Biomedical Engineering Reference
In-Depth Information
the conversion of fibrinogen to fibrin monomers by thrombin, and
gelation occurs quickly within 30
∼
60 seconds. One advantage of
using fibrin in this manner is the ability to completely fill the defect
bygelling
insitu
.Afibrinsealantcomposedoffibrinogenandthrom-
bin in addition to antifibronolytic agents has been already used in
surgical application for sealing lung tears, cerebrospinal fluid leaks,
and bleeding ulcer because of its natural role in wound healing. A
fibrin sealant might be made from autologous blood as the patient's
own blood or from recombinant proteins.
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Fibrin gels can degrade
either through hydrolytic or through proteolytic means. Fibrino-
gen is commercially available from several manufacturers, result-
ing in relatively low cost of fabrication of fibrin gels. More recently,
many works have been done in the development fibrin as a poten-
tial tissue engineering scaffold matrix, especially cartilage formed
from a fibrin/chondrocyte construct. Biochemical and mechani-
cal analysis demonstrated cartilage-like properties. A fibrin/PLGA
hybrid composite has been investigated to optimize the reduction
of inflammatory reaction of PLGA for the application of tissue-
engineered cartilage and intervetebral disc substitutes, as shown in
chapter 16.
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1.2.4.2 Collagen
At least 22 types of collagen exist in the human body. Among these,
collagen types I, II, and III are the most abundant and ubiquitous
kind.Theconformationofthecollagenchainistriplehelicesthatare
packedorprocessedintomicrofibrils.Molecularly,thethreerepeat-
ing amino acid sequences, such as glycine, proline, and hydrox-
yproline, form protein chains, resulting in the intertwinement in
a triple-helix arrangement. Type I collagen is the most abundant
and is the major constituent of bone, skin, ligament, and tendon,
whereas type II collagen is a major collagen in cartilage. Collagen
can promote cell adhesion, as demonstrated by the Asp-Gly-Glu-Ala
peptide in type I collagen that functions as a cell-binding domain.
Due to the abundance and ready accessibility of these tissues,
they have been frequently used as a source for the preparation of
collagen.
1
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