Lectures in capstone design courses provide an opportunity to present information needed by students to properly execute their projects and/or prepare them for their careers. They can be used to supplement reading assignments or introduce new material not presented elsewhere in the course or biomedical engineering curriculum.
Three design topics that are often ignored in biomedical engineering curricula are the packaging, labeling, and sterilization of medical devices. Packaging and labeling are an important part of the final product and must be considered when designing a new medical device. Sterilization methods can affect the material properties and device performance and should also be considered during the design process. Students do not need to become experts in these areas, but they do need to know that they must consider these when designing medical devices.
Knowledge of these topics may not be necessary to complete capstone design projects but will help prepare our students for careers in the medical device industry. As project managers, they will need to include tasks related to packaging, labeling, and sterilization in their project schedules. At the four medical device companies where I worked, packaging design was the responsibility of 1) degreed packaging engineers, 2) mechanical engineers who focused on package design, or 3) packaging vendors who designed and supplied packaging for new products. In each company, packaging designers worked closely with design engineers. Similarly, there were in-house regulatory specialists who helped develop label copy for all product labels, and there were in-house or outside experts who helped determine appropriate cost-effective sterilization methods.
Students interested in careers in new product development, with an understanding of the fundamentals of packaging, labeling, and sterilization, will have an advantage over others. To provide students with a basic knowledge of these topics, the information contained in the following paragraphs would be a good starting point for inclusion into a capstone design course.
Packaging
The role of the product package is to ensure that after the product is shipped, delivered, stored, and eventually opened for use by the customer, it is sterile and functional. The package must prevent damage to the product during shipping and storage and prevent damage to the sterile seal while it sits on the shelf throughout the expected shelf life. To do this, it must withstand the stresses of shipping (e.g., vibration, impact loads, and environmental conditions) and storage (e.g., temperature and humidity). Other requirements include serving as a barrier to microorganisms and humidity; keeping out dust, dirt, and other contaminants; and providing a method for transferring the device to the sterile field while maintaining sterility and not contaminating the sterile field. Packaging should provide quick access to the product and not generate debris when opened in the operating room. It should allow for quick, easy identification of the product and make efficient use of space. This is often addressed by using clear packaging and labels that do not block the view of the device. Packaging that can lay flat and nest, is stackable, and allows labels to be viewed during storage helps make the most efficient use of storage space. Packaging should be designed to provide the appropriate spacing, location, and orientation of the components contained in the package.
Labeling
According to the U.S. Food and Drug Administration (FDA), labeling includes product labels, package inserts, user manuals, sales literature, and communications with customers. Product labels provide identification of the product as well as warnings (e.g., temperature restrictions, humidity warnings, and single-use statements), lot numbers, manufacturers, expiration dates, and method of sterilization.
Design engineers are often involved with developing package inserts that contain instructions for use, precautions, what to do if there is a problem while using the product, and other information. Although engineers rarely create sales literature, they may be called upon to review the copy generated by marketing and sales personnel for truth and accuracy. When speaking to potential customers (e.g., surgeons, physicians, and nurses), engineers (and other company personnel) must be careful not to verbally make claims about a medical device that have not been tested or proven.
Sterilization
There are several methods used to sterilize medical devices. Each has limitations and exposes products to different temperatures and pressures that can affect product function. The selection of an appropriate sterilization method is determined by the material to be sterilized as well as specific design features that may be part of the product. Selection of packaging materials is typically determined by the sterilization method used. The most commonly use methods include:
Steam sterilization (often performed with an autoclave, commonly used in hospitals)
- Thermal energy from steam is used to kill microbes through the coagulation of proteins, causing denaturation of DNA and destruction of vital enzymes [1], [2].
- Product is exposed to high temperatures (121 °C) and high humidity.
- Process is incompatible with most polymers due to melting temperatures below steam temperature; compatible with metal devices.
- Porous packaging materials are required to allow steam to enter the package and contact the surface of the device.
