Breakthroughs In Biodegradable Dressing Materials

Overview

We have all been advised not to pick a scab to prevent infection from happening, and for good reason: scabs play an important role in our skin’s natural healing process. While our skin can heal on its own when it comes to small wounds, larger injuries or deep ulcers require more than just a scab to protect them from infections. For these larger injuries, we need wound dressings, which are special materials that shield our body from infection whilst the body heals.¹

Whereas traditional wound dressings such as gauzes or bandages act as a physical barrier against the entry of infectious organisms, they do not do anything to actively help the body heal. This is where biodegradable dressings come in. This new type of dressing is a novel invention that is transforming the world of wound care in several ways.^1,2

A huge advantage is that biodegradable dressings are designed to naturally break down over time and return to the environment safely as nutrients.¹ These dressings reduce the waste that is produced by traditional wound dressings. Biodegradable dressings also offer benefits to patients by actively promoting wound healing, offering better protection against infection and making dressing changes more comfortable. Many different types of biodegradable dressing materials are suitable for different types of wounds, all of which hold the promise of improving both healthcare outcomes and environmental sustainability.^1,2

What are dressing materials? 

Wounds cause damage to our skin, an organ which has vital roles, like regulating our body temperature or acting as a barrier to infection and ultraviolet (UV) radiation.¹ The skin can usually repair itself when it comes to smaller injuries. Still, larger injuries, such as those caused by burns, accidents or ulcers due to an underlying condition like diabetes, require dressing material.^1,2 Dressing materials are used to protect a wound or injury, to prevent infection and to promote healing. 

Studies have shown that roughly 50% of patients admitted to hospitals have wounds, which makes dressing materials very important as they are essential for wound management.³ Dressing materials cover the wound, protecting it from further injury, increasing comfort for patients and allowing their skin to heal and reform. They also protect the wound from infection, which reduces the risk of serious complications, including amputation. As so many people suffer from wounds, there is a lot of research on developing dressing materials which can speed up the healing process, reduce the risk of complications, and improve patients’ overall well-being.^1,3

Limitations of traditional dressing materials 

Traditional dressing materials include materials such as gauze dressings (sterile fabric to cover the wound), bandages and cotton wool. Whilst conventional dressings are effective in protecting the wound from getting infected, they are limited in creating the ideal healing environment for injuries.⁴ To heal quickly and aesthetically, wounds need to be exposed to sufficient levels of oxygen and also need good moisture control. Traditional materials are often unable to provide these things.³ 

Another important property of wound dressings is their ability to absorb exudate, which is the fluid produced by some wounds. Some traditional dressing materials have great absorptive capacity, but this means that they can also dry out wounds.¹ These dressing materials also have to be regularly changed, causing pain and discomfort for the patient and disrupting the healing process, especially as these dressing materials are dry and can end up sticking to the wound.^1,5 Despite their limitations, traditional dressing materials are still widely used, especially for more minor injuries. 

However, the characteristics of a wound determine which dressing should be used, and for more major wounds, more modern and advanced dressing materials are required. Modern dressing materials offer additional benefits alongside protection from infection, such as moisture control, oxygen permeability, and antimicrobial properties. Some examples of materials include films (transparent film material), hydrogels (water-based gels), hydrocolloids (double-layered dressing), alginates (seaweed-derived dressings), and foam dressings.^1,4

Scientists are now going one step further and have developed modern biodegradable dressings, which build on current dressings to further improve wound management, while also being environmentally friendly.³

Biodegradable dressing materials

Biodegradable dressings are a type of dressing material that naturally breaks down over time and can be safely disposed of in the environment.¹ Many different materials are being used for the production of biodegradable dressing materials, with the dressing material being chosen based on the characteristics of the wound and the patient’s needs.⁵ 

