Textile Solutions Medical Devices FOR

Medical Textiles are an Emerging Interdisciplinary Field in which Conventional Textile Technologies are Combining with Other Scientific Fields

By Geoff Fisher, European Editor, IFJ

niversities and research institutes in Europe are among the world leaders in developing medical textiles – fiberbased materials used in healthcare applications such as prevention, care and hygiene. These include dressings, prostheses, surgical sutures, healthcare apparel and barrier fabrics, as well as hygiene applications such as diapers, menstrual pads and surgical wipes.

As implantable medical devices, medical textiles have many diverse applications. They can be used as flexible scaffolds or structures for tissue in-growth and implant integration, conduits or barriers for blood flow, and as a means to join materials and secure implants in the body.

They are also used for tissue reinforcement and wound support, joint support and retrieving blood clots or preventing or reducing plaque debris in neurovascular applications.

Recent research in Europe demonstrates how medical textiles are an emerging interdisciplinary field in which con- ventional textile technologies, such as weaving, knitting, braiding and embroidery, are combining with other scientific fields, such as chemistry, medical and biomedical technology, pharmaceuticals and electrical engineering.

Dressing Reveals Early Signs of Infection

A nanocellulose wound dressing that can reveal early signs of infection without interfering with the healing process has been developed by Swedish researchers at Linköping University, in collaboration with colleagues from Örebro and Luleå Universities.

The dressing is made of tight mesh nanocellulose, which provides a barrier to bacteria and other microbes. At the same time, the material lets gases and liquid through, which is important for wound healing. Once applied, the dressing is designed to stay on during the entire healing process. Should the wound become infected, the dressing will show a color shift. Non-infected wounds have a pH of about 5.5. When an infection occurs, the wound becomes increasingly alkaline and may have a pH of 8 or higher, as bacteria in the wound change their surroundings to fit their optimal growth environment. An elevated pH in the wound can be detected long before any pus, soreness or redness, which are the most common signs of infection.

To make the wound dressing show the elevated pH, the researchers used bromthymol blue (BTB), a dye that changes color from yellow to blue when the pH exceeds 7. For BTB to be used in the dressing without being compromised, it was loaded onto a silica material with pores only a few nanometers in size. The silica material could then be combined with the dressing material without compromising the nanocellulose. The result is a wound dressing that turns blue when there is an infection.

Wound infections are often treated with antibiotics that spread throughout the body. But if the infection is detected at an early stage, local treatment of the wound may suffice, so the researchers are also developing antimicrobial substances based on lipopeptides that kill all types of bacteria.

Alternative to Antibiotics

Also in Sweden, research has been conducted at the University of Borås, to develop more resource-efficient methods for producing functional textiles using digital ink-jet printing.

The doctoral thesis of Ph.D. student Tuser Biswas involved fabrics printed with enzymes, which could be used in medical textiles with antimicrobial properties or to measure biological or chemical reactions. While developing a good enzyme ink was not easy, he was able to show how a printed enzyme could bind another enzyme to the surface of a fabric.

Although the activity of the enzymes decreased by 20–30% after printing, the results are still promising for future applications. The work has also provided new knowledge on many fundamental questions about printing biomaterials on fabric.

Biswas hopes that continued research in textile technology can provide alternatives to the use of antibiotics, which has resulted in increasing antibiotic resistance worldwide.

“Instead of treating the patient with a course of antibiotics, one can act preventively and more effectively by damaging the bacteria on the surface where they start to grow,” he said.

“In a wound dressing, for example, nanoparticle-based antimicrobials can reduce growth effectively. It is possible as nanoparticles can interact better with the bacterial membrane and reach the target more easily than conventional antimicrobials.”

Textile Center of Excellence

Last year, Stockholm, Sweden-based SHL Healthcare established a textile center of excellence in Borås to extend and streamline support for early project phases in collaboration with customers.

The facility is strategically situated inside the Textile Fashion Center and adjacent to a cluster of industry organizations such as Science Park Borås, Smart Textile, the Swedish School of Textiles and the University of Borås.

This will allow SHL Healthcare to easily access technology, engineering and textile materials that can optimize product innovations and sustainability.

Stent for Treating Hollow Organ Tumors

In Germany, researchers at RWTH Aachen University have developed a novel technology for the treatment of hollow organ tumors, which achieved second place in the RWTH Innovation Award.

A hollow organ tumor is responsible for one in four deaths from cancer and can- not usually be removed surgically. It is only possible to open the hollow organ for a short time using a stent. However, the tumor can grow back and penetrate the hollow organ through the stent.

The technology, developed by Dr. Ioana Slabu from the Institute of Applied Medical Technology and Benedict Bauer from the Institut für Textiltechnik at RWTH Aachen University, involves a polymer stent that has magnetic nanoparticles embedded in its fibers.

When electromagnetic fields are applied, the nanoparticles provide a controlled heating of the stent material and thus of the tumor. Because the tumor reacts more sensitively to heat than healthy tissue, it is destroyed, and the hollow organ remains open.

According to the researchers, the stent can be used to treat tumors in various hollow organs, such as in the bile duct or the esophagus, and also has the potential to treat tumors in other parts of the body, such as the prostate, stomach, intestine or bladder, or for cardiovascular diseases.

Silk for Repair of Injured Nerves

The treatment of nerve injuries with the aid of nerve guidance conduits has led to the desired regenerative success in some, but by no means all, cases. Now, a research team from the Medical University of Vienna (MedUni Vienna), Austria, and the UK’s University of Oxford has used silk as a promising material for repairing severed nerves.

In their experiments with silk from silkworms and spiders, the scientists also gained new insights into the effects of silk on neuronal healing processes, which could significantly advance therapeutic options in peripheral nerve reconstruction.

In the search for improved therapeutic options for nerve injuries, the team led by Professor Christine Radtke, head of MedUni Vienna’s Department of Plastic, Reconstructive and Aesthetic Surgery, in collaboration with researchers from Oxford, produced nerve conduits from two different types of silk: silk from silkworms was used for the tubes, while silk from spiders was used to fill them.

The function of these conduits was investigated in an animal model. Their experiments showed that the severed nerves adapted to the novel silk nerve guidance conduits and grew along the silk threads over the defect distance until the severed nerve endings were successfully reconnected.

Bioresorbable Membrane for Healing Wounds

Researchers at the Fraunhofer Institute for Silicate Research ISC and the Fraunhofer Institute for Toxicology and Experimental Medicine ITEM in Germany have developed a bioresorbable membrane for the treatment of both large external and internal wounds. The membrane is said to support wound healing and biodegrades completely in the body to a natural substance.

The novel membrane is based on a fiber fleece developed at Fraunhofer ISC, which has been approved as a medical device to support the regeneration of chronic wounds such as diabetic foot ulcers. During the healing process, the material dissolves completely within six to eight weeks.

Using an electrospinning method, the researchers have now managed to reduce the 50-µm fiber diameter by a factor of more than 50, resulting in fibers with diameters of less than 1 µm, which has made it possible to spin a Renacer silica gel sol into an open-meshed silica gel membrane consisting of fibers with a diameter of about 1 µm (in some cases, the diameters achieved were as small as 100 nm).

Using a confocal microscope, it was shown that the small-meshed membrane exhibits a barrier function, which prevents the passage of connective tissue cells for a period of at least seven days without interfering with cell proliferation. In addition, the membrane is resorbable, is not cytotoxic or genotoxic, and thus causes no direct damage to tissue or DNA. In addition, drugs can be encapsulated into the matrix of the silica gel fibers to be released during material resorption.

At Fraunhofer ISC, the GlioGel project is testing whether the Renacer material platform can be used as a depot for active substances in the treatment of brain tumors.

Chronic Wound Healing Using Glass Fibers

Researchers at the UK’s University of Birmingham have demonstrated that silver retains antimicrobial activity longer when impregnated into bioactive glass, and they have shown how this combination can deliver more long-lasting antimicrobial wound protection than conventional alternatives.

Bioactive glasses are a unique class of synthetic biomaterials made from silicone and have been used for many years in bone grafting.

Meanwhile, silver has long been known to prevent or reduce the growth of biofilms (communities of bacteria) in open wounds, and silver-based treatments are increasingly popular as they are effective against many antibiotic-resistant strains of bacteria.

These antimicrobial properties depend on silver remaining in an ionic form so it can penetrate bacterial cell walls and disrupt their life cycle. However, the silver ions or nanoparticles in wound dressings are prone to transforming to silver sulfide or silver chloride, which can reduce antimicrobial activity and hinder the success of treatment.

The researchers investigated the effects of bioactive glass doped with ionic silver on biofilms formed by Pseudomonas aeruginosa, a multi-drug resistant bacterium that easily forms biofilms and is a common cause of infection in chronic wounds.

The study showed that specific preparation, storage and application techniques can minimize the transformation of silver ions to silver chloride and so retain antimicrobial activity.

Single-Stranded Suture Threads

Women at risk of pregnancy loss who need a specialist surgical procedure could benefit from a single-stranded suture thread to reduce the risk of infection, according to results from the C-STICH clinical trial conducted by the University of Birmingham.

The trial involved more than 2,000 expectant mothers in the UK who needed a cerclage, a procedure in which a purse string suture is placed around the cervix during their pregnancy. Women were randomly allocated to have the surgical procedure performed using either a singlestranded thread or a braided thread.

The researchers evaluated whether there would be any difference in miscarriage or stillbirth, owing to an increased risk of infection, from using a braided suture thread. The team found that the mothers treated with single-stranded threads had no differences in pregnancy loss or preterm birth and reported fewer instances of infection and sepsis.

Dr. Vicky Hodgetts-Morton, National Institute for Health and Care Research clinical lecturer in obstetrics at the University of Birmingham and Birmingham Women’s Hospital, said: “The C-STICH trial results did show an increased risk of infections in labor and around the time of delivery with braided threads and this supported our hypothesis that a singlestranded thread could reduce the risk of infection developing during the pregnancy.”

However, the study also highlighted that while single-stranded suture threads led to better outcomes around infection, clinicians mentioned that such sutures were subjectively more difficult to remove and more often required surgery to help remove them under a general anesthetic.

Geoff Fisher is the European editor of International Fiber Journal, editor of Medical Textiles and a director of UK-based Textile Media Services, a B2B publisher of news and market reports on transport textiles, medical textiles, smart materials and emerging markets. He has more than 35 years of experience covering fibers and technical textiles. He can be contacted at gfisher@ textilemedia.com or +44 1603 308158.