Civil Engineering Reference
In-Depth Information
good integration into host tissue, and l exibility of production in various shapes and
sizes. Since microbial cellulose consists of a highly entangled network of i brils, it also
provides the material with strong mechanical properties, which are essential for tissue-
engineered blood vessels to withstand mechanical forces and to prevent rupture. h e
microbial cellulose can be designed and shaped into three-dimensional structures such
as tubes or sheets. A major advantage of using microbial cellulose instead of cellulose
produced by any other organisms/plants is that microbial cellulose is completely free
from biogenic compounds such as lignin, pectin and arabinan found in eggplant cellu-
lose. During the production process, it is also possible to modify several other proper-
ties including pore size, surface properties and layering of the material [100].
Several studies have shown that microbial cellulose can be molded into tubular form
with diameter < 6 mm. Klemm
et al.
[101] prepared a microbial cellulose tube having
1 mm diameter and 5 mm length with a wall thickness of 0.7 mm. h e tensile strength
of the material was found to be comparable to that of normal blood vessels (800 mN)
and is employed as blood vessel to replace part of the carotid artery. At er four weeks,
the microbial cellulose/carotid artery complex was covered with connective tissue. h e
in-vivo
bicompatibility tests show that microbial cellulose can be used as a replace-
ment blood vessel. Recently, Brown
et al.
[102] have prepared small tubes of microbial
cellulose-i brin composites treated with glutaraldehyde in order to crosslink the poly-
mers and allow a better match of the mechanical properties with those of native small-
diameter blood vessels.
BASYC®, the well-known microbial cellulose-based blood vessels, was tubu-
larly designed by Klemm
et al.
directly during cultivation with the aim of developing
biomaterials for medical application [101]. h ese formed artii cial blood vessel inter-
positions with inner diameter of about 1 mm and 0.7 mm wall thickness products were
applicated as covers in experimental micronerve surgery. Inspection at er four weeks
of the treated vessel showed that carotid artery-BYSYC-complex was wrapped up with
connective tissues, pervaded with small vessels like vasa vasorum. h e study proved that
BASYC-interposition can be completely incorporated in the body without any rejection
reaction. h e vessel also showed high mechanical strength in wet state, enormous water
retention values, low roughness of the inner surface, and a complete "vitalization" of
BASYC microvessel-interpositions in rat experiments demonstrate the high potential
of BASYC as an artii cial blood vessel in microsurgery. Later in 2009, Schumann
et
al.
tested novel styled microbial cellulose BASYC by attaching the implants in an arti-
i cial defect of the carotid artery for a year in rats and used it to replace the carotid
arteries of pigs [103] . h e long-term results with BASYC vessels show the incorpora-
tion of the microbial cellulose under formation of neointima and ingrowth of active
i broblasts. Also, these BASYC vessels were shown to be stable vascular conduits and
were biocompatible. Moreover, the morphological analysis carried out showed that
structural modii cation in the contact region between the BASYC blood vessels and the
surrounding media had occurred. h e presence of i broblasts in this region suggests
that a process of integration without degradation (vitalization) has taken place.
h e potential use of microbial cellulose-based composites for the production of heart
valve replacements is currently under study. Milton
et al.
[104] and Mohammadi
et al.
[105] prepared biocompatible microbial cellulose-poly(vinyl alcohol) nanocomposite
for the production of heart valve leal ets. h e nanocomposite prepared by Millon and
