Biomedical Engineering Reference
In-Depth Information
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interesting because their surfaces may contain reactive
groups
de novo,
or they may be readily derivatized with
reactive groups that can be used to covalently link bio-
molecules. Another advantage of polymers as supports
for biomolecules is that the polymers may be fabricated
in many forms, including films, membranes, tubes,
fibers, fabrics, particles, capsules, and porous structures.
Furthermore, polymer compositions vary widely, and
molecular structures include homopolymers, and
random, alternating, block, and graft copolymers. Living
anionic polymerization techniques, along with newer
methods of living free radical polymerizations, now
provide fine control of molecular weights with narrow
distributions. The molecular forms of solid polymers
include un-cross-linked chains that are insoluble at
physiologic conditions, cross-linked networks, physical
blends, and IPNs (e.g.,
Piskin and Hoffman, 1986
;see
also Section 3.2.2). When surfaces of metals or inorganic
glasses or ceramics are involved, biological functionality
can sometimes be added via a chemically immobilized or
physisorbed polymeric or surfactant adlayer, or by use of
techniques such as plasma gas discharge to deposit
polymer compositions having functional groups (see also
Section 3.2.14).
3.2.16 Surface-immobilized
biomolecules
Allan S. Hoffman and Jeffrey A. Hubbell
Biomolecules such as enzymes, antibodies, affinity pro-
teins, cell receptor ligands, and drugs of all kinds have
been chemically or physically immobilized on and within
biomaterial supports for a wide range of therapeutic,
diagnostic, separation, and bioprocess applications. Im-
mobilization of heparin on polymer surfaces is one of the
earliest examples of a biologically functional biomaterial.
Living cells may also be combined with biomaterials, and
the fields of cell culture, artificial organs, and tissue en-
gineering are additional, important examples. These
''hybrid'' combinations of natural and synthetic materials
confer ''biological functionality'' to the synthetic bio-
material. Since many sections in this text cover many
aspects of this topic, including adsorption of proteins and
adhesion of cells and bacteria on biomaterial surfaces,
NFSs, cell culture, tissue engineering, artificial organs,
drug delivery, and others, this section will focus on the
methodology involving physical adsorption and chemical
immobilization of biomolecules on biomaterial surfaces,
especially for applications requiring bioactivity of the
immobilized biomolecule.
Among the different classes of biomaterials that
could be biologically modified, polymers are especially
Patterned surfaces
Biomaterial surfaces may be functionalized uniformly or
in geometric patterns (
Bernard
et al.,
1998; Blawas and
