Biomedical Engineering Reference
In-Depth Information
loskeletal tissues that are currently being engineered using these key compo-
nents include cartilage [22-27], bone [18, 28-32], muscle [33], tendon [34],
and IVD [35-37]. The various tissue engineering approaches can be broadly
classified into three main categories: (i) guided tissue regeneration utilizing
the natural regenerative ability of the tissues; (ii) cell therapy using either al-
lograft or autograft cells; and (iii) scaffold-supported cell therapy. Notably,
polymers play a pivotal role in each of these approaches as scaffolding mate-
rial which will be discussed below in more detail.
2.1
Biomaterials for Guided Tissue Repair
Guided tissue repair relies on the natural ability of the body to regenerate the
lost tissue. In this approach a suitable polymeric scaffold is implanted into the
defect site. The primary purpose of this scaffold is to provide mechanical sup-
port to enhance migration of cells, which have the ability to proliferate and
produce the tissue matrix, from the neighboring tissues into the defect site
as illustrated in Fig. 1. The biomaterial also acts as a barrier and occludes the
entrance of undesirable cells. In more advanced approaches, biomaterials are
also used to deliver growth factors and gene delivery vectors to the defect site
so as to accelerate the regeneration of tissue. The growth factors diffuse into
the neighboring tissue and bind to the cell receptors and accelerate their mi-
gration into the defect site. An ideal biomaterial for this purpose is expected
to navigate the tissue regeneration process by providing necessary cues for
Fig. 1 a
Guided regeneration of damaged tissue. A composite scaffold, containing hydro-
gels and bioactive molecules, is placed onto the defect site. The scaffold enhances the
migration of progenitor cells from the surrounding tissue into the defect site and subse-
quently regenerates the lost tissue. The bioactive molecules diffuse out of the scaffolds
and bind to the neighboring cells so as to accelerate the migration of cells into the defect
site.
b
Cell therapy. Allograft cells are encapsulated within a closed polymer membrane
system to allow exchange of nutrients, oxygen and biotherapeutic substances between the
encapsulated cells and the surroundings.
c
Cell-scaffold system. A cell population which
has the ability to produce the lost tissue is placed onto the defect site after encapsulating
within a promising scaffold system
