Tissue engineering - Orthopaedic Biomaterials in Research and Practice - page 226

Tissue Biologics

Devices

FIGUre 9.1 (See color insert.) the intersection of tissue, biologics,
and medical devices in the field of tissue engineering.

as the merging of clinical medicine (such as prosthetics, reconstruc-
tive surgery, transplantation medicine, and microsurgery) and biology
(cell biology, biochemistry, molecular biology, and genetics). As such,
tissue engineering can be defined as the application of the principles
and methods of engineering and life sciences toward the fundamental
understanding of structure-function relationships in normal and patho-
logic mammalian tissue and the development of biological substitutes to
restore, maintain, or improve function (Figure 9.1). Tissue engineering
has evolved from cell biology and in vitro cell culture in plastic and
reconstructive surgery to microvascular tissue transplantation in whole
organ transplantation surgery.
Tissue-engineered medical products are evolving treatment options for
musculoskeletal conditions and diseases. The products include cells, tis-
sues, and inorganic and organic substances used alone or in combination
with other factors that are manufactured, manipulated, or altered in a labo-
ratory. They may be used for the repair, restoration, or regeneration of liv-
ing tissue. They also may include substances that are not found naturally
in tissues or whose normal physiologic concentration has been altered.

Synthesis methods

Tissue-engineered products are often built from three-dimensional (3D)
structures known as scaffolds. Cells are implanted or seeded onto these
scaffolds, which help with cell attachment, delivery and retention of
cells and biochemical factors, and diffusion of cell nutrients and cell-
expressed products.
Cells are cultured by controlling the oxygen, pH, humidity, tempera-
ture, nutrients, and osmotic pressure. Nutrient and metabolic transport
via diffusion is a necessary condition for maintaining culture conditions.
The functionality of a tissue culture may also require a capillary network
or the introduction of growth factors, hormones, chemical stimuli, and
physical stimuli. Some cells respond positively to mechanical stimuli