Medical science has made great strides in advancing the care and treatment of people around the globe. Thermoplastic and elastomeric materials have been an essential part in making different medical procedures and solutions safer and more cost effective. From test fit sockets to peristaltic pumps and centrifuges, there are few aspects of medical science today that do not benefit from the use of high-performance reservoir seals, medical-grade tubing, and LSR (liquid silicone rubber) technology.

Fig. 1 – CONMED’s surgical handpieces benefit from seals and gaskets that resist moisture intrusion.
Medical device manufacturers can benefit from engineering expertise, particularly with next-generation pumps, to alleviate potential issues attributed to seals. This especially relates to the areas of drug-delivery and pre-filled syringes. For instance, Trelleborg Sealing Solutions worked with CONMED Corporation, a medical device manufacturer, to solve their issues due to premature seal failure causing instrument downtime. Using an integrated spring-energized seal with a custom-shaped energizer and custom ultra-high molecular weight polyethylene (UHMWPE) jacket, Trelleborg’s engineering team developed a solution that reduced downtime from 28 percent to less than 1 percent for typical applications where a day of downtime can cost between $50,000 and $100,000. (See Figure 1)

The customized solution not only enabled the syringe to keep running even when dispensing harsh reagents that would damage other pumps, it also reduced the need for preventative maintenance.

Eliminating Potential Contaminants

It used to be particularly common during the assembly process of a pump to come across potential contaminant issues. The impact of the laser welding process, in which silicon oil is used and can become a contaminant, has the potential to cause many problems. The oils can react with other components and leave a residue in the final product. A reservoir seal that eliminates the need for using silicone oil provides a very flat line coefficient of friction, offering many benefits.

In addition, concerns over potential liability have driven many large silicone manufacturers to aggressively exclude themselves from providing silicone intended to be used in the human body for more than 29 days. Tubing used in pharmaceutical and biotech applications has particular requirements. Among the requirements for tubing is the ability to withstand the sterilization processes, the delivery of favorable test results regarding extractable substances, and the absence of animal-derived ingredients. Leaving many manufacturers to start only with processing components without animal or animal-derived ingredients.

Fig. 2 – It’s crucial to choose the right seal for the correct end use in exacting medical device applications.
Although medical-grade seals and tubing is sterilized prior to use, it makes sense to start with the cleanest possible product. Companies such as Abbott Laboratories, Pfizer, AstraZeneca, and Merck investigate the conditions in which the seal and tubing is manufactured, such as whether materials are produced in a cleanroom, the ISO level (6, 7, 8), how products are handled and stored after being manufactured, etc. They value whether a facility has been tested for contaminants by an independent laboratory.

For the diverse range of parenteral delivery platforms, including pre-filled syringes and blow/fill/seal technology, exposure of the product and container to the environment must be minimized.

Medical-Grade Tubing in Pumps

How long the tubing lasts in the pump and how long the pump itself lasts continue to be critical aspects to keep in mind. For instance, peristaltic pump tubing needs to withstand repeated compression and release without losing its shape, as oval or distorted tubing may not produce an even flow. The tubing also needs to perform consistently for pumping campaigns that can last many hours, so durability is a must. Related to that is how the tubing affects the pump. If the tubing is too hard or too soft, it may wear pump parts more quickly. Typically, the harder the pump has to work, the shorter its lifespan. Some tubing is designed specifically for pump use, while others are made for a variety of uses. These factors should all be taken into account during the tubing selection process for device manufacturers.

Due to the diverse range of drug delivery platforms, including blow/fill/seal technology and pre-filled syringes, it is important to work with an elastomer and thermoplastic materials provider that can offer a specific focus on addressing the needs of the life science industry. The suppler should have a diverse offering in the medical field that includes high-quality seals, bearings, hoses, and disposables for use in drug delivery systems.

The Impact of Reservoir Seals on Drug Delivery Systems

Parenteral drug-delivery systems are dramatically changing the manner in which drugs are delivered. Using reliable seals and connecting solutions enable designers to develop systems that permit the precise and continual delivery of medication to treat conditions such as diabetes, hepatitis, cancer, and chronic pain. (See Figure 2) Such delivery systems have certain requirements for the kinds of seals they use. They need to be low friction, chemically compatible, and deliver consistent seal performance, as well as increased service life, all of which can be provided with a technically engineered reservoir seal.

A pre-filled syringe is a single-dose packet of vaccine to which a needle has been fixed by the manufacturer. In the past, metal or glass syringes were popular, but increasingly there has been a movement towards pre-filled disposable systems. This has stimulated the demand for convenient and safe pre-filled syringes in the medical field over conventional glass vials for packing parenteral drugs.

