Materials Selection for Sterilization
The sterilization process plays a big part in the materials selection of products as part of the product development process. Consider the following key points for sterilization during the product design phase that will greatly enhance downstream supply chain development:
1. Impact of supply chain cycle
As medical devices are becoming increasingly complex, the use of exotic materials is becoming a popular development route. This is true especially in combination products, drug-delivery devices, and certain orthopedic implants. Bio-absorptive materials, biologics, proteins, and other engineered polymer composites with high porosity tend to retain sterilant residuals used during the sterilization process. The impact of increased levels of residuals not only impacts safety of patients, but also lengthens required post-sterilization aeration time considerably. Alternatively, sensitivity of these materials relative to irradiation may require extra processing steps to ensure product integrity is not compromised.
2. Material integrity
Irradiation sterilization processes involve energy transmission through the packaging to inactivate microbiological activity. Alternatively, gas sterilization processes introduce chemical sterilants to achieve sterilization. These processes may have a negative impact on overall product integrity. For example: Ultra-high molecular weight polyethylene (UHMWPE), used primarily for the manufacture of the acetabular cup for total hip replacements and the patellar components for total knee replacements, has been reported to have occasional failures within 6 – 8 years of implantation in the case of active or heavy patients. Most failures are attributed to the oxidative degradation of the PE molecules initiated by the reaction of free radicals, that are generated by irradiation during sterilization. These effects occur during shelf storage and implantation.
3. Product cost control
In order to accommodate specific sterilization methods, materials may be limited to a few categories that are resistant to the impact of sterilization processes. This often translates into higher material costs. Additionally, in the case of ethylene oxide, prolonged aeration times mean higher working capital and inventory costs for the production lot. This will also add supply chain risk with bigger lot sizes.
4. Logistical flexibility and supply chain risk
Most sterilization facilities offer service in a limited geographic proximity, typically about 200- to 300-mile radius. A good risk mitigation strategy is to develop products that can be sterilized by methods and vendors that are close to the manufacturing facility. Multiple vendor options is a best practice in any supplier selection process.
Sterilization is a part of a complex process that involves product development and supply chain. However, if appropriate measures are taken, product development effectiveness and supply chain efficiencies can be maximized at the same time. The following checklist will aid in your decision-making process with respect to sterilization methods:
a. Consider materials compatibility with sterilization process early on
b. Design for manufacturing with sterilization process in the consideration
c. Understand the physical properties of materials you are selecting, e.g. interaction with irradiation, heat sensitivity
d. Select multiple sterilization vendors based on technology and geographic proximity
e. Evaluate how each sterilization process and its technology presents advantages and limitations to the overall material selection
f. Consult a sterilization development consultant for an evaluation of your product and development process