Biomedical Engineering Reference
In-Depth Information
Tissue engineering can be approached in three ways. 42,190 First, freshly
isolated or cultured cells are implanted to treat diseased or injured tissues.
The cells can be manipulated before implantation to suit the needs of the patient.
Implantation eliminates possible complications and morbidity associated with
surgical procedures 42 but is limited by the cells being washed out from the site
of injection and the inability of the implanted cells to maintain proper function.
The second approach involves in situ tissue regeneration by implanting the scaf-
folds or injecting tissue-inducing substance at the injured site. In this approach,
the tissue-inducing materials need to be purified and a selection of appropriate
delivery methods needs to be applied (i.e. controlled delivery, soluble factors). 42
The last approach is in vitro implantation of functional tissues engineered from
cells and scaffolds. For this approach to work out, the mechanical and biochem-
ical properties of the scaffolds must be optimized as well as the cell ratio and
density 42 because tissue engineering requires attention to the type of materials
to allow a healthy growth of the cells for the tissue.
Tissue engineering is an area of medicine where biocompatible nanomateri-
als finds excellent applications. It is a multidisciplinary field that uses knowl-
edge in chemistry, physics, engineering, life, and clinical sciences toward the
development of solutions to critical medical problems such as tissue loss, organ
damage, and organ failure. 127,190 It requires the understanding of structure and
function relationships in tissues in order to carry out the development of bio-
logical substitutes that restore, maintain, or improve tissue function. 216 During in
vitro engineering of living tissues, cultured cells are grown on bioactive degrad-
able substrates called scaffolds that serve as guide as well as provide the physical
and chemical cues to the cell differentiation and assembly into 3D structures.
Healthy cellular growth, proliferation, and support for new tissue formation
require specific physical, mechanical, and biological properties of the scaffolds.
These required properties of biomaterials that can be achieved through fabrica-
tion technologies are very important in the design of the scaffolds to stimulate
specific cell response at the molecular level. The scaffolds must elicit specific
interactions with the cell to allow direct cell attachment, proliferation, differ-
entiation, and ECM production and organization. Thus, the selection of appro-
priate biomaterials is the major factor for the success of tissue engineering. 217
For successful tissue regeneration, the scaffold must consist of biocompatible
surfaces with appropriate mechanical properties that mimic the cells environment
for healthy proliferation.
Scaffolds are artificial structures that support 3D tissue formation allow-
ing cell attachment and migration and deliver and retain cells, and biochemi-
cal factors enable diffusion of vital cell nutrients and expressed products. 127
Scaffolds must possess sufficient porosity and pore connectivity to facilitate
cell seeding and diffusion of cells and nutrients and increase the specific
surface area available for cell attachment and tissue ingrowth for a uniform
distribution of cells and the adequate transport of nutrients and cellular waste
products. 218,13,219
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