Scaffold Collapse Into Non-Wovens
Non-woven scaffolds are particularly susceptible to scaffold collapse for a number of reasons. First, the non-woven process has limited pore size control as a result of the random accumulation of fiber that is compressed into a mat before forming the scaffold structure. This variability in pore size can retard the cellular migration into the bulk structure if the pores are too dense.
Second, even if it were possible to coextrude two fibers with varying degradation rates into a single non-woven structure, it is difficult to precisely, or repeatedly, compress the mass into a uniform mat. The accumulation of fiber creates a random pattern from the drop-down source. The random accumulation of two dissimilar polymers can influence degradation rates, which can lead to pockets of degradation and result in uneven degradation patterns and unexpected collapse.
Third, the random pattern of the nonwoven eliminates any chance of engineering- in either structural strength patterns or anatomic geometries, such as contour guides or circumferential alignment. Here, the use of textile engineering technology offers an innovative feature: The textile structure can be designed to not only enhance strength, but to also approximate biomimetic structures. Adding the ability to select the advanced polymer compositions of the fiber or yarns allows the bioengineer the option to design-in controlled release and degradation of the scaffold matrix.
Functional Conversion and Remodeling Enable Recruitment
The aforementioned features are physical advantages of textile structures coupled with chemistries of construction. A biodegradable organized textile scaffold structure offers the tissue engineer another advantage: controlled functionality. For instance, once a scaffold is constructed using textile technology, the structure can be chemically post-treated to expose chemical functional groups to which trophic agents can be bound.
A structure having a designed-in specific PGA-based composition can easily convert PGA surface functional ester groups to hydroxyl and carboxylic acid groups by simply exposing the structure to a dilute aqueous solution of potassium hydroxide (KOH). These newly exposed functional groups can be selectively bound with any one of a number of bioactive compounds to enhance recruitment. The benefit of this conversion is that yarns and structures can be designed to have sacrificial sites, thus optimizing engineering strength integrity as a result of the surface treatment.
Finally, these textile engineered scaffolds can be remodeled. The basic superstructure of the design can be further modified at the microstructural level with hydrogels, bioactive coatings, spatially resolved droplet deposits, electrospun fiber fine networks, as well as application technologies that will provide gradient custom enhancements of the spatial geometry.
Biomedical textile engineering affords critical innovations in scaffold design, particularly where structural repeatability, spatial geometry, and engineering strength support the cellular processes in a consistent fashion. These factors illustrate the important impact that the convergence of a traditional installed base of engineering techniques, combined with new materials, offer for successful advances in regenerative medicine.
This article was written by Peter Gabriele, Director of Emerging Technology for Secant Medical, Perkasie, PA. For more information, visit http://info.hotims.com/40436-162.