Insulin pump manufacturing requires intense technical precision, especially when it comes to selecting seals.
Drew Rogers, global director of healthcare & medical, Trelleborg Sealing Solutions
With more than 400 million adults worldwide suffering from diabetes and 1.5 million deaths directly attributed to the disease each year, it’s no wonder so many scientists, inventors and pharmaceutical companies are turning their attention to improving insulin delivery devices.
Diabetes is not only one of the most common chronic diseases; it is also complex and difficult to treat. Insulin is often administered between meals to keep blood sugar within a target range and at mealtimes based on the number of carbohydrates to be ingested. Basal insulin, also known as background insulin, is made by the pancreas and is the constantly present insulin in the body. While Bolus insulin is that extra insulin that the pancreas delivers in response to glucose ingested through meals. Insulin delivery devices aim to treat diabetes through adequate basal-bolus therapy.
A variety of insulin types are used to regulate blood-sugar levels, including fast-acting, short-acting, intermediate-acting, long-acting and pre-mixed. These are introduced into the body via a wide variety of devices, including traditional syringes, injection ports, insulin pens, conventional insulin pumps and patch pumps.
Current delivery devices
At present, insulin delivery devices go from extremely traditional to cutting edge. Following are overviews of each.
- Syringes. Direct, subcutaneous insulin injection through a needle and syringe remains the most common form of delivery. Selection of needle gauge, needle length, and syringe capacity are made by the patient together with his or her healthcare provider.
- External pumps. External insulin pumps remain relatively expensive, but many people with diabetes prefer them for their precision and, thus, their ability to provide strong control over blood glucose (measured by A1C levels). When connected to CGM (continuous glucose monitoring), these devices deliver a continuous basal dose of insulin and a bolus dose at mealtimes.
- Implantable pumps. Research teams around the world are developing implantable insulin pumps to measure blood glucose levels and provide a precise insulin dose. The small, lightweight pumps are surgically implanted and can deliver both a continuous basal dose of insulin and a bolus dose (through an outside controller).
- Pens. Insulin pens are an excellent way to transport insulin and allow patients to discreetly administer a dose. Pens are available as disposable one-shot devices and as long-term devices with replaceable or refillable cartridges. Eli Lilly and Companion Medical recently won FDA approval of a Bluetooth-enabled insulin pen that communicates dosing information to a smartphone app.
- Insulin injection aids. This category is intended to make injecting insulin easier, for example, for children and those with needle phobias. Once the device is installed, it’s used as the injection site for a three-day period.
Several other delivery device types are in development, including those that allow an insulin dose to be inhaled through the mouth, going directly into the lungs where it’s absorbed and passes into the bloodstream. Dry insulin devices have yet to become widely used because of dosage issues, but “wet” devices are being developed that deliver an individualized liquid dose to the lungs via new vibrating mesh micro-pump technology.
Another exciting pump technology development is the ability to use pumps together with glucose sensing technology (known as an artificial pancreas) that administers insulin based on actual glucose levels as determined by the glucose sensor. Insulin delivery is halted once a pre-programmed glucose level threshold is met.
Insulin pump technology
There are several advantages to insulin pumps, especially with the newer devices, over traditional injections. In addition to eliminating the need for injections at work, shopping, out to eat, etc., pumps are highly adjustable, allowing the patient to make precise changes based on exercise levels and types of food being consumed.
Pumps comprise an insulin cartridge, a battery-operated pump and a computer chip that allows the patients to control dosage. The current generation of pumps are small enough to be worn discreetly under most clothing and newer pump models don’t require tubing. The device is placed directly on the skin and dosage adjustments are made through a controller that can be carried in a purse or pocket, with a six-foot range most common.
However, manufacturing insulin pumps requires a high degree of technical precision, especially when it comes to selecting elastomeric components and particularly seals. Not only are there stringent regulatory requirements to consider, but also factors such as insulin compatibility and sterilization process compatibility. Other considerations include friction, lifecycle expectancy, cost, breakaway forces, and ongoing material availability.
Factors affecting seal selection
Geometry is an extremely important factor when selecting seals for insulin pumps.
The geometry determines the degree of force of the pump, its coefficient of friction, and its hydrodynamic qualities. The seal must be matched with the required dose measurement, the way the needle will be voided after use, and whether or not several “lay downs” on the bore of the syringe will be needed.
The correct material choice is essential to ensuring the seal will not degrade prematurely, fail due to an incorrectly matched application condition, or cause unwanted effects to contact media. Because thousands of configurations of plastic and elastomeric compounds are available, it’s important to have a seal supplier with the engineering resources and knowledge to properly select the correct material for your design.
Factors to consider include the material’s ability to be sterilized, availability, leachability and extractability, along with applicable regulatory requirements. In addition, many USP Class VI-compliant coating and surface treatment options are available to provide antimicrobial, lubricity, membrane and other properties to seals. Keep in mind that coatings are usually a secondary process on a seal. Not only the seal, but also the coating must be rigorously tested to ensure it will not have a negative impact on the device’s functionality.
It’s critical to fully vet your proposed seal design through prototyping to ensure it will pass regulatory scrutiny and the manufacturing process. When selecting a seal supplier, it’s important to choose one with a deep understanding of seals used in insulin pumps and the regulatory requirements with regards to engineering, quality control, and material. The supplier must have adequate resources to help determine the most optimal sealing solution for the pump design, including but not limited to material compatibility testing, prototyping options, non-linear finite element analysis (FEA), and lifecycle testing capabilities.
For those struggling with the complexities of insulin-dependent diabetes, the idea of more automated, less intrusive ways to manage their disease is a welcome change. New lighter, smarter devices paired with sophisticated drug delivery systems will ensure that patients with this chronic disease can be as active and healthy as possible.
Device manufacturers are focusing on taking advantage of the growth and new technologies around the insulin delivery device market. Working with suppliers that have the adequate expertise and the latest engineering techniques will be essential in order to bring innovation to market in the shortest development time possible.
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Robert Mirviss says
Great article! When I worked for Trelleborg, I had the opportunity to work on multiple medical applications, including insulin delivery devices. I’ve found the key points were fit, function, and sterilization. A deep understanding of the application and available materials goes a long way in the seal design. These were typically challenging and rewarding applications to work on.
Chris Newmarker says
Thanks for the insights, Robert.