Medical applications for superabsorbent polymers
Medical applications for superabsorbent polymers
In the medical areas, until around 1980, the commonly used absorbent materials were cellulose or fibre-based products used in either woven and simple nonwoven items, opened fibre formats such as absorbent cotton (cotton wool) and some fluff pulp (bleached kraft or thermomechanical) as seen in tissue. The water absorbent capacity of these types of materials is only in the region of 11 times their weight, but most of this is lost under low to moderate pressure.
The rising demand for medical products such as gauzes and bandages is projected to create huge opportunities
The development of superabsorbent technology and performance was largely led by demands in the disposable hygiene segment, which has led to new thinking in the medical sector. As described in another of my articles, advances in research into fluid management and composite design thinking have ultimately allowed the development of the ultra-thin baby diaper and aesthetically useful and practical adult incontinence and feminine care items, which use a fraction of the materials – particularly fluff pulp – that earlier disposable products consumed. Medical products have resulted as a follow-on from these advances.
The most prominent superabsorbent compounds are sodium polyacrylate and polyacrylamide copolymers. The former is commonly found in most absorbent hygiene products, while the latter is a synthetic flocculent that draws out certain colloids from whatever liquid it’s introduced to. Other polymeric materials used to make a superabsorbent polymer have included ethlyene maleic anhydride copolymer, cross-linked carboxymethylcellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile (PAN), to name a few. The last named, starch-grafted PAN is one of the oldest SAP forms created.
The use of superabsorbent fibre in the medical industry is mainly within advanced moist wound care products
Regarding the medical sector, there are a multitude of references to hydrogels. It needs to be noted that these are three-dimensional, hydrophilic, polymeric networks capable of absorbing large amounts of water or other related fluids. Due to their high water content, porosity and soft consistency, hydrogels closely simulate natural living tissue, more so than any other class of synthetic biomaterials.
Hydrogels may be chemically stable or they may degrade and eventually disintegrate and dissolve. These materials, while being extensively used and researched, notably in advanced wound care, fall out of the area of conventional superabsorbent technology and need to be considered in a separate article. The key herein this differentiation is spontaneity – hydrogels require time and often assistance to gel, whereas regular SAPs immediately tenaciously form gels on exposure to fluids.
The XStat by Revmedx works by injecting a group of small, rapidly-expanding sponges into a wound cavity
Enhanced fluid handling
SAPs in bandages, gauze and other dressing materials can mitigate higher levels of blood loss while remaining effective as doctors and nurses operate or attend to wounds in other ways.
Superabsorbency also reduces the amount of unconfined bodily fluids, curtailing the chances of disease transferral and even infection. A recent application has come in the form of army field dressings where a superabsorbent component in a dressing acts to literally ‘plug’ wounds on the battlefield, thus providing extra crucial life-saving time before more detailed medical treatment at field stations or the like. (1)
Superabsorbent dressings have an extra fluid-handling capacity. They are designed to be used on wounds of varying types that produce moderate to high volumes of wound fluid (known as exudate). In such cases, it has been shown for instance in a trial, that after only three days, dressing change frequency was reduced from once daily to twice weekly in 80% of patients. The superabsorbent dressing seemed to reduce complications associated with exudate production, stimulate wound healing and increase patient comfort; it may also save time and costs for caregivers. (2) If the wound has fluctuating volumes of exudate (i.e. low to high), or a heterogeneous healing process (mixed wound bed), a superabsorbent dressing with a built-in atraumatic surface contact layer may be more suitable. Moisture management is essential, both to maintain a moist wound healing environment and to protect the periwound skin from maceration.
Superabsorbents vary in the way they absorb and retain fluid and how they function under compression. Some superabsorbents can lock fluid inside the dressing. This fluid may contain bacteria and proteases, which can be harmful to the wound and surrounding skin (periwound area). (3) Due to their enhanced fluid-handling capacity and absorbency, superabsorbent dressings are designed for longer wear times and to reduce maceration. Superabsorbent dressings are suggested as being particularly useful for wound cleansing.
Superabsorbent dressings may have multiple layers, which can include a wound contact layer, an inner core containing fibres, powders, crystals or gelling agents to increase fluid absorption and retention properties, and some have a fluid repellent backing layer to prevent strikethrough. Some superabsorbent dressings absorb via osmosis, others through a capillary action while retaining a moist wound interface.
Non-adherent superabsorbent dressings require a secondary bandage, while others have adhesive borders to keep them in place.
Superabsorbent polymers are normally used in the AHP areas as a granular material. To provide less risks of SAP “leakage” into wounds, fibrous SAP formats based in some cases on modified polyacrylate processing or utilisation are now being commercially used in wound healing products. Although more costly than regular AHP SAPs, this increase can be accommodated by the pricing structures seen in wound care. (4)
Superabsorbents can be used on a variety of wounds, including:
- Pressure ulcers
• Venous ulcers
• Diabetic foot ulcers
• Arterial and neuropathic ulcers
• Postoperative wounds
• Traumatic wounds
• First and second degree burns (with caution)
• Oncology wounds (with caution)
• Donor sites
And more generally:
- Drug delivery (transdermal)
• Spill capture
• Dental pads
• Bed mats – disposable and washable
• Urine capture – bottles and bed-pans
Plastemart (5) reported 35% of the total amount of SAPs used in medicine in 2013 was specifically used in wound care.
Future looks bright
Global medical superabsorbent polymers market will grow at a CAGR of 7.5% between 2014 and 2020. The global medical superabsorbent polymers market was valued at US$96m in 2013 and, with the expected growth, it is expected to reach a valuation of US$192.2m by 2020, as per Transparency Market Research. The report states that the growth of global medical superabsorbent polymers market will be primarily due to the growing awareness about health and hygiene among the global population, and the increase in disposable incomes, especially in developing economies.
The rising demand for medical products such as wound dressings, surgical pads and bandages is projected to create a huge opportunity for the medical superabsorbent polymers market. In terms of product types, the report segments the medical superabsorbent polymers market into woven and nonwoven wound care products used to manufacture medical gauzes, sponges, healing patches, wound dressings and surgical tapes.
In 2013, nonwoven superabsorbent polymers accounted for a market share of over 70% in the global superabsorbent polymers market and the segment is expected to dominate the medical superabsorbent polymers market during the forecast period. In terms of applications, advanced wound care products are preferred over traditional wound care products because they are easier to handle and odour-free, and boost the healing process. Advanced wound care products accounted for over 35% of the medical superabsorbent polymers market in 2013. The demand for this segment is expected to grow consistently during the period from 2014 to 2020.
2. Faucher N et al Br J Nurs. 2012 Jun 28-Jul 11;21(12):S22, S24, S26-8.
3. Weigand C J Mater Sci Mater Med. 2011 Nov;22(11):2583-90. doi: 10.1007/s10856-011-4423-3. Epub 2011 Aug 26.
4. Technical Absorbents at techabsorbents.com