Intelligent/Compliant Design

The use of FDA-compliant material allows faster commercialization of devices that incorporate biomedical fibers. Historically, scaffolds have been developed from a number of technologies, including non-woven fabric, polymer extrusion and molding, electrospun extrusion, die-stamping, polymer hydrogel compositions, and 3D printing. Only textile engineering using advanced biodegradable fiber compositions and controlled release design provides the researcher with precision design control. While many of the traditional processes are capable of providing acceptable research structures, the researcher must keep in mind that all of these material constructs must be prepared by using FDA-compliant materials if the objective is to get to the commercial level.

Unfortunately, this critical compliance fact is systematically disregarded in biomedical research. It is not enough to solve the problem with an engineering process — the materials of composition or construction must all comply with federal regulations for device commercialization to go forward. An additionally important adjunct to textile engineering is precision structural architecture. Many of the other technologies mentioned above, such as electrospun or non-woven fabric, are subject to poor mechanical properties and enormous dimensional instability with small changes in environmental conditions. Here, too, the need for precision is critical to regulatory quality requirements.

The attractive feature of biomedical textile engineering is the host of available, FDA-approved synthetic, biodegradable polymers. Selecting fibers or yarns designed from these compliant feed-stocks results in a compliant end product, eliminating the need to modify the extrudates with unregulated processing aids or chemicals during the fiber melt-flow process. The choice of compliant master-batched polymers in biomedical melt-flow textile scaffolds removes the unnecessary burden of separately testing the chemical or polymeric components of the device for safety. This is an intelligent design approach to scaffold building.

Managed Degradation

The custom design of tissue scaffolds using biomedical textile fibers offers critical advantages in managed degradation.

An important design control in scaffold development is to avoid what is known as a scaffold collapse or scaffold crash. Avoiding these malfunctions requires attention to the simultaneous activities of tissue growth and scaffold degradation. As the organ develops, it must penetrate the engineered scaffold and establish tissue mass as it organizes into organ form. In tandem with this tissue growth, the scaffold degrades and diminishes in both material mass and structural integrity. If the scaffold degrades more rapidly than the maturity of the tissue mass, or if the accumulation of tissue mass increases beyond the scaffold’s structural integrity, then the scaffold collapses and the tissue growth process fails, not to mention that the engineering effort is lost.

In an important innovation, new biodegradable polymer compositions can allow the designer control over the timing of degradation in ways unavailable just a decade ago. Multi-layer cell-bed constructs with support filament reinforcement can extend exposure periods to provide prolonged stages of scaffold physical stability. And in difficult anatomies, these advanced compositions allow for the design of hybrid degradable, non-resorbable structures.

By choosing the appropriate fiber and yarn composition, a design engineer can create a scaffold that manages degradation. Some biodegradable polymers like polyglycolic acid (PGA) degrade quickly, whereas biodegradable polymers like polylactic acid (PLA) have extended resistance to biodegradation. Combining or intermingling yarn stocks in a braided structure made from a combination of PGA and PLA yarns can precisely extend the engineering strength beyond the degradation period of a yarn made entirely of PGA. And likewise, biodegradable polymers can be intentionally customized to create a single copolymer of specific PLA/PGA ratios that further manages the degradation time in a single yarn sample. Additionally, an assortment of engineering properties can be designed-in using other monomers as feed stocks. These important and innovative “precisely managed degradation” design features are difficult if not impossible to achieve with a non-woven structure. The key word here is precisely — that is, the success factor is repeatability. These structures, when composed of standardized yarn or fiber chemistries, define their own quality control.

In addition to the basic polymer composition, advanced fiber technology allows the engineer to design fiber crosssections with both the internal and external architectural features coupled with the potential to spatially incorporate bioactive compounds for temporal release throughout time-controlled degradation.

Medical Design Briefs Magazine

This article first appeared in the August, 2012 issue of Medical Design Briefs Magazine.

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