Bioactive Glass-Based Coatings and Modified Surfaces: Strategies for the Manufacture, Testing, and Clinical Applications for Regenerative Medicine - Biological and Biomedical Coatings: Processing and Characterization - page 415

TABLE 9.21
Ideal Scaffold D esign Requirements

Design
Requirement Description

1 Act as a template for tissue growth, while maintaining 3-dimensional structure of

host tissue during tissue regeneration.

2 Should not elicit scar tissue formation.

3 Have a porous structure (similar to trabecullar bone) with interconnected pore

network allowing tissue growth in 3-D.

4

Pore interconnects should have apertures greater than 100 μm to allow cells to
migrate throughout the scaffold, in addition to allowing the fluid flow throughout
the scaffold.

5 Pores' surface textures should mimic ECM form and function: support cell

attachment, growth, and generation of extracellular matrix.

6 Resorbability matching host tissue growth/replacement rates.

7 Act as a delivery system for time release of chemical species (e.g., ions, growth

factors) enhancing bioactive response.

8 Capable of being mass-produced for clinical application.

1. Acellular scaffolds have been used to initiate repair of host tissues in situ. Scaffolds
have consisted of a biomaterial matrix coupled with biomolecules.

2. Cellular scaffolds have been preseeded/loaded with either stem cells or differenti-
ated cells before implantation. These scaffolds mature in vivo.

Synthetic polymers have received considerable research focus as scaffold materials because
their chemistries can be precisely controlled resulting in their ability to biodegrade at rates
determined by their surface chemistries [43]. However, they are not bioactive. Strategies to
introduce bioactivity in porous polymeric scaffolds have included:

1. Polymer-based scaffolds coated with ceramic (glass) particles

2. Ceramic (glass) scaffolds coated with a polymer

Polymers lack osteoconductivity [44]. The incorporation of bioactive ceramics and glasses
(e.g., hydroxyapatite, calcium phosphates, and Bioglass) in combination with biodegrad-
able polymers (e.g., poly(dl-lactic acid) (PDLLA)/bioglass, collagen/hydroxyapatite,
poly(hydroxybutyrate- co -hydroxyvalerate)/wollastonite, poly(lactic- co -glycolic acid)/HA,
polycaprolactone/calcium phosphate) have been explored to develop composite scaffolds
[44]. Strategies used to functionalize polymeric surfaces via the introduction of bioactive
glasses include cold pressing and slurry dipping.

Cold Pressing
The use of cold pressing was first reported by Stamboulis and coworkers [45]. By cold
pressing at 100 to 160 mPa, Bioglass powders (less than 5 μm) onto the surface of Polyglactin
910 (Vicryl ® ) sutures, they were able to coat the sutures. Although the coatings were not
uniform, the effect of Bioglass coating did not significantly alter the tensile properties of
the suture.
Ross and coworkers [46] developed a method for coating silicone tubing (with perito-
neal dialysis catheters) bioactive glasses using prewashing of the silicone tubing. Catheter