Biomedical Engineering Reference
In-Depth Information
et al. 2004; Sun, Moffat, and Lu 2007). Specifi cally, FTIR-I analysis of the interface
found that calcium phosphate presence was only detected at the mineralized
fi brocartilage and bone regions (Figure 17.3C). It is likely that the measured
increase in elastic modulus is directly related to the presence of calcium phos-
phate within the mineralized fi brocartilage region of the interface. It has been
suggested that the quantity of calcifi ed tissue at the insertion may be positively
correlated to the force transmitted across the calcifi ed zone (Benjamin, Evans,
Rao, Findlay, and Pemberton 1991), and warrants further evaluation. In addition
to the mineral phase, large extracellular matrix molecules such as collagen
or proteoglycans are also expected to play a role in maintaining the structure-
function profi les at the soft tissue-to-bone interface, and should be further
investigated.
In summary, theoretical and experimental evaluations of the interface
suggest that a structure-function relationship exists at the ligament-to-bone
insertion. As such, more in-depth determination of the chemical and mechanical
properties of the insertion at the nano-, micro-, and macro-scale levels are needed
for providing key design parameters for interface tissue engineering. The devel-
opment and application of novel characterization methods with the requisite
resolution to quantify both structural and functional variations across multi-
tissue regions will be essential for augmenting the current understanding of this
complex interface.
17.5 MULTI-PHASED SCAFFOLD DESIGN FOR INTERFACE
TISSUE ENGINEERING
Investigations of the role of heterotypic cellular interactions in interface regen-
eration, as well as interface structure-function relationships, are invaluable for
biomimetic scaffold design in orthopedic interface tissue engineering. It is likely
that interface formation will require
multiple types
of cells, a
scaffold
system
which supports interactions between different cell types, and the development of
distinct yet continuous
multi - tissue regions
through physical and biochemical
stimuli. Therefore, the design of biomimetic, multi-phased scaffolds able to
promote heterotypic cellular interactions and multi-tissue formation will be criti-
cal for interface tissue engineering.
Stratifi ed scaffold design has been researched for orthopedic tissue engineer-
ing, and in particular for osteochondral applications (Gao et al. 2001; Hollister,
Maddox, and Taboas 2002; Lu et al. 2005; Niederauer et al. 2000; Schaefer et al.
2000; Yu, Grynpas, and Kandel 1997). The fi rst generation of the stratifi ed scaf-
folds were formed by joining together two different scaffold phases by sutures or
sealants. Schaefer et al. (Schaefer, Martin, Shastri, Padera, Langer, Freed, and
Vunjak-Novakovic 2000) seeded bovine articular chondrocytes on PGA meshes
and periosteal cells on PLGA/polyethylene glycol foams, and subsequently
sutured these separate constructs together at one or four weeks after seeding.
Integration between the two scaffolds was observed to be superior when brought
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