Natural biodegradable dressing materials 

Natural biomaterials used for dressings are materials that are derived from biological sources, which allows them to work well with the human body without harmful side effects (biocompatible).¹ They are broken down naturally by the body’s enzymes (a type of protein that speeds up chemical reactions). Natural biomaterials also often have properties that promote wound healing, unlike traditional dressings. There are many different types of biomaterials, each having its own advantages and specific uses.^1,6 These include: 

• Silk: A protein used for its softness and its ability to attract and stick to cells, promoting wound healing. 
• Chitosan: A substance derived from chitin that is found in shellfish shells. It has antimicrobial properties and promotes wound healing. 
• Hyaluronic acid (HA): A natural substance found in the body that is used in dressings for its ability to retain moisture. 
• Alginate: A substance derived from seaweed and highly absorbent, so is useful for wounds that produce a lot of exudate (fluid). 
• Collagen: A protein found in the body that supports tissue repair. 
• Gelatin: A material derived from collagen and is used for its wound-healing properties. 
• Cellulose: A substance derived from plants which have high absorbability, and is used for exudate-producing wounds.^1,4,6,7

However, it should be stressed that the applications of these materials are often limited by their low physical strength and being degraded too quickly, which means they may be broken down before they can have their desired effect. Therefore, synthetic (man-made) biodegradable materials or composite biodegradable materials may be used to overcome these limitations.¹

Synthetic biodegradable materials 

Synthetic materials are man-made materials that are designed to overcome the limitations of natural biomaterials, as they are mechanically stronger and degrade less easily. They also still offer the benefits of natural biomaterials, such as being biocompatible, improving wound healing, and being versatile for different uses. Synthetic dressing materials can be designed to achieve specific properties and to serve as carriers for cells, growth factors, or drugs, which allows them to create the best environment for the wound healing process.^1,6 There are many different forms of these synthetic materials which can be used to make dressings, which are outlined below: 

However, these synthetic materials can also have disadvantages or limitations, which can be overcome by combining them with other materials, resulting in the development of composite biodegradable materials. 

Composite biodegradable materials 

Every natural or synthetic material has its own set of unique advantages and disadvantages that make it more suitable for different types of wounds. To overcome some of the disadvantages, we can produce composite materials, which are combinations of different biodegradable dressing materials. In this way, we can tailor dressings towards specific wounds. 

Many different composite materials have been designed, each with specific properties. Here are some examples of composite materials: 

• Silk and Polyvinyl Alcohol (PVA): when silk is combined with PVA, a very mechanically strong dressing material is produced, which can facilitate wound healing.⁶ 
• Alginate and Poly(lactic-co-glycolic Acid) (PLGA): whilst PLGA has great mechanical properties and can be used to deliver drugs, it cannot create a moist environment as it absorbs exudates in the process of healing. These properties are supplied by alginates, resulting in the development of a more advantageous dressing.¹

In addition, other materials can be added to improve dressing materials: 

• Silver (Ag) or Zinc Oxide (ZnO) nanoparticles: These are tiny particles that have antibacterial properties and can be applied to prevent infection and improve wound healing. ZnO nanoparticles can be combined with composite silk and PVA dressings.⁶ 
• Enzymes: Enzymes are a special type of protein that speed up chemical reactions. In chronic wounds, they can break down dying tissue to promote healing.³ 
• Growth factors: These can help tissues to regrow and promote wound healing at a higher rate when used in dressings.¹

Biodegradable dressing fabrication techniques

Alongside the materials that are used for wound dressings, the technique of producing the dressings can be tailored to the specific type of wound, and for specific applications. Various new techniques are being utilised to produce wound dressings: 

Electrospinning nanofibre-based dressing materials

These dressing materials are made by taking incredibly tiny fibres, much thinner than human hair, and spinning them together using electricity to create a dressing. Materials created using this technique have many advantages in wound healing, such as having a large surface area, which allows lots of oxygen to get to the wound whilst at the same time preventing bacteria from invading, therefore reducing the risk of infection. In addition, using biodegradable materials such as these fibres makes materials produced by this technique biocompatible and degradable so that they can be absorbed into the skin safely.^1,6

