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 414

2. Cell. Scaffolds can be preseeded in vitro with cells normally present at the host
tissue site or recruited into in vivo, guiding them toward tissue reconstruction

3. Biological signals. Used to influence the local regulation and distribution of extra-
cellular signaling molecules (at the local, systemic, and remote consequences)
required for specifically designed cellular stimulation.

For regeneration of bone, the ability to control bioactivity and resorption coupled with the
potential of mimicking ECM to elicit specific biologic responses in vivo make bioactive
glasses ideal potential candidates for implant scaffolds and coatings supporting bone tis-
sue regeneration.
Salih [41] states that “A scaffold is a temporary support structure seeded with viable cells
coupled with a suitable culture environment to support the development of functional tis-
sue.” For tissue-engineering applications, a scaffold needs to be multifunctional serving
the considerations stated in Table 9.20.
The most important criteria for porous scaffolds are biocompatibility, and where appropri-
ate, vascularization [42]. For bone regeneration, the ideal scaffold should posses the design
requirements stated in Table 9.21 in order to address the tissue characteristics not addressed
by current bone replacement materials.

Coatings on Tissue-Engineering Scaffolds

Coating with bioactive glasses can functionalize scaffold surfaces, thus significantly improv-
ing, and in some cases introducing, bioactivity.

Polymeric Scaffolds

The choice of scaffold material is very important. For bone applications, it must serve all
the required design criteria stated in Table 9.21. Scaffolds are currently utilized in the fol-
lowing two ways:

TABLE 9.20
Design Considerations for Scaffolds to Be Used in Tissue Engineering Applications

BeforeImplantation At/DuringImplantation DuringImplantLifetime

Host the cells of interest plus
biological molecules (e.g.,
extracellular matrices,
growth factors, and
differentiation agents)

Be permanently implanted in vivo
Have a three-dimentional, porous
structure
Have the appropriate host-site
mechanical stability
Be biocompatible at the host tissue
site resulting in tissue regeneration
and growth
Try to mimic the ECM by exhibiting
suitable physical and chemical
properties to facilitate cell
immobilization, migration,
proliferation, and differentiation
into a mature phenotype coupled
with production and maintenance of
extracellular matrix

Be able to mature while maintaining
viability
Allow adequate perfusion of
nutrients and waste
Possibly support appropriate
vascularization (depending on
implant site)