenance of mechanical integrity, homeostasis, viscoelasticity and lubricity of tissues. In addition, it actively participates in important biological processes such as cell adhesion, migration, proliferation, differentiation and angiogenesis, and plays a crucial role in inflammation regulation, wound healing, tissue repair, morphogenesis, tumour proliferation and metastasis.

The excellent biodegradability and biocompatibility of hyaluronic acid-based biomaterials have also contributed to their wide application in the biomedical field. The use of hyaluronic acid and its substrates is increasing with the growing demand for products. For this reason, researchers in different countries have developed new smart dressings with different efficacies using hyaluronic acid as a base material. This article systematically describes the use of hyaluronic acid in different types of wound dressings, such as electrostatic spinning, membranes, hydrogels, sponges, etc., with the aim of providing ideas for the development of new biomaterials. In the future, hyaluronic acid-based wound dressings will be of great value in clinical wound repair.

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