Hydrogel dressings

Hydrogels are a type of dressing that can hold large amounts of water, making them ideal for wounds that produce a lot of fluid. This ability also allows them to create a moist environment for healing and, therefore, preventing infection.¹ Recently, a new cellulose-based hydrogel dressing with added silver nanoparticles and curcumin, a component of turmeric, has been developed. These biodegradable dressings have been created to speed up the healing of chronic wounds, and the natural ingredients may even be able to reduce the risk or prevent amputation.⁸

Three-dimensional (3D) printing 

3D printing is a way of creating 3D objects by building them in a layer-by-layer manner. In wound management, 3D printing can be used to create custom dressing materials that suit the size and shape of each wound and the needs of each patient. This is done by initially scanning the wound and designing a dressing based on it before finally printing the dressing using biodegradable dressing materials.^1,4 

Benefits of biodegradable dressing materials 

Biodegradable dressing materials have many benefits, such as: 

• Reduced patient discomfort: these dressings prevent the pain patients have to experience due to dressing changes. They also require less maintenance, which enhances the patient's overall experience.  
• Ideal healing environment: materials like hydrogels can control moisture levels, which can help create the ideal healing environment. 
• Antimicrobial properties: some biodegradable dressing materials incorporate silver or zinc oxide (ZnO) nanoparticles, which have antimicrobial properties. 
• Customisable: composite materials that are specific to different types of wounds can be created. Biodegradable dressings can also be made to suit different wound shapes and sizes. 
• Biocompatible: biodegradable tissues are compatible with the body’s tissues and are less likely to cause an adverse reaction. 
• Reduced scarring: by creating the ideal healing environment and supporting natural tissue growth, they can improve the aesthetic outcome of the wound. 
• Environmentally sustainable: biodegradable dressings are absorbed by the body and don’t have to be changed, creating less waste, which is beneficial for the environment. 

Challenges and future directions 

Biodegradable dressings are helping to create more environmentally friendly and patient-suitable dressing alternatives for wounds and injuries. However, many of these modern dressings have only been used on a limited number of patients, and wound management is a complex process that is affected by many factors like wound type, wound size and the patient’s overall health. Due to these factors and the wide range of dressing options available, it can be difficult and also overwhelming for clinicians to choose the right dressing tailored to each patient’s needs. 

Scientists are continuously working towards creating new dressing materials and improving the ones we already have. This often involves using a mixture of different materials to combine their advantageous properties. Whilst this can create more diverse and advantageous dressings, in some cases, this can affect a dressing’s mechanical properties or its ability to absorb fluids. Therefore, more research is needed to find the perfect balance when blending materials. 

Whilst many new promising materials have been developed, they are still yet to be used clinically on a wide scale because of cost and complex production considerations. Therefore, research should also focus on simplifying the way that these materials are made and, therefore, reducing costs so that these dressing materials can be used on a larger scale.^1,5,6 

Summary 

Wound dressings are essential for protecting and managing injuries. While traditional dressing options such as gauzes and bandages offer basic protection of wounds, they do not actively assist in wound healing. This is where biodegradable dressings come in; their ability to promote wound healing, improve infection protection and enhance patient comfort in dressing changes whilst also being environmentally friendly is slowly revolutionising the world of wound care. 

Biodegradable dressing can be produced from natural biomaterials like silk or hyaluronic acid, synthetic biodegradable materials like PVA or PLA, or from a combination of both. Wound dressings are also produced using different techniques like 3D printing or hydrogel production. Each material and technique offers its own advantages, and dressings can be chosen based on specific wound characteristics and individual patients' needs. 

Biodegradable dressings have many advantages which can improve patient outcomes. However, whilst these advantages hold promise for the future of wound management, the challenges in selecting the right dressing for specific wounds, combining materials, production processes, and costs remain. In the future, we hope that through research, we can overcome these challenges and develop biodegradable dressing materials that can be available on a wide scale, improving outcomes for not just patients but for the environment, too.