Ethylene oxide (EtO)
- EtO gas kills microbes via chemical reactions with nucleic acids [1].
- The process results in a temperature increase (60 °C).
- A high relative humidity (50–70%) is used to allow EtO to interact with water deposited on the surface of the device.
- Pressure cycling is used to alternatively pump in and evacuate EtO gas.
- Porous packaging is required to allow EtO gas to penetrate the package and contact the surfaces of the device.
Radiation (gamma or electron beam)
- Radiation energy produces free radicals that react with nucleic acids, damaging nuclear material or cytoplasmic structures [1].
- Radiation can penetrate all packaging materials.
- Polymers can degrade and discolor due to chain scission, which can reduce the molecular weight and physical properties such as tensile strength.
- Radiation has no effect on metals.
- Nonporous or impervious materials such as vapor barriers and metal foil pouches can be used.
Other methods include dry heat, gas plasma, and liquid chemical sterilization.
Marketing Issues in Packaging Design
Packaging can be a significant feature of a product. It can differentiate one company’s product from others and reinforce product positioning in the market as a high- or low-end device. If designed properly, it can provide value to the customer by offering convenience, minimizing storage space, and helping maintain a reasonable product cost. For some products, packaging can influence the buying decision depending on how well the packaging meets the storage, dispensing, and disposal needs of the hospital.
Examples of commonly used materials for medical devices include:
- Spun-bonded polyolefin (Tyvek)—hydrophobic, high gas permeability, high strength, keeps out microbes, and allows penetration of air and EtO gas for EtO sterilization. It is typically coated to allow for heat-sealing of the pouch to create a sterile seal.
- Films—extruded layers of polymers such as polyethylene or polypropylene—nonporous, can be used with electron beam sterilization and other methods, and are heat-sealable.
- Foil laminates—coated aluminum, nonporous, barrier to microbes, water vapor, and gas. Heat-sealable and often sterilized using gamma radiation.
- Kraft paper—porous to water vapor and air, microbial barrier, often used for steam sterilization in hospitals.
- Thermoformed polymer trays with heat-sealed adhesive-coated Tyvek lid—often used for EtO sterilization.
To facilitate learning about packaging, samples of packaged medical devices that students can see and handle can be used to illustrate packaging design concepts. Instructors can contact local or regional packaging vendors and request samples of packaging materials commonly used for medical devices or they can contact medical device companies directly and request sample packaged products for educational purposes. Sometimes, local medical device sales representatives or hospitals may have older, expired medical devices that they can donate for use in the classroom.
Showing some of the most common symbols used for medical device labels and asking students to guess what they mean can create interest in labeling. ISO 15223-1:2012 Medical Devices—Symbols to Be Used with Medical Device Labels, Labelling and Information to Be Supplied—Part 1: General Requirements provides a list of international medical device symbols and their meanings. Other standards of interest for package testing and sterilization methods include ASTM D4169-14 Standard Practice for Performance Testing of Shipping Containers and Systems and ISO 11135:2014 Sterilization of Health-care Products—Ethylene Oxide—Requirements for the Development, Validation and Routine Control of a Sterilization Process for Medical Devices, respectively.
Conclusions
In summary, a medical product includes both the device and the packaging used to protect the device during sterilization, shipping, and storage. Device design (material and geometry) often determines the sterilization method used, which then, along with cost requirements, determines the package design. Labeling requirements are specified in various international standards and FDA regulations. Familiarity with the fundamentals of medical device packaging, labeling, and sterilization methods can help prepare students for careers in medical device design and would benefit students if included in biomedical engineering capstone design courses.
References
- Medical Device Packaging Handbook, 2nd edition, M. Sherman, Ed. New York: Marcel Dekker, Inc., 1998.
- Sterilisation of Biomaterials and Medical Devices, S. Lerouge and A. Simmons, Eds. Cambridge, U.K.: Woodhead Publishing, 2012.