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Real solutions

December 1st, 2014 / By: , / Technical

Medical and biomedical textile breakthroughs were presented
at IFAI Advanced Textiles Expo.

It might be a process that starts at the fiber level or one that uses a material in a new way, but there is no question that textiles are playing an important role in the treatment of many types of medical conditions. New research presented at IFAI Advanced Textiles Expo in October indicates that this area of the textiles market is poised for new growth.

Nanofiber mats

Dr. Laura Frasier of SNS NanoFiber Technology presented a discussion of new nonwoven nanofiber mats that could be used for skin decontamination, hemostats, wound dressings, cell culture devices and tissue engineering scaffolds. In tests for skin decontamination, for example, washing with soap and water was compared to using the mats to remove sunscreen from the skin. The soap and water method actually caused the sunscreen to go deeper into the hair follicles in the skin, but the mats almost completely removed it.

Using the mats for wound dressing and hemostats is especially advantageous because the material doesn’t have to be removed. Typically, removing dressings can cause a wound to open and bleed again.

The mats are self-supporting and so require no substrate, and they can be used to make composite materials with many layers, “sandwiching” other materials between the layers. Using an entrapment method (wrapping or entangling in the nanofibers) can produce a mat with super-absorbency. Encapsulating particles in the nanofiber can create a controlled-release application for drugs.

Additional applications in pharmaceutical cosmetics have also been explored.

Quad-axial, narrow, woven

Narrow woven fabrics have been used in a variety of medical devices, including for arteries, stents and AAA grafts; endovascular and endoluminal devices; orthopedic applications; artificial limbs; reduction of atrial septal defects (ASDs); bandaging and splints and blood filtration.

In a presentation by Louis Franconi, Bally Ribbon Mills, Bally, Pa., titled, “Fibers, 3-D Structures and Quad Axial Isotropic Woven Medical Devices,” Franconi showed how the company’s quad-axial isotropic woven narrow fabrics can provide advantages, particularly in strength and flexibility, in medical devices.

3-D refers to weaving materials in three dimensions (length, depth and height); Quad-axial weaving is weaving is in four directions, and quad-axial isotropic refers to weaving in 0, 90 and +/- 45 (or bias) degree direction. Typical looms are set to weave in the 0 (warp) and 90 (weft) directions. The benefit is that, rather than having to weave materials in layers and then joining them top to bottom with “Z” fibers, thus creating a thicker, layered structure in several ply’s (like plywood) which can delaminate or fall apart, materials can be woven in four directions (0.90 +/- 45 [bias] degree) in a single plane.  This makes for a thinner, stronger fabric that is better able to stand up in the application.Â

Medical devices are generally quite small, having a thinner profile (think compressing a fabric to fit into a catheter, thus allowing it to be delivered less invasively). Quad-axial woven materials should move the dynamic to where small materials can be produced with very high strength.

Implantable drug delivery

Extruded fibers, loaded with precise dosages of drugs can be made into various implantable drug delivery platforms that can provide healing with more precision and efficacy than other methods now used. This is the premise of Dallas, Texas-based TissueGen Inc., the developer of the absorbable polymer technology. The company’s CSO Dr. Kevin Nelson explained the breakthrough technology and its commercial viability in his presentation.

According to Nelson, the patented process enables fiber extrusion at room temperature with drugs and therapeutic agents previously impossible to incorporate in implant devices. Additional advantages of drug delivery from fiber are that the fibers are mechanically strong, remain in place, and offer uniform diameter and drug concentration, and slower release than spheres of the same diameter. Further, the devices can be readily mass-produced.

Of the fiber manufacturing methods—melt extrusion, electro-spinning and wet extrusion—the latter offers the strongest fibers and the widest range of drugs that can be used. However, this method uses harsh organic solvents, and very few drugs can survive them, so the company developed a process that creates a protective “bubble” for the drug in the solvent bath, the drug-loaded polymer is then extruded and a post process removes residual solvents.

Pharmaceuticals and biologically-derived agents can be loaded using this process. This includes antibiotics, antimicrobials and cancer remediation pharmaceuticals, as well as a variety of proteins and DNA agents.

Using a variable pitched coil delivery format, the process can direct cells to migrate through specified pathways and provide for a “tunable,” controlled drug delivery. For example, in a in vivo animal study, a monofilament fiber was loaded with Aldose Reductase Inhibitor (ARI), which blocks conversion of glucose to sorbitol, a potential cause of blindness in diabetic patients. A single dose over six months resulted in a five-fold reduction of diabetic state indicators in diabetic rats.

The company expects this drug delivery material will assist with nerve regeneration, tissue engineering, and in medical textiles for hernia mesh, pouches and slings, and tendon and ligament repair. A biodegradable drug-loaded (BDL) fiber trademarked ELUTE® is commercially available for pharmaceuticals and BDAs.

Nanowebs go green

“Green” electrospun nanowebs maintain breathability after heat crosslinking. That was the message Seshadri Ramkumar delivered while standing in for Uday Turaga’s presentation at Advanced Textiles Expo. As part of an education program featuring functional and nano technologies for industrial fabrics, Ramkumar presented the results of their research, titled “Breathable Standalone Poly (vinyl alcohol) Nanowebs.”

Can electrospun webs be created without organic solvents and without losing breathability or strength? The research presented by Ramkumar asked this question and the results presented indicated clearly that the answer is “yes.” By developing a homopolymer electrospun poly (vinyl alcohol) (PVA) nanoweb, the research team from Texas Tech University was able to evaluate the breathability, porosity and tensile strength of both treated and untreated nanowebs. Not only was there no significant effect of heat crosslinking on breathability, but the size of the pores in the nanowebs increased, allowing greater porosity of the substrate. The tensile strength of the nanowebs also increased slightly after the heat treatment.

By using a biodegradable solvent for the starting fiber, the team was able to create the webs using an eco-friendly electro-spinning process. Most nanofiber webs are spun with organic solvents. By using a doping solution of 12 percent PVA, a hydrophilic polymer, for the electro-spinning, the nanowebs were created without the use of organic solvents.

Breathability of nanowebs enables their use in a number of next-to-skin applications and is vitally important in medical, hygienic and smart textile applications, such as wound bandages and protective clothing liners. The increased porosity in the nanowebs is pivotal when using the scaffolds for cell and tissue culture, Ramkumar said.

What the future could hold

Chris Glasby of Secant Medical Inc. presented on “Existing Textile Technology Matched with Material Innovation,” addressing the use of advanced biomaterials and the engineering challenges faced when matched with current textile processes. Glasby pointed out that most surgery today is technology from the 1970s and 1980s, because the process to research, develop, test and get new technologies approved is a long one.

However, the goal for the future is regenerative medicine, which deals with replacing, engineering or regenerating human cells, tissues or organs. The company has developed a platform named Regenerez®, a bio-elastomer that Glasby called “the next disruptive technology.” He stressed that companies need to collaborate to move forward. “It’s all about synergies. We all work with each other,” he said. “The textile industry is just evolving. We have a bright future ahead.”

Janet Preus is senior editor, Advanced Textiles Source. Alisha Seifert is senior production editor at IFAI.

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