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Antimicrobial Protected Tubing 2010: Focus on New Materials

Fri, 04/30/2010 - 7:24am
Marcia Coulson

Several issues are pushing dramatic changes in the area of medical tubing. This article covers, in detail, what these areas are, what challenges they pose to all involved in making and using medical tubing, and what new approaches, materials and testing are going into the new breed of tubing that is being demanded by end users today.

Colorants can be added to the silver layer to differentiate antimicrobial tubes.
 Colorants can be added to the silver layer to differentiate antimicrobial tubes.

All medical material developers offer tailored solutions for improving polymer properties as well as working with chemical providers to create innovative antimicrobial solutions and additives. Finding the perfect blend between tubing materials and antimicrobial blends, coatings or linings is one of the keys to developing additional methods to reduce hospital acquired infections (HAIs) related to catheter and other invasive patient treatments involving tubing.

Unfortunately, catheter-related bloodstream infections are common in all intensive care units. Many result in patient death. If this weren’t bad enough, the bugs are getting stronger. Bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), also known as the “Superbug” are on the rise. Infection is also moving beyond invasive tubing use into the area of surgical implantation. This is causing device manufacturers to scramble for bacteria-fighting coatings and additives to incorporate into their products.

The fact that most medical insurance, including federally funded programs, now refuse to cover HAIs is making the use of antimicrobials a critical point for all medical care facilities.

As an antimicrobial technology for medical tubing and devices, silver ion compounds are still considered the most effective. While other technologies are under experiment, none have yet proven to provide the efficacy of silver. For silver ions to be used in antimicrobial technology, formulations must be combined with a carrier substance which is then incorporated into or onto, virtually any material at the time of manufacturing. These include plastics, silicones, rubber, and all of the newest polymer blends.

Released “on demand” from the carrier, silver ions actually attack bacteria cells with an action that chokes off the oxygen supply and prevents bacterial cells from multiplying. In laboratory testing, silver ion infusion has proven to be highly effective against not only bacteria but yeast, fungi, molds, and even the aggressive biofilms that can form around invasive tubing in the body and on all forms of surgical implants. Because silver is inorganic, it reduces the risk of adaptive “Superbugs”, which result from the overuse of antibiotics. Depending on the microorganism, silver ion antimicrobial technology has been shown to reduce microbial populations within minutes and maintain optimal performance for years.

Clear antimicrobials can be added to molded parts.
Clear antimicrobials can be added to molded parts.

Today, antimicrobial technology is moving away from PVC and silicone tubing materials. While low in cost, PVCs tend to have ecological disposal issues, and they also darken when antimicrobial coatings are applied to them. This does not affect the usefulness of the tubing, but almost all health care workers want to be able to see through tubing. Silicone materials have proven hard to work with in some tubing applications, and while not a major concern, there has been a potential for allergic reactions to silicon in some patients and medical workers. Due to these issues, material advancements are moving forward in the development of new polymers.

Companies such as Eldon James are at the forefront, working with material suppliers and third party antimicrobial development laboratories to provide better combinations of silver ion protection plus tubing material that address these issues. The most promising new materials are Thermoplastic Elastomers (TPEs).

TPE is a new RoHS compliant, recyclable, plastic material that combines the processing advantages of a thermoplastic with the properties and performance of a rubber-like material. It is a soft, flexible, highly elastic material that can be custom formulated to perform in a variety of processes, including injection molding, extrusion, blow molding, and thermoforming. Aside from basic tubing, TPE is the perfect partner for antimicrobial blends used in molded parts with complex geometries and extruded profiles. The material can easily be blended with other materials, including colorants. TPE materials are easy to work with, environmentally friendly, and remain clear when compounded with antimicrobial additives.

Technology in Action

On the purely developmental end, many companies are involved with specialty compounds created for specific end customers’ requirements. These companies form a bridge between the actual medical device manufacturer and the tubing manufacturer and take advantage of the latter to help them develop, refine and work out the kinks of new material/antimicrobial formulations before they take the product back to the medical device manufacturer. 

Clear antimicrobials allow clarity to see product flow.
Clear antimicrobials allow clarity to see product flow.

Using facilities such as Eldon James, they can test the manufacturability of new tubing and antimicrobial compounds. Custom material formulations for both the tubing and antimicrobial linings need to first be analyzed and tested for usefulness and compatibility, but then the actual determination of manufacturability of the products and true effectiveness of the antimicrobial solution must be processed within a commercial clean room manufacturing facility.

This is critical, because while there are many specialty antimicrobials and additives that may perform quite well in a laboratory environment, they simply cannot be manufactured on a large scale in a real-world situation cost-effectively, if at all. Some applications need fast acting antimicrobials and others need long lasting, while still others may need both simultaneously.

Several medical companies are working with Eldon James on customized tubing formulations using TPEs and antimicrobial silver. One advantage in using a silver based antimicrobial is that silver has not been shown to contribute to the development of resistant strains of microorganisms. In addition, silver based antimicrobials inhibit growth of some antibiotic resistant strains of bacteria due to their physical mode of action. This is highly prevalent in endotracheal tubing, which is used for patients who must rely on a ventilator to breathe for 24 hours or more. Patients requiring such a breathing support system are at risk of exposure to bacteria that can build up on the breathing tube or pass through the tube to their lungs, eventually causing a lung infection known as ventilator-associated pneumonia (VAP). Bacterial pneumonia is one of the most insidious hospital-acquired conditions.

The biggest market for silver ion antimicrobial tubing still remains in urology, where it is used for catheters, drainage tubes, drainage bags, and fluid collection systems. Urinary tract infections (UTI) are the most common HAIs today. To avoid these requires using tubing that incorporates antimicrobials. As mentioned previously, antimicrobials cloud PVC based tubing. Clinicians want a water-clear tube. TPE tubing solves this issue because it remains clear when it is co-extruded with an antimicrobial lining. Eldon James has introduced Flexelene silver TPE tubing that is rapidly growing use in this area. Its proven efficacy rate greatly reduces this most common type of HAI.

 

Beyond Tubing: Growth in Antimicrobial Markets

Taking antimicrobial protection to the next level, this technology is now being extended to the components that link tubing with medical devices and instrumentation. These components include luers and other types of medical connectors. Because IV assemblies are continually handled by nurses, hospital workers, and clinical staff, compounding the resins used in these connectors with silver ion materials inhibits growth of bacteria on contact surfaces, including the six pathogens known to cause catheter-related bloodstream infections. While it is certainly expected that all hospital and clinical devices are kept sterilized and clean, this simply adds a second layer of protection to help prevent the spread of pathogens.

This antimicrobial reduction coupler inhibits growth of bacteria on the inside and outside.
This antimicrobial reduction coupler inhibits growth of bacteria on the inside and outside.

Combinations of antimicrobials and new materials such as TPEs are enhancing the ability to meet both simple and complex medical tubing and component requirements. Customized antimicrobial/material blends are always ongoing to meet the needs of new applications.

Uses for antimicrobial/material blends are also currently moving beyond tubing and components. Research is being done using silver ion antimicrobial protection in a wide range of medical and pharmaceutical applications including textiles, paper, and even adhesives. With the growing trend toward self-medication for many chronic conditions, home drug delivery systems are also a new area. These must not only be precise and reliable, but benefit from microbial protection, whether disposable or reusable.

These are all areas for future growth in the antimicrobial medical market. While always considered for invasive tubing applications, antimicrobial materials are now seen as a key factor driving many areas of medical device and materials evolution.

Marcia Coulson is the President of Eldon James Corporation, and can be reached at 970-667-2728 or m.coulson@eldonjames.com.

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