Syringe Tip Seal and Pre-Filled Syringes

Providers of syringe tip seals or syringe plunger seals work in the categories of drugs packaged in pre-filled syringes encompassing vaccines, blood stimulants, therapeutic proteins, erythroproteins, interferons, and rheumatoid arthritis. Due to security, they anticipate many new products that must be injected should be pre-filled as they essentially eliminate the processes that are required before one uses a drug in a vial. Additionally, it helps eliminate dosing errors because pre-filled syringes contain the exact dose. Many pharmaceutical manufacturers overfill vials by up to 25% to make sure the end user is guaranteed to withdraw the dose required. However, this overfill can cause errors that are virtually removed with pre-filled syringes. This means less waste, especially if some vaccines are in short supply or are very costly.

Manufacturers’ Parenteral Packaging Challenges

One of the major challenges in this industry for manufacturers includes the interaction of pre-filled syringes with the drug. This causes great concern because it creates stability issues. Manufacturers need to eliminate the interaction between drugs and packaging materials. Regulatory bodies, companies, and customers will scrutinize every aspect of needles and syringes especially as they are being used more and more today. However, the use of disposable tips and disposable rubber plungers means that compliance and safety is easier to achieve.

Processing and quality control issues continue to be important. Manufacturing costs are rising, especially because of the growing concern of needle stick injuries and the implementation of safety measures around these injuries. The safety systems are very costly, and the safety system providers are continuously researching to develop low-cost alternatives.

There are a growing number of compounds in new therapeutic classes and the number of injectable products available is increasing. This means technology needs to adapt to these new innovations. This trend is likely to continue in the foreseeable future. If a greater number of new drugs are placed in prefilled syringes, the likelihood is that uptake of these by end users will increase, as they get used to this format. Manufacturers will be looking to keep up with demand. Pharmaceutical companies are requiring more sophisticated forms of delivery as their requirements become more complex.

From materials that perform in extreme temperatures or pressures, to compounds that resist challenging chemicals or meet stringent approvals, the correctly engineered reservoir seals used in pre-filled pens, pre-filled syringes, pen injectors, and auto-injectors lower friction, increase efficiencies, deliver more accurate dosing, and offer a more convenient single dose of manufacturers’ injectable products.

Medical Devices’ Use of Liquid Silicone Rubber

Fig. 3 – Hypoallergenic LSR provides a multitude of end uses for medical devices, not the least of which is due to its cleanroom capabilities.
LSR has been used in a range of medical devices, including seals, plungers, and gaskets in implanted and non-implanted devices, and as part of electronic medical devices. One specific application in which manufacturers use LSR is as buffering for lung catheters, where the catheter’s leading edge is bonded with soft LSR to prevent tearing of delicate lung tissue. Some other medical device applications well suited for LSR are as a top housing cover with a silicone vibration dampener, or a silicone sealing cap used for a medical device. (See Figure 3)

Wider applications of LSR are only limited by designers’ depth of experience, education, and creativity, and manufacturers’ experience and willingness to explore new innovative use of this medical material. The medical device industry is also showing a preference for LSR over alternative medical materials. Unlike latex rubber, which can produce sensitivity in some end users, LSR is hypoallergenic. Unlike polyvinyl chloride, it does not contain phthalates used as plasticizers, which have been found to disrupt the endocrine system and have caused reproductive and neurological damage in laboratory animal tests.

FDA Requirements and Material Benefits

For such medical applications, silicone must be tested for biocompatibility and must meet the necessary FDA requirements. Medical silicone applications are divided into two classes: restricted and unrestricted. Normally, restricted is referred to as short-term implantable and unrestricted is referred to as long-term implantable. Since LSR is biocompatible and hypoallergenic, it gives minimal risk of allergic reaction during its use. It is also hygienic, giving bacteria and fungi little chance to grow and spread. These are a few of the properties that make it ideal for use in implantable devices.

LSR also offers exceptional compression set properties and can be molded to varying wall thicknesses within the same part. These characteristics, together with the material’s durability and flexibility, have led to LSR becoming a critical component of medical devices.

Summary

Industry analysts are forecasting improved drug delivery and new formulations will be vital to pharmaceutical companies, increasing demand for innovative medical injection devices, pumps, and other devices. Pre-filled syringes form one of the fastest growing markets in healthcare. In 2012, 2.96 billion of those syringe units were sold. Medical device manufacturers are responding to pharmaceutical companies’ needs by engineering longer-lasting quality products and investing in better quality materials like those found in reservoir seals, which provide better performance in extreme temperatures or pressures, perform well when interacting with challenging chemicals, and meet stringent approvals.

In addition, medical device manufacturers are increasingly turning to extrusion and LSR molding capabilities and custom designs in silicone that are used in both disposable and durable equipment. This can enhance product performance, extend life and minimize planned maintenance of durable equipment, and lower overall device user costs. For manufacturers serving the medical industry, the most important factors are safety, stability, convenience, and cost-effectiveness.

This article was written by Marlee Rosen, Principal Analyst, Rosen Associates, Tampa, FL, for Trelleborg Sealing Solutions Americas, El Segundo, CA. For more information, Click Here .


Medical Design Briefs Magazine

This article first appeared in the September, 2014 issue of Medical Design Briefs Magazine.

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