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Medical device engineers are increasingly gravitating toward biomedical textiles to aid in implant performance, including cardiovascular applications such as structural heart implants or stent grafts. These textiles, which can be used to enable a broad range of functions such as occlusion, embolic protection, flow diversion, inhibiting restenosis, containing tumor growth, and maintaining vessel integrity, are chosen for the versatility they offer in product design. Textiles can be developed in 2D and 3D implantable forms, with configurations limited only by the imagination. However, understanding the breadth of possibility in textile manufacturing and determining the optimum textile design isn't as straightforward as it may seem. Here are the top 10 tips to consider for using textiles to fast-track the product development timeline.

1. Focus on Performance Not Process

Table 1. Checklist of design inputs to consider when benchmarking performance.

It may seem obvious, but many product designers will consider a predicate device design and use this as the basis to determine whether they need a woven, knitted, or braided textile solution. Taking this approach typically leads to a me-too solution without exploring the potential for substantial performance improvements. Keep an open mind regarding the manufacturing process, as there are numerous processing methods to obtain similar designs. The most important thing to do, at the outset, is to determine the exact dimensional specifications, followed by the required functional performance of the device; i.e., ask “what is it?” and “what does it need to do?”

2. Deliver Procedural Innovation

Product delivery fundamentally impacts product design, so when determining the basic criteria — what it is and what it needs to do — it is essential to understand how will it get there. It is also important to remember that effective product delivery can offer procedural innovation.

Transcatheter delivery, for example, creates dimensional limitations on implant size and makes the textile expansion profile integral to the design. Similarly during open surgery, the ability to place and secure the implant with ease is a distinct advantage.

The textile can be designed to facilitate delivery. For example, improving how the textile unfurls can enable placement, and textiles can be designed so that they simplify or incorporate anchoring technology. Even the feel of the textile implant in the surgeon's hands can play a role in successful procedural outcomes. Effective consideration of implant delivery and placement can play a critical role in product differentiation.

3. Determine the Pore Architecture

The round to flat suture is a unique suture design tailored for soft tissue repair. (Credit: Aran Biomedical)

The pore size and structure of an implant plays an integral role in its performance in vivo. On the one hand, pores control the flow of liquid, such as vessel occlusion, filtration, and blood flow diversion, or facilitate seroma drainage during the healing process. In this instance, the pore structure can range from blood impermeable to a macroporous design.

On the other hand, pore size can be optimized to encourage cell adhesion and tissue integration. To achieve this, it is necessary to get the appropriate balance in pore size to encourage cell adhesion without significant bacterial formation. Finally the pore size, as well as its shape, directly affects the mechanical performance of an implant, so square, diamond, or hexagonal pores, for example, provide different directional elasticity or shape memory.

4. Source the Right Resin

Don't underestimate the importance of choosing the right material. The raw ingredients of any design directly impact performance characteristics such as tensile strength, elasticity, resorption, durability, melt processing temperature, etc. Whether a device is planned for long-term or short-term implantation, it needs to be biocompatible and ideally have an established clinical history. It is important to remember that many traditional material suppliers no longer offer resins indicated for implantable use, so manufacturers need to source a “medical-grade” resin that is not contra-indicated for medical implantation.

5. Choose the Optimum Fiber

Choosing the right fiber is essential for any textile design. The basic questions to ask include “what is the dernier or dTEX (i.e., the weight of the fiber)” and “is it multifilament or monofilament?” Both of these criteria affect device design and performance. At a simple level, a multifilament textile tends to offer better tensile strength than a monofilament textile, and it may offer a denser textile structure. However, a multifilament textile can encourage greater bacterial formation. Fibers can also be twisted prior to processing to provide additional strength; there are a number of new fibers on the market offering higher performance for implantable textiles. Ultimately the choice of fiber will most likely be made on the basis of a range of performance criteria.

6. Rank Performance Criteria

To achieve the optimum balance of performance characteristics in a textile implant, it may be necessary to choose certain criteria over others, such as strength versus implant size, elasticity versus durability, etc. Understanding which criteria have the greatest priority helps optimize the design.

7. Benchmark Textile Performance

As mentioned, numerous textile processing methods are available to create an optimal implantable design, but whichever processing method is chosen, it is essential to benchmark performance against key inputs. See Table 1 for a simple checklist of design inputs to consider when benchmarking performance.

8. Control the Design

It's important to remember that modern textile processing equipment has highly effective PC controls. This allows for excellent design details to be incorporated, while ensuring accuracy and consistency. Implantable textile designs can now integrate multiple design configurations seamlessly within the one structure, and changing these key design inputs helps performance optimization.

An example of a knitted mesh textile. (Credit: Aran Biomedical)

9. Optimize Textile Design

Postprocessing can deliver clear product differentiation, so it's important to evaluate all options. Here are a few things to consider:

  • Trimming — Using laser cutting, a hot knife, stamping, or any cutting instruments, this process defines accurately the dimensional configuration for the implantable textile component. Remember that some mechanical trimming options can lead to the textile fraying.
  • Heat setting — This process ensures that the implantable textile maintains its dimensional configuration and pore structure.
  • Shape forming — This process converts the textile into a 3D structure, either to conform to an underlying implant or to a specific anatomical design.
  • Coating — Coatings can provide a performance advantage to textile implants (i.e., an impermeable seal, hydrophilic or hydrophobic properties, adhesive qualities, a radiopaque surface, placement indicators, etc.).
  • Component integration — Integration of textiles with other components is often required to expand product functionality. Bonding, suturing, or crimping are typical means to integrate textile implants with other textile components, nitinol frames, needles, anchors, and other implantable structures.
  • Design Configuration — textile designs can be elaborated by splicing loops or layering multiple textile configurations into one design, such as overbraiding.

10. Design for Manufacture

As with any design process, it is essential to consider design for manufacturing. From a textile perspective, this can include decisions around suturing versus bonding, hand sewing or machine sewing, integrated automated process steps, or even custom designed machinery. Undertaking this process helps to ensure that the product achieves the right balance in terms of design criteria, processing methods, and cost of manufacturing.

Summary

Biomedical textiles can aid in implant performance in many ways. Whether designing structural heart implants or stent grafts, textiles can enable a broad range of functions from inhibiting restenosis to maintaining vessel integrity. The versatility of textiles make them ideal for enhancing designs and, ultimately, improving product development.

This article was written by Dean King, Medical Textiles Programme Manager for Aran Biomedical, Galway, Ireland. For more information, Click Here.