Biomedical Engineering Reference
In-Depth Information
Figure 7.1.
The foreign body reaction towards implanted biomaterials. 1) A biomaterial
is implanted and damage to surrounding tissue occurs. 2) In seconds to minutes, non-spe-
cifi c proteins from body fl uids are adsorbed on the implant surface. 3) Neutrophils and
macrophages try to interrogate the material. 4) Failing to interrogate the material, cells fuse
to form giant cells and concurrently secrete cytokines to signal other kinds of cells. 5) and
6) Fibroblasts arrive and fabricate a collagenous bag to insulate the material from the
surrounding tissue. Fig. adapted from [19].
that the implant is completely encapsulated in an acellular, avascular collagen bag
about 50-200 micrometers thick [19]. The fi brous capsule prevents suffi cient
bonding between an implant surface and juxtaposed bone and frequently leads to
clinical failure of orthopedic implants. Consequently, repelling fi broblasts that
can cause an infl ammatory reaction is necessary at the surface of a newly
implanted orthopedic device [9]. Controlling protein adsorption by surface
modifi cation is an effective method for attracting desirable cells onto the implant
surface and minimizing the functions of fi broblasts, such as their adhesion and
secretion of fi brous tissue [9,20].
Therefore, numerous research efforts in bone tissue engineering have
focused on surface modifi cation (or altering the implant surface topography and
chemistry of implant materials, including the development of novel nanophase
materials “that is, materials with basic structural units, grains, particles, fi bers or
other constituent components in the range of 1-100 nm [42]” such as nanophase
metals, ceramics, and polymers, and so on. These materials have been critical in
the overall design and synthesis of bone-like composites which possess not only
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