Biomedical Engineering Reference
In-Depth Information
generally used in this application. The action of bacterial collagenase on collagen is different from that
of mammalian collagenase (Woolley, 1984). In addition, the enzymatic activity used in
in vitro
studies
is arbitrarily defined. Thus, the data generated from the bacterial collagenase should be viewed with
caution. The bacterial collagenase digestion studies, however, are useful in comparing a prototype with
a collagen material of known rate of
in vivo
resorption.
Each of the above parameters should be considered in designing a resorbable implant. The interde-
pendency of the parameters must also be balanced for maximal efficacy of the implant.
6.4 Tissue Engineering for Tissue and Organ Regeneration
Biomedical applications of collagen have entered a new era in the last decade. The potential use of col-
lagen materials in medicine has increasingly been appreciated as the science and technology advances.
One major emerging field of biomedical research which has received rigorous attention in recent
years is tissue engineering. Tissue engineering is an interdisciplinary science of biochemistry, cell and
molecular biology, genetics, materials science, biomedical engineering, and medicine to produce inno-
vative 3-D composites having structure/function properties that can be used either to replace or correct
poorly functioning components in humans and animals or to introduce better functional components
into these living systems. Thus, the field of tissue engineering requires a close collaboration among vari-
ous disciplines for success.
Tissue engineering consists primarily of three components: (1) extracellular matrix, (2) cells, and
(3) regulatory signals (e.g., tissue-specific growth factors). One of the key elements in tissue engineering
is the extracellular matrix which either provides a scaffolding for cells or acts as a delivery vehicle for
regulatory signals such as growth factors.
TABLE 6.6
Survey of Collagen-Based Medical Products and Research and Development Activities
Applications
Comments
Hemostasis
Commercial products: sponge, fiber, and felt forms are used in cardiovascular (Abbott and
Austin, 1975), neurosurgical (Rybock and Long, 1977), dermatological (Larson, 1988), ob/gyn
(Correll et al., 1985), orthopedic (Blanche and Chaux, 1988), and oral surgical applications
(Stein et al., 1985)
Dermatology
Commercial products: injectable collagen for soft tissue augmentation (Webster et al., 1984);
collagen-based artificial skins (Bell et al., 1981; Yannas and Burke, 1981). Research and
Development: collagen-based wound dressings (Armstrong et al., 1986)
Cardiovascular surgery
and cardiology
Commercial products: collagen-coated and gelatin-coated vascular grafts (Jonas et al., 1988;
Li, 1988), chemically processed human vein graft (Dardik et al., 1974), bovine arterial grafts
(Sawyer et al., 1977), porcine heart valves (Angell et al., 1982), bovine pericardial heart valves
(Walker et al., 1983), and vascular puncture hole seal device (Merino et al., 1992)
Neurosurgery
Research and development: guiding peripheral nerve regeneration (Archibald et al., 1991;
Yannas et al., 1985) and dura replacement material (Collins et al., 1991)
Periodontal and oral
surgery
Research and development: collagen membranes for periodontal ligament regeneration
(Blumenthal, 1988), resorbable oral tissue wound dressings (Ceravalo and Li, 1988), and
collagen/hydroxyapatite for augmentation of alveolar ridge (Gongloff et al., 1985)
Ophthalmology
Commercial products: collagen corneal shield to facilitate epithelial healing (Ruffini et al., 1989).
Research and development: collagen shield for drug delivery to the eye (Reidy et al., 1990)
Orthopedic surgery
Commercial products: collagen with hydroxyapatite and autogenous bone marrow for bone
repair (Hollinger et al., 1989). Research and development: collagen matrix for meniscus
regeneration (Li et al., 1994), collagenous material for replacement and regeneration of
Achilles tendon (Kato et al., 1991), and reconstituted collagen template for anterior cruciate
ligament (ACL) reconstruction (Li et al., 1997)
Other applications
Research and development: drug delivery support (Sorensen et al., 1990), delivery vehicles for
growth factors and bioactive macromolecules (Deatherage and Miller, 1987; Li et al., 1996),
and collagenous matrix for delivery of cells for tissue and organ regeneration (Bell et al., 